False Elevation Research Articles

Troponin Test, Not Only a Number: An Unusual Case of False Positive

Heterophile antibodies, which can arise from infections, autoimmune disorders, or exposure to animal antigens, can interfere with immunoassays. These antibodies can cross-react with the test reagents used in troponin assays, causing a false elevation in troponin levels. The paper describes a case of a 37-year-old male drug abuser admitted to the emergency room with chest pain. A series of troponin measurements performed using different assays gave discrepant results. Only thanks to the use of Scantibodies HBT tubes, which remove heterophile antibodies, was it possible to make a correct diagnosis of troponin negativity. In conclusion, a correct laboratory/clinical approach to the identification of heterophile antibody interference is essential for accurate troponin testing in order to avoid false positive results. Implementing neutralizing tests can significantly improve the reliability of these diagnostic assays, ensuring better patient outcome.

Safety of single-dose bedaquiline combined with rifampicin for leprosy post-exposure prophylaxis: A Phase 2 randomized non-inferiority trial in the Comoros Islands.

To reduce leprosy risk in contacts of patients with leprosy by around 50%, the World Health Organization (WHO) recommends leprosy post-exposure prophylaxis (PEP) using single-dose rifampicin (SDR). Results from a cluster randomized trial in the Comoros and Madagascar suggest that PEP with a double dose of rifampicin led to a similar reduction in incident leprosy, prompting the need for stronger PEP. The objective of this Phase 2 trial was to assess safety of a bedaquiline-enhanced PEP regimen (intervention arm, bedaquiline 800 mg with rifampicin 600 mg, BE-PEP), relative to the WHO recommended PEP with rifampicin 600 mg alone (control arm, SDR-PEP). From July 2022 to January 2023, consenting participants were screened for eligibility, including a heart rate-corrected QT interval (QTc) <450 ms and liver enzyme tests (ALT/AST) below 3× the upper limit of normal (ULN), before they were individually randomized 1:1 in an open-label design. Recruitment was sequential, by age group. Pediatric dosages were weight adjusted. Follow-up was done at day 1 post-dose (including ECG) and day 14 (including ALT/AST), with repeat of ALT/AST on the last follow-up at day 30 in case of elevation on day 14. The primary outcome was non-inferiority of BE-PEP based on a <10 ms difference in QTc 24 h after treatment administration, both unadjusted and adjusted for baseline QTc. Of 408 screened participants, 313 were enrolled, starting with 187 adults, then 38 children aged 13 to 17 years, and finally 88 children aged 5 to 12 years, of whom 310 (99%) completed all visits. Across all ages, the mean QTc change on BE-PEP was from 393 ms to 396 ms, not significantly different from the change from 392 ms to 394 ms on SDR-PEP (difference between arms 1.8 ms, 95% CI -1.8, 5.3, p = 0.41). No individual's QTc increased by >50 ms or exceeded 450 ms after PEP administration. Per protocol, all children were analyzed together, with no significant difference in mean QTc increase for BE-PEP compared to SDR-PEP, although non-inferiority of BE-PEP in children was not demonstrated in unadjusted analysis, as the upper limit of the 95% CI of 10.4 ms exceeded the predefined margin of 10 ms. Adjusting for baseline QTc, the regression coefficient and 95% CI (3.3; -1.4, 8.0) met the 10 ms non-inferiority margin. No significant differences in ALT or AST levels were noted between the intervention and control arms, although a limitation of the study was false elevation of ALT/AST during adult recruitment due to a technical error. In both study arms, one serious adverse event was reported, both considered unlikely related to the study drugs. Dizziness, nausea, headache, and diarrhea among adults, and headaches in children, were nonsignificantly more frequently observed in the BE-PEP group. In this study, we observed that safety of single-dose bedaquiline 800 mg in combination with rifampicin is comparable to rifampicin alone, although non-inferiority of QTc changes was demonstrated in children only after adjusting for the baseline QTc measurements. A Phase 3 cluster randomized efficacy trial is currently ongoing in the Comoros. ClinicalTrials.gov NCT05406479.

Buffy coat removal to mitigate reporting false normal G6PD phenotype results in patients undergoing rasburicase therapy for tumor lysis syndrome

Abstract Glucose-6-phosphate dehydrogenase (G6PD) is the primary source of NADPH in red blood cells (RBCs). NADPH reduces reactive oxygen species (ROS) thereby protecting RBCs from oxidative stress-mediated hemolytic anemia (HA). Individuals with partial or full G6PD deficiency are therefore susceptible to acute HA provoked by medications that generate high ROS loads in vivo, e.g., rasburicase. Rasburicase is an enzyme-based therapeutic used to degrade uric acid (UA) in patients with tumor lysis syndrome (TLS); however, catalysis of UA generates H2O2, a potent ROS, which poses a risk of HA in individuals who are deficient in G6PD activity. Screening G6PD activity prior to rasburicase administration is clinically indicated in ethnic groups with high rates of G6PD deficiency, although reports of HA in rasburicase-treated patients have been reported across low prevalence ethnic groups as well. TLS occurs most commonly during the treatment of highly proliferative neoplasms, such as leukemia and lymphoma. Since WBCs contain significant G6PD activity, an elevated WBC count in these patients can cause the false assurance of low HA risk due to a falsely normal G6PD activity. We sought to establish and evaluate a novel method to mitigate WBC contamination of G6PD measurements in patients undergoing rasburicase therapy. In this study, we first developed and validated an innovative method (“piercing method”) to minimize the interference of WBCs in G6PD measurements. The piercing method demonstrated acceptable accuracy (slope: 1.008; bias: -6.22%) and precision (1.4% CV between 9.9 to 20.7 U/g Hb) and was effective at eliminating a broad range of WBC types and concentrations from whole blood samples (N = 85, tested range = 0.31 – 413.05 K/μL, 93% reduction in WBCs). We compared G6PD activity in rasburicase-treated patients (N = 39) with varying WBC counts before and after buffy coat removal using the piercing method. Average percent change in G6PD activity (post-pierce – pre-pierce) between patients with and without elevated WBCs was substantial (45% versus 12%). In comparing G6PD activity in patients before and after the initiation of rasburicase therapy, there is no evidence that in vivo-generated ROS from rasburicase affect G6PD measurement in vitro in an assay that relies on monitoring absorbance of NADPH (22.2 U/g Hb versus 22.9 U/g Hb, p=0.721). Results demonstrate how WBCs increase risk for false elevation in G6PD activity in patients being considered for rasburicase therapy. At greatest risk are patients with partial G6PD deficiency, e.g., heterozygous females, where G6PD from WBCs could mask deficiency. Literature describing testing of G6PD in specimens with elevated WBCs is lacking. This study shows that the piercing method provides accurate G6PD results in samples with elevated WBCs from patients at risk of TLS, who might develop HA after starting rasburicase therapy.

Utility of Reticulocyte Hemoglobin Equivalent in Screening for Iron Deficiency in Pregnancy.

Ferritin, commonly used for diagnosing iron deficiency (ID) in pregnancy, is limited by high cost and false elevations during inflammation. Reticulocyte hemoglobin equivalent (Ret-He), an alternative marker for ID, is unaffected by inflammation and analyzed on the same collection tube as the standard complete blood count (CBC). We aimed to determine the accuracy of Ret-He in detecting ID in pregnancy compared to ferritin in a U.S. This prospective cohort study enrolled 200 pregnant participants, recruited in any trimester if a CBC was drawn as part of routine prenatal care. For those who agreed to participate, Ret-He and ferritin were collected concurrently with the CBC. ID was defined as ferritin level below 30 ng/mL. Patients were classified into three groups based on hemoglobin and ferritin results to determine the severity of ID: no ID, ID alone, and ID anemia (IDA). Four participants with anemia but normal ferritin were excluded. Receiver operating curve analysis, including the area under the curve (AUC), was performed to assess the accuracy of Ret-He in detecting ID. A one-way ANOVA (analysis of variance) with post-hoc analysis was used to compare differences in Ret-He between the three groups of ID severity. The prevalence of ID in our cohort was 82% (161/196). The AUC for Ret-He was 0.65 (95% confidence interval: 0.55-0.75), indicating suboptimal discrimination between patients with and without ID. Ret-He was significantly different among the three groups (p < 0.001). In post-hoc analysis, Ret-He was significantly lower in the IDA group compared to the ID group (p < 0.001) but there was only a trend of lower Ret-He in the ID group compared to the non-ID group (p = 0.38). Ret-He has low accuracy in diagnosing ID in pregnancy. It may be useful in detecting severe ID resulting in anemia but not a mild iron-deficient state resulting in ID only. · The prevalence of ID in our cohort was 82%.. · Ret-He has low accuracy in diagnosing ID in pregnancy.. · Ferritin is preferable when readily available..

7874 Management Of “Hyperandrogenism” Confounded By Dermatology Biotin Prescriptions

Abstract Disclosure: S.S. Sundar: None. S. Shankar: None. M.S. Vaishnav: None. L. Lekkala: None. S. Sathyanarayana: None. C. Siddlingappa: None. K. M: None. T.-. Kamala: None. R.B. V: None. V. Nath: None. M.D. Chitra: None. P. Ravikumar: None. Introduction: Immunoassay interferences include: Cross-reactions, heterophile antibodies, biotin and anti-analyte antibodies, with positive or negative bias, leading to difficulties in clinical decision-making (confounding diagnosis, unnecessary investigations or inappropriate treatments). The interfering substance may be exogenous (e.g., drug or substance absorbed by patient) or endogenous (e.g., antibodies produced by patient). Clinical Case 2023 Dec 1 Dermatology management for hyperandrogenism 28-year-old female evaluated for acne 3 years (increased 4 months), hair fall 6 months and hirsutism 3 years (threading) Total Testosterone 443 ng/dL (10-55) CLIA Free Testosterone 8.9 pg/mL (0.1-6.4) ELISA DHEAS 209 µg/dL (35-430) CLIA S Cortisol 8 am 6.9 µg/dL (2.6-10.5) CLIA LH 4.2 mIU/mL (1.9-12.5); FSH 5.3 mIU/mL (3.0-8.0) T3 133 ng/dL (80-200); T4 8.5 ug/dL (4.8-12.7), TSH 3.78 µIU/mL (0.5-5.3) HbA1c 5.0%; Glucose fasting 81 mg/dL; Insulin fasting 39.4 mU/L (3-25); HOMA-IR 5.2; HOMA%B 380; HOMA%S 19.2; T3 133 ng/dL (80-200) 2023 Dec 14 Endocrinology for “scaringly” very high testosterone levels Menstrual history: Menarche 11 years; Cycles regular. Unmarried Family history: Diabetes++; Hirsutism+; Infertility- Physical exam: Height 159 cm; Weight 55 kg; BMI 21.8 kg/m2; Ferriman Gallwey score 11; Pulse 75; BP 79/62; Thyroid: Grade 0. In view of total testosterone levels in “neoplastic androgen excess” range, further endocrinology evaluations (multiple labs and assays) were carried out. However, discordance between the mild clinical versus severe biochemical hyperandrogenism was noted. Review of the dermatology prescription indicated that patient had consumed only one 10 mg tablet of biotin 36 hours before the earlier blood draw obtained by dermatologist. Total Testosterone 22.3 and 33.8 ng/dL (6-82) ECLIA; 19.7 (15-70) LCMS Free Testosterone 0.69 pg/mL (&amp;lt; 2.85) (ELISA) DHEAS 101 µg/dL (45-380) LCMS Androstenedione 104 ng/dL (75-205) LCMS 17OH Progesterone 0.89 ng/mL (0.16-2.05) EIA; 0.40 (0.35-2.9) LCMS S Cortisol 5.92 ug/dl (6-18) ECLIA; 5.45 (5-23) LCMS FSH 2.74; LH 6.07; Prolactin 20.1 ng/mL (4.7-23.3) T3 114 ng/dL; T4 7.2 µg/dL; TSH 1.29 Diagnosis Falsely elevated total testosterone (and free testosterone) levels due to biotin immunoassay interference. Clinical Lessons: Very limited studies exist confirming the exact clinical indications for biotin (eg: improvement of hair quality or quantity, or nail growth). FDA warning highlights biotin’s interference (false elevations or reductions) with immunoassays relying on biotin-streptavidin technology. Physicians must ask patients about supplement usage, and discontinue biotin for 8 hours for patients taking 10 mg/day, 3 days for 100-300 mg/day, 7 days for children taking 2 and 15 mg/kg/daily, and inform laboratory if diagnostic test was performed while taking biotin. Presentation: 6/2/2024

A-115 Iron assay improvement: The need for thiourea addition in Ferene/Ferrozine reagent cartridge

Abstract Background Iron assay is often ordered along with ferritin, transferrin, and iron binding capacity in patients suspected of having iron deficiency anemia or iron overload. A ferene/Ferrozine chromogen-based iron assay is more common in College of American Pathology accredited laboratories across U.S. Recently, a product recall/field safety notice was issued by a major manufacturer for several lots of ferene based iron reagent due to unacceptable positive bias in patient iron results. However, the reason(s) underlying this positive bias was not provided. In this report, we investigated the possible causes for the recall of specific lots of iron assay reagents. Methods The performance of 2 lots of recalled iron test kits was compared against 2 good lots (Sentinel Diagnostics) on the Alinity c analyzer utilizing approved calibrator lots, quality control (QC) materials (Bio-Rad Laboratories), and excess/leftover de-identified patient samples. Spectral scan (in the visible wavelength) of good and recalled lots of reagents, R1 and R2 was performed on the Tecan microplate reader. Trace elements in R1 and R2 reagents were estimated with Quantitative Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Spiking experiments in calibrator, discarded patient samples, and reagents were undertaken to further elucidate the cause and prevention of positive bias seen with recalled reagent lots. Graphs and statistical analysis were generated using Graphpad prism 10.1. Results Iron levels in QC materials and de-identified patient samples (n=42) tested with 2 recalled lot of reagents on Alinity c analyzer showed a positive bias of 15-36% compared to unimpacted lots of reagents. Calibrator and blank absorbance of recalled lots was much higher than the unimpacted lots. Percentage change in the basal absorbance of recalled vs unimpacted R2 reagent measured from 500 to 600 nm in 25 nm increments and corrected to 700 nm ranged from 150 to 250%. No such changes were noted with both R1 reagents. Interestingly, ICP-MS heavy metal panel analysis revealed that R2 reagent of the recalled lots had unanticipated presence of Cu (∼22 υg/dL) and lead (7.5 υg/L), which was not present in R1 reagents. Increased concentrations of Cu spiking (100, 200, and 400 υγ/dL) in R2 reagent from recalled lots discernibly increased the Cal Factor values as well as patient iron results relative to unspiked reagent. Further, the presence of Cu over time deteriorated the accuracy of R2 reagent reflecting on very high rise in Cal Factor and patient iron values. Interestingly, TU addition to R2 reagent from unimpacted lot prevented the Cu-induced spurious rise in Cal Factor and iron measurements in the patient samples. Further, TU exhibited sustained preventive effect on Cu-induced iron measurement changes over time. Conclusions Based on our investigation, we conclude that copper contamination of R2 reagent is the possible cause for the positive bias in the recalled iron assay reagent lots. We recommend the addition of TU to Ferene containing R2 reagent pack as a simple and effective step to prevent Cu-induced false elevation in iron values.

Macro-FSH is a rare cause of inappropriately high FSH concentrations.

Assessment of hormone concentrations can be subjected to laboratory pitfalls. Macro-hormones are hormone-autoantibody complexes which are cleared slowly from circulation and cause a false elevation in hormones' concentrations. Macro-prolactin and macro-thyroid-stimulating hormone (TSH) are most frequently encountered while macro-follicle-stimulating hormone (FSH) has been rarely reported. We describe the case of a 30-year-old woman who had a gynaecological consultation due to failure in achieving pregnancy after 8 months of unprotected intercourse. She had regular menses, did not complain of climacteric symptoms and her medical history was unremarkable. Antral follicle count and anti-mullerian hormone concentrations were normal, and regular ovulation was documented. Unexpectedly, high early follicular phase FSH concentrations were confirmed on two occasions (57 and 51 IU/L), raising the suspicion of primary ovarian insufficiency. After excluding Turner's syndrome and autoimmune oophoritis, a laboratory artifact was hypothesized. Following polyethylene glycol precipitation, FSH levels dropped from 41.1 IU/L to 6.54 IU/L (recovery 16%) and the presence of macro-FSH was concluded. Laboratory interference can lead to misdiagnosis and unnecessary treatments. A laboratory artifact should be suspected when inconsistency exists between clinical presentation and laboratory results. Only five other cases of macro-FSH have been reported to date. Although macro-hormones generally have low biological activity and do not require treatment, the role of anti-FSH antibodies has been hypothesized in primary ovarian insufficiency and in vitro fertilization failure. Hormone quantification is a cornerstone in the diagnostic workup of endocrine disorders, but it can be subjected to laboratory interferences which can lead to unnecessary investigations and inappropriate treatments. A laboratory artifact should be suspected when a discrepancy is observed between clinical presentation and laboratory results, when extremely unusual analyte concentrations are observed and when inconsistent results are obtained by different analytical methods. Macro-hormones are hormone-autoantibody complexes which are cleared slowly from circulation and cause a false elevation in hormone concentrations. Macro-prolactin and macro-TSH are most frequently encountered, while macro-FSH has been rarely reported. Macro-hormones can be detected by polyethylene glycol precipitation, gel filtration chromatography, or by using protein G or protein A columns. Although macro-hormones generally have low biological activity and do not require treatment, the role of anti-FSH antibodies has been hypothesized in primary ovarian insufficiency and in vitro fertilization failure.

Recent Recall of Iron Reagent-Investigation of Potential Reagent Contamination and Assay Improvement Strategy.

Recently, a major manufacturer recalled several lots of iron assay reagent due to positive bias of roughly 15%-30% and the cause remains unknown. This study investigated the root cause of this positive bias and evaluated a simple practical approach to improve the assay. Performance comparison of recalled and unimpacted iron assay kits was done utilizing calibrators, quality control (QC) materials, and 42 remnant patient samples. Spectral scan and trace elements analysis of R1 and R2 reagents was performed. Copper (Cu) and thiourea (TU) spiking experiments were utilized to elucidate the cause and prevention of positive bias seen with recalled lots. Iron measurements in QC materials and patient samples using recalled reagents generated a positive bias of 17.5% and 21%, respectively. Correspondingly, the recalled R2 reagents, but not R1, showed a rise in basal absorbance along with an unanticipated presence of Cu (22.7 µg/dL) and lead (7.5 µg/L). Cu spiking to recalled and unimpacted R2 reagent intensified the reagent color besides falsely increasing its absorbance, calibration factor, and patient iron measurements. Interestingly, addition of TU (65 mmol/L) to R2 reagent from unimpacted lot prevented the short-term and prolonged Cu-induced spurious rise in calibration factor and patient iron estimations. We conclude that accidental copper contamination of R2 reagent during manufacturing could be a reason underlying the positive bias in the recalled iron reagent lots. Addition of TU in ferene-containing R2 reagent is a simple and effective means to prevent Cu-induced false elevation in iron values.

P-39 Fictitious hyperestrogenism in perimenopause: Difficulties in diagnosis by laboratory pitfalls

Abstract Introduction Laboratory errors related to interfering substances can cause significant morbidity related to unnecessary investigations and interventions and patient anxiety. Estradiol (E2) is quantified mainly with competitive immunoassays. The prevalence of analytical interference can be up to 6% and is due to the impairment of the interaction between test antibody and analyte, causing falsely elevated levels. Nevertheless, interference due to heterophile antibody is extremely rare. Clinical Case A 51-year-old woman, normal weight, nulliparous, irrelevant previous medical history, menarche at 12 years old and regular menstrual cycles, was referred to the Endocrinology Department due to elevated E2 level. She was followed 4 years before in another institution with no formal diagnosis complaining of severe vasomotor symptoms, vaginal dryness and menometrorrhagias. She was on combined oral contraceptives for 10 years as a method of contraception, which she stopped two years ago. The first two E2 random values were 2362 and 3121 pmol/L, respectively when she had 47 and 49 years old. During our evaluation in January 2021, at the age of 51 years old, in the 4th day of her menstrual cycle, the laboratory evaluation revealed: FSH 9.56 mUI/mL (2.5-10.2), LH 5.43 mUI/mL (1.9-12.5), Prolactin 18.12 ng/mL (2.8-29.2), E2 3530.51 pmol/L (71.6-529.2), 17-Hydroxiprogesterone 0.52 ng/mL (0.32-1.47), DHEA-SO4 75.9 ug/dL (35-430), 4-Androstenedione 1 ng/mL (0.3-3.3) and SHBG 137 nmol/L (18-144). Transvaginal pelvic ultrasonography performed 15 days after menstrual period revealed 2 subserous leiomyomas, a 12 mm endometrial line and a right ovary with a pre-ovulatory follicle. CT scan of adrenal glands was unremarkable and a sellar MRI revealed a 4mm area of hypocaptation in the left region of the adenohypophysis. During this period the patient was treated with escitalopram 10 mg od, with vasomotor symptoms improvement. Two years later, after a 6-month period of amenorrhea, she repeated the analytical evaluation that revealed raised gonadotropins levels (FSH 102.12 mUI/mL, LH 25.37 mUI/mL), low progesterone 0.91 mUI/mL (&amp;lt; 4.45) but maintained a largely elevated estradiol level (1128.01 pmol/L) with undetectable free Estriol (&amp;lt; 0.10 ng/mL). This pattern motivated laboratorial review of blood samples by mass spectrometry and not by chemiluminescence as before. The value was substantially lower (447 pmol/L) hypothesizing the presence of heterophilic antibodies. Conclusion Although false E2 elevation due to analytical interference is rare, it must be suspected when results are discordant with the clinical picture and there is no evidence of neoplastic disease. Here, we report a case of falsely elevated E2 that led to prolonged investigation and major impact on a female's quality of life during the challenging period of perimenopause.

Alfaxalone increases measured progesterone concentration in neutered male cats when determined by immunoreactivity.

Alfaxalone is a commonly used anesthetic agent in small animals. In cats, alfaxalone can be administered as an IM agent to achieve clinically useful sedation or anesthesia, negating the need for IV injection in difficult patients. The molecular structure of alfaxalone is similar to the hormone progesterone (P4). It is hypothesized that alfaxalone would cross-react with the assay measuring progesterone causing a false elevation. 8 healthy neutered male, domestic shorthair cats that were privately owned were enrolled in the study. Male neutered cats were administered 3 mg/kg of alfaxalone IM. Blood samples were collected at set time points (baseline, 30 minutes, 60 minutes, 3 hours, 6 hours, and 10 hours after administration), and serum concentrations of progesterone immunoreactivity (IR) were determined using the Siemens Immulite 1000 automated immunoassay system. Statistical analysis was performed with repeated measures ANOVA and a Tukey-Cramer multiple comparisons test. A P value of < .05 was used for significance. Serum progesterone IR was significantly elevated at 30 minutes, 1 hour, and 3 hours (P < .05) when compared to baseline progesterone immunoreactivity. Progesterone immunoreactivity had returned to baseline by 6 hours. This study suggests that alfaxalone administered IM in cats may interfere with immunoassay measurement of serum progesterone for up to 6 hours. Caution should be used when interpreting serum progesterone immunoreactivity results in cats within 4 hours of alfaxalone.

Unexplained increases in serum carcinoembryonic antigen levels in colorectal cancer patients during the postoperative follow-up period: an analysis of its incidence and longitudinal pattern

Background Carcinoembryonic antigen (CEA) monitoring facilitates the detection of recurrence in patients with colorectal cancer (CRC) after resection. False-positive CEA has been reported in CRC patients with certain comorbidities or smokers. However, limited information is currently available on the frequency of and changes in falsely elevated CEA levels in patients without these conditions. Materials and methods We retrospectively examined CRC patients who underwent surgical resection at our hospital between 2001 and 2017, had no recurrence for at least five years, and were free of known factors that may increase CEA. Postoperative CEA levels were retrieved until 2 years before the last contact. For comparison, we similarly selected patients who developed recurrence after resection of CRC during the same period, and CEA levels at initial presentation, at nadir, and at the time of recurrence were reviewed. The patterns of elevated CEA (>5 ng/ml) were classified as transient, repeated, or persistent based on longitudinal changes. The relationships between CEA and carbohydrate antigen 19-9, transaminases, creatinine, and C-reactive protein were examined. Results CEA elevation occurred in 90 (20%) out of 446 eligible patients without recurrence at least once during the mean postoperative period of 50.5 months, whereas CEA was >5 ng/ml in 117 (53%) of 221 patients when they developed recurrence. Twenty-seven patients without recurrence showed a transient elevation in CEA, 45 repeated elevations, and 18 a persistent elevation; the frequency of a high preoperative CEA level increased in this order. The majority (98%) of false elevations ranged between 5 and 15 ng/ml. CEA was not associated with other laboratory data. Conclusions Unexplained CEA elevations were observed in 20% of recurrence-free CRC patients after surgery, and were classified into three patterns based on longitudinal changes. A more detailed understanding of patient-specific fluctuations in CEA will prevent unnecessary imaging studies and reduce medical costs.

Pseudohyperkalemia Revisited: An Updated Review of a Foremost Preanalytical Error of Serum or Plasma Potassium Measurement in the Clinical Laboratory

Abstract Background: Potassium is one of the most abundant cations in the human body. Increased plasma potassium concentration (hyperkalemia) is one of the most common electrolyte abnormalities in contemporary clinical practice. Moderate and severe hyperkalemia are potentially life-threatening conditions and constitute medical emergencies. Measured hyperkalemia may be true hyperkalemia or false hyperkalemia (pseudohyperkalemia). Pseudohyperkalemia is due to false elevation of measured potassium concentration in vitro and it is a fairly common source of preanalytical error of potassium determination in the clinical laboratory. Objective: To review the general and recent concepts/mechanisms that underlie the phenomenon of pseudohyperkalemia in contemporary clinical practice. Methods: An up-to-date review of available literature and selected references on the phenomenon of pseudohyperkalemia, its causes, variants, mechanisms, clinical implications, identification, management, and prevention. Conclusion: Pseudohyperkalemia is a fairly common preanalytical error of potassium measurement in the clinical laboratory and a potential cause of misdiagnosis and unnecessary treatment of hyperkalemia. Exclusion of pseudohyperkalemia before the diagnosis of hyperkalemia (true hyperkalemia) is highly recommended.

Primary Hyperoxaluria Screening and Monitoring: Quantitative Measurement of Plasma Oxalate by Gas Chromatography-Mass Spectrometry With High Sensitivity.

Plasma oxalate measurements can be used for the screening and therapeutic monitoring of primary hyperoxaluria. We developed a gas chromatography-mass spectrometry (GC-MS) assay for plasma oxalate measurements with high sensitivity and suitable testing volumes for pediatric populations. Plasma oxalate was extracted, derivatized, and analyzed by GC-MS. We measured the ion at m/z 261.10 to quantify oxalate and the 13C2-oxalate ion (m/z: 263.15) as the internal standard. Method validation included determination of the linear range, limit of blank, limit of detection, lower limit of quantification, precision, recovery, carryover, interference, and dilution effect. The cut-off value between primary and non-primary hyperoxaluria in a pediatric population was analyzed. The detection limit was 0.78 μmol/L, and the linear range was up to 80.0 μmol/L. The between-day precision was 5.7% at 41.3 μmol/L and 13.1% at 1.6 μmol/L. The carryover was <0.2%. The recovery rate ranged from 90% to 110%. Interference analysis showed that Hb did not interfere with plasma oxalate quantification, whereas intralipids and bilirubin caused false elevation of oxalate concentrations. A cut-off of 13.9 μmol/L showed 63% specificity and 77% sensitivity, whereas a cut-off of 4.15 μmol/L showed 100% specificity and 20% sensitivity. The minimum required sample volume was 250 μL. The detected oxalate concentrations showed interference from instrument conditioning, sample preparation procedures, medications, and various clinical conditions. GC-MS is a sensitive assay for quantifying plasma oxalate and is suitable for pediatric patients. Plasma oxalate concentrations should be interpreted in a clinical context.

SAT129 Clinical Conundrum Of Suspected Pancreatitis Masking Diabetic Ketoacidosis

Abstract Disclosure: A. Sood: None. O. Syed: None. A. Sood: None. P. Patel: None. M.M. Alosiyus: None. ​​Abstract: Patients with End-Stage-Renal-Disease (ESRD) have poor renal excretion which can cause false elevation in pancreatic enzymes. We present a case of a pregnant woman on hemodialysis (HD) with elevated lipase levels concerning for acute pancreatitis. Case Presentation: A 25-year-old African American female with history of type 1 diabetes mellitus, ESRD secondary to diabetic nephropathy, diabetic gastroparesis, hypertension presented to the hospital with diffuse severe abdominal pain following HD. Lab showed Anion gap 15, Glucose 304 mg/dL, Creatinine 4.6 mg/dL, Triglyceride 130 mg/dL, Lipase 390 mg/dL, with urine negative for ketones. The abdominal US was negative for gallstones, and revealed a normal size common bile duct. CT scan was deferred due to a positive urine pregnancy test. She was started on IV fluids for suspected pancreatitis. Patient had worsening blood glucose levels as well as anion gap despite being on Humalog and correctional scale insulin. Patient was started on an insulin drip with resolution of the anion gap. Discussion: Patient met 2 of 3 criteria for pancreatitis, with CT and MRI deferred in this case due to pregnancy and low suspicion secondary to negative US result.[5] Pancreatic enzymes can be falsely elevated in ESRD patients. Lipase can be elevated in HD[3] patients due to the lipolytic effect of heparin used during dialysis, while elevation of lipase in DKA remains unclear[2]. Acidosis is common in ESRD patients, thus masking the diagnosis of DKA which also presents with abdominal pain, nausea, vomiting, which can potentially cause a delay in the treatment. The mimicking and masking of these conditions by each other can thereby result in a diagnostic dilemma, which is why a prompt diagnosis of pancreatitis should be made in a patient presenting with DKA. Conclusion: Elevated levels of amylase and lipase are concerning for pancreatitis, however, metabolic processes could also be masked by underlying chronic diseases. While fluid resuscitation is the mainstay treatment for DKA and pancreatitis, it is extremely important to be cautious when a patient has an underlying ESRD. The diagnostic dilemma due to the overlapping diagnosis should be taken into consideration early during the hospitalization, and a high index of clinical suspicion can prevent the unnecessary delay in the treatment.

SAT482 A Case of Falsely Elevated Free T4 and Free T3 Levels Caused by Human Anti Mouse Antibodies.

Abstract Disclosure: I.J. Romao: None. M.H. Shanik: None. Introduction: When there are clinical and biochemical discrepancies with thyroid function tests immunoassay interference should be considered (1). Human anti mouse antibodies (HAMA) are antibodies found in humans that react with immunoglobulins in mice and are used as diagnostic reagents for laboratory measurements. The presence of HAMA most commonly causes a false elevation of thyroid stimulating hormone but can also increase Free T4 and Free T3 levels. Case presentation: A 31 year old woman presented for evaluation of elevated Free T4 and Free T3 levels. For several weeks she complained of feeling neck soreness and palpitations. She had a recent infection and low-grade fever. She also felt pressure behind her eyes. She had a history of anxiety and took Xanax as needed, multivitamin and probiotic. Cousin had thyroid disease. On exam her blood pressure was 138/86, heart rate 80, respiratory rate 12, weight 149 lbs., height 5’5”. Her thyroid was firm and not tender. She had a thyroid ultrasound that showed a homogenous gland with no discrete nodules. TSH was 1.3 uIU/mL (0.27-4.2), Total T4 10.4 ug/dL (4.5 – 12), Free T4 4.6 ng/dL (0.9-1.7), Total T3 1.6 ng/mL (0.8-2.0), Free T3 10.1 pg/mL (2.0-4.4). C reactive protein, erythrocyte sedimentation and interleukin 6 levels were in the normal range. Thyroid peroxidase antibodies and thyroglobulin antibodies were elevated. The differential diagnosis included thyroiditis, pituitary tumor producing thyroid stimulating hormone and thyroid hormone resistance. She did not have a thyroid uptake and scan because she had small children at home. To rule out a pituitary adenoma she had a pituitary MRI that showed a normal small pituitary gland. The test for resistance to thyroid hormone mutation analysis was negative. Over a few months she had some clinical improvement, and her thyroid function tests remained the same which would not be consistent with thyroiditis. HAMA level was checked to evaluate for immunoassay interference with thyroid function tests. The HAMA level was elevated at greater than 600 ng/mL (0-188). Free T4 by equilibrium dialysis was normal at 1.6 ng/dL (1.1 – 2.4). Conclusion: HAMA can cause falsely elevated Free T4 and Free T3 levels. It is important to suspect immunoassay interference when there are inconsistencies in the clinical presentation and thyroid function tests. Identifying the presence of elevated HAMA can prevent misdiagnosis and inappropriate patient management. 1. Favresse J, Burlacu MC, Maiter D, Gruson D. Interferences with thyroid immunoassays: Clinical implications and detection algorithm. Endocrine Reviews. 2018. Pages 830-850. Presentation Date: Saturday, June 17, 2023

A-002 The Prevalence of the High Sensitivity Cardiac Troponin I Outlier and False Positivity Rates on Beckman Coulter Access DxI

Abstract Background The false positive elevation in high sensitivity cardiac troponin I (hsTnI) can be triggered by many factors, for example, fibrin clots, heterophile antibodies, or other sources of troponin interferences. These interferences lead to inaccurate hsTnI results. These inaccurate results described in the literature as the “outliers”. Published studies use statistical tools to identify the outliers based on the discrepancies between the two repeat values. Depending on the instrument platform and the study design, the outlier rate for the conventional troponin I assay was reported from 0.44% to 1.01% (1, 2). In our laboratory, the false positivity rate for the conventional troponin assay on Beckman Coulter DxI platform was determined as 1% (unpublished data). This study aim was to determine both the statistically and clinically significant outliers for hsTnI assay on the Beckman Coulter Access DxI instrument in the academic medical center clinical laboratory setting. Methods A unique test repeat protocol was created. Two parallel hsTnI measurements are conducted in lithium heparin tubes (BD Vacutainer) on Beckman Coulter DXI 800 systems. When the difference between the two results is greater than 30%, a third repeat is automatically ordered and run after additional centrifugation at a higher relative centrifugal force. The outlier determination is based on assessing the difference between the first two values using previously described statistical analysis tools (1). The clinically significant outlier was determined by counting positive results in the first two runs which are not unconfirmed by the third run, i.e., false positive results. Gender specific cutoffs, 14 ng/L for female and 19 ng/L for male, were applied to identify the positive results. Overall, 2935 patients’ results were evaluated during the study. Results Based on the analysis of the first two repeat runs, out of 2935 samples 16 samples, or 0.54%, were identified as the statistical outliers. 2 out of these 16 outliers, or 12.5%, were negative results. Taking into consideration the third repeat data, 13 out of 2935 samples, or 0.44%, were identified as false positive results. Only 9 out of 13 false positive results, or 69.2%, were identified using the statistical approach above. Conclusion The false positivity rate of hsTnI testing has dropped significantly from 1% to 0.44% in a setting of our laboratory. Our refined repeat protocol approach significantly increases the clinician’s confidences in the hsTnI results by capturing potential false positive results. This approach addresses the outliers at an additional expense like reagents, instrument wear and tear, and labor. Therefore, a more robust methodology is still desired by the industry.

Xpert Bladder Cancer Monitor for the Early Detection of Non-Muscle Invasive Bladder Cancer Recurrences: Could Cystoscopy Be Substituted?

XBM was prospectively assessed in spontaneous urine collected just before flexible cystoscopy and washing cytology carried out within the first 2 years follow-up of 337 patients with NMIBC. Recurrences were pathologically confirmed in 49 patients (14.5%), 22 of them being high-risk (6.5%). The XBM sensitivity for detecting any type of recurrence was 69.4% and 63.6% in the cases of high-risk NMIBC. Negative predictive value (NPV) for XBM was 93% for all recurrences and 96.2% for high-risk recurrences. XBM could have avoided 213 invasive controls but missed the detection of 15 recurrences (30.6%)-8 of them of high-risk (36.4%). XBM false positive elevations were detected in 90 patients (26.7%), whereas 10 patients with the invasive method had a false positive result (3%), p <0.001. However, early detection of recurrences during the first year's follow-up after an XBM false positive result was observed in 18 patients (20%). On the other hand, 19 recurrences were detected during this period among the rest of the patients (7.7%)-p = 0.003, and odds ratio (OR) 3.0 (95% CI 1.5-6.0). Regarding one-year follow-up recurrences, 10% were high-risk recurrences in the XBM false positive group and 3.2% in the rest of the patients-p = 0.021, and OR 3.3 (95% CI 1.2-8.9). Additionally, 11.3% of the patients without false positive results developed a recurrence, p = 0.897, for any recurrence, being 10% and 5.2%, respectively, and high-risk and low-risk recurrences, p = 0.506. After searching for the best XBM cutoff for detecting the 38 high-risk initial recurrences and the early high-risk recurrences after a one-year follow-up, a linear discriminant analysis (LDA) of 0.13 could have avoided 11.3% of cystoscopies and bladder wash cytologies, as this cutoff missed only 1 high-risk recurrence (2.6%). More extensive and well-designed studies will confirm if XBM can improve the surveillance of NMIBC.

Assay interference as a cause of false positive troponin T elevation in emergency department patients

BackgroundTroponin assays are used in the diagnosis of myocardial injury and may show elevated results for a variety of reasons. However it is increasingly recognised that cardiac troponin elevation may in some cases be due to assay interference. This is of significant importance as a misdiagnosis of myocardial injury may lead to unnecessary and potentially harmful investigation and treatment for patients. We sought to confirm the accuracy of cardiac high sensitivity troponin T (chsTnT) elevation in an unselected group of patients presenting to the emergency department, by using a second confirmatory cardiac high sensitivity troponin I (chsTnI) assay. MethodsWe identified patients presenting to two local emergency departments over a five-day period who had chsTnT levels measured as part of routine clinical care. All samples with elevated chsTnT levels (above the 99% centile URL) were retested for chsTnI in order to confirm true myocardial injury. ResultsA total of 74 samples from 54 patients were analysed for chsTnT and chsTnI. 7 samples (9.5%) had chsTnI levels < 5 ng/L suggesting assay interference as the cause of chsTnT elevation. ConclusionsAssay interference leading to false positive troponin elevation may be more common than many physicians appreciate and can potentially lead to harmful investigation and treatment for patients. In cases where the diagnosis of myocardial injury is uncertain, a second alternative troponin assay should be performed to confirm true myocardial injury.

False ST-segment elevation by artifact due to an infusion pump.

A patient admitted for non-ST-elevation acute coronary syndrome showed an episode of ST-segment elevation on the monitor. These alterations were due to an artifact produced by the administration of a saline bolus through an infusion pump that disappeared at the end of the bolus. Our findings highlight that the interpretation of the electrocardiogram requires careful analysis and correlation with the clinical situation and with other physiological parameters.

P-136 Increased healthcare costs due to diagnostic imaging services following false elevation of plasma chromogranin A and 24-hour urinary 5-hydroxyindoleacetic acid: A quality improvement project

P-136 Increased healthcare costs due to diagnostic imaging services following false elevation of plasma chromogranin A and 24-hour urinary 5-hydroxyindoleacetic acid: A quality improvement project