Assay-specific Reference Intervals Research Articles

Adult reference intervals for ceruloplasmin by Siemens BN II Nephelometer by Bhattacharya analysis

Background: Low ceruloplasmin may indicate Wilson’s disease or copper deficiency. Ceruloplasmin assays are not well harmonised, necessitating assay specific reference intervals (RI). The lower reference limit (LRL) in the Siemens BN II package insert (0.2 g/L) if reported to two significant figures was previously shown to be too high in Asian cities. However, studies from predominantly Caucasian populations were lacking.

Reference Intervals in Coagulation Analysis.

Blood coagulation analysis is characterized by the application of a variety of materials, reagents, and analyzers for the determination of the same parameter, or analyte, by different laboratories worldwide. Accordingly, the application of common reference intervals, that, by definition, would represent a "range of values (of a certain analyte) that is deemed normal for a physiological measurement in healthy persons," is difficult to implement without harmonization of procedures. In fact, assay-specific reference intervals are usually established to allow for the discrimination of normal and abnormal values during evaluation of patient results. While such assay-specific reference intervals are often determined by assay manufacturers and subsequently adopted by customer laboratories, verification of transferred values is still mandatory to confirm applicability on site. The same is true for reference intervals that have been adopted from other laboratories, published information, or determined by indirect data mining approaches. In case transferable reference intervals are not available for a specific assay, a direct recruiting approach may or needs to be applied. In comparison to transferred reference interval verification, however, the direct recruiting approach requires a significantly higher number of well-defined samples to be collected and analyzed. In the present review, we aim to give an overview on the above-mentioned aspects and procedures, also with respect to relevant standards, regulations, guidelines, but also challenges for both, assay manufacturers and coagulation laboratories.

The establishment of LC-MS/MS assays-specific reference intervals for serum folates and its application in evaluating FA-supplemented folate deficiency patients: Appeals for a suitable and individualized supplementation

BackgroundLittle known about folates status in folate deficiency patients. This study aims to establish liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay-specific reference intervals (RIs) for serum 5-Methyltetrahydrofolate (5MeTHF), folic acid (FA), 5-Formyltetrahydrofolate (5FoTHF), and total folate (TFOL), and investigate the folates status in FA-supplemented folate deficient patients. MethodsSera from 120 reference subjects were selected and measured. An LC-MS/MS method for serum 5MeTHF, FA, and 5FoTHF was employed. RIs were derived based on the CLSI C28-A3. Serum folate levels of 38 FA-supplemented folate deficiency patients were analyzed. ResultsRIs (median) for 5MeTHF, FA, 5FoTHF, and TFOL were 3.83–62.33 nmol/L (12.27 nmol/L), 0.30–0.92 nmol/L (0.49 nmol/L), <0.73 nmol/L (0.00 nmol/L), and 4.17–63.47 nmol/L (12.66 nmol/L), respectively. Approximately 53 % (20/38), 74 % (28/38), and 63 % (24/38) of patients presented high levels of 5MeTHF, FA, and TFOL, respectively, which far exceeded the upper reference limit (URL) of the corresponding RIs. A half (18/38) of patients showed simultaneously higher 5MeTHF and FA levels which were beyond the URLs of RIs. Near one-third (11/38) of patients exhibited extremely high FA levels which exceeded the 100-fold URL of RIs. The highest levels can be 539 nmol/L for FA, 364 nmol/L for 5MeTHF, and 686 nmol/L for TFOL. ConclusionsLC-MS/MS assay-specific RIs were established for folates vitamers without age or gender partitioning. Abnormally high levels of unmetabolized FA and 5MeTHF were observed in quite a few FA-supplemented patients. Considering the adverse risks caused by folates excess, we appeal for a justifiable and individualized FA supplementation. We also recommend establishing LC-MS/MS assay-specific RIs for routine monitoring of folates status.

The Diagnosis of Normocalcaemic Hyperparathyroidism is Strikingly Dissimilar Using Different Commercial Laboratory Assays.

We assessed the impact of intact parathyroid hormone (iPTH) and adjusted calcium analyses on Abbott, Roche and Siemens analytical platforms in the diagnosis of normocalcaemic primary hyperparathyroidism (NCPHPT). These assays are used by over 85% of clinical laboratories in the UK. Over five months, consecutive serum samples from outpatients with NCPHPT in the laboratory with Abbott assays were identified, aliquoted and stored at -80°C. Frozen aliquots were transported monthly to the other two laboratories. After thawing, samples were mixed and analysed immediately for calcium, albumin and iPTH in the laboratories with Abbott, Roche and Siemens analytical platforms. Adjusted calcium was calculated using the equation used in the respective laboratory. Diagnostic concordance of iPTH and adjusted calcium were assessed using manufacturer-provided assay-specific reference intervals and the pathology harmony reference interval respectively. Fifty-five patients with NCPHPT were identified using Abbott assays. Of these, 16 (29.1%) and 11 (20.0%) had NCPHPT, 9 (16.4%) and 13 (23.6%) had hypercalcaemic primary hyperparathyroidism, and 30 (54.6%) and 31 (56.4%) patients had normal results when analysed in laboratories with Roche and Siemens assays, respectively. The diagnosis of NCPHPT was strikingly different depending on the commercial assay used. There is a pressing need for iPTH assay harmonisation and robust reference intervals. Reference intervals may become invalid if an assay drifts, as exemplified by adjusted calcium in this study.

Sclerostin: From Molecule to Clinical Biomarker.

Sclerostin, a glycoprotein encoded by the SOST gene, is mainly produced by mature osteocytes and is a critical regulator of bone formation through its inhibitory effect on Wnt signaling. Osteocytes are differentiated osteoblasts that form a vast and highly complex communication network and orchestrate osteogenesis in response to both mechanical and hormonal cues. The three most commonly described pathways of SOST gene regulation are mechanotransduction, Wnt/β-catenin, and steroid signaling. Downregulation of SOST and thereby upregulation of local Wnt signaling is required for the osteogenic response to mechanical loading. This review covers recent findings concerning the identification of SOST, in vitro regulation of SOST gene expression, structural and functional properties of sclerostin, pathophysiology, biological variability, and recent assay developments for measuring circulating sclerostin. The three-dimensional structure of human sclerostin was generated with the AlphaFold Protein Structure Database applying a novel deep learning algorithm based on the amino acid sequence. The functional properties of the 3-loop conformation within the tertiary structure of sclerostin and molecular interaction with low-density lipoprotein receptor-related protein 6 (LRP6) are also reviewed. Second-generation immunoassays for intact/biointact sclerostin have recently been developed, which might overcome some of the reported methodological obstacles. Sclerostin assay standardization would be a long-term objective to overcome some of the problems with assay discrepancies. Besides the use of age- and sex-specific reference intervals for sclerostin, it is also pivotal to use assay-specific reference intervals since available immunoassays vary widely in their methodological characteristics.

Clinical concordance assessment should be an integral component of laboratory method comparison studies: A regression transference of routine clinical data approach

Manufacturer-provided assay-specific reference intervals may not compensate for between assay differences leading to method related clinical discordance. Not all laboratories, however, assess clinical concordance as part of method comparison studies. We assessed the utility of method comparison data combined with routine clinical data to assess method related clinical concordance in the diagnosis and management of subclinical hypothyroidism (SCH).Passing-Bablok method comparison regression analysis was performed for both thyroid stimulating hormone (TSH) and free thyroxine (fT4) from 100 samples analysed by Abbott and Roche methods. Primary care samples indicative of SCH were identified from the laboratory information system (LIMS) of two laboratories (one with Roche methods and one with Abbott) over four months. For Roche and Abbott TSH and fT4 results, the Passing-Bablok regression equations were used to predict Abbott and Roche results respectively. The predicted results were interpreted using manufacturer-provided assay-specific reference intervals and compared to those of the previous SCH sample exchange study.On laboratory method comparison, Roche TSH and fT4 results were 30 ± 13% and 16 ± 7% higher compared to Abbott assays respectively. Of those with results indicative of SCH by Roche assays, 76.8% would have had normal thyroid function using predicted Abbott assay results and 46.9% of those with results indicative of SCH by Abbott assays would have had a biochemical indication for levothyroxine replacement using predicted Roche assay results. The results from the regression-based approach were comparable to the previous SCH sample exchange study.A regression-based approach using routine method comparison data and real-world clinical data identifies potential clinical discordance. We suggest that clinical concordance assessment be an integral component of laboratory method comparison studies.

Distribution of HOMA-IR in a population-based cohort and proposal for reference intervals.

Insulin resistance (IR) is a hallmark of type 2 diabetes mellitus (DM). The homeostatic model assessment of insulin resistance (HOMA-IR) provides an estimate for IR from fasting glucose and insulin serum concentrations. The aim of this study was to obtain a reference interval for HOMA-IR for a specific insulin immunoassay. The Gutenberg Health Study (GHS) is a population-based, prospective, single-center cohort study in Germany with 15,030 participants aged 35-74years. Fasting glucose, insulin, and C-peptide were available in 10,340 participants. HOMA-IR was calculated in this group and three reference subgroups with increasingly more stringent inclusion criteria. Age- and sex-dependent distributions of HOMA-IR and reference intervals were obtained. In a substudy three insulin assays were compared and HOMA-IR estimated for each assay. Among the 10,340 participants analyzed there were 6,590 non-diabetic, 2,901 prediabetic, and 849 diabetic individuals. Median (interquartile range [IQR]) HOMA-IR was 1.54 (1.13/2.19), 2.00 (1.39/2.99), and 4.00 (2.52/6.51), respectively. The most stringently selected reference group consisted of 1,065 persons. Median (IQR) HOMA-IR was 1.09 (0.85/1.42) with no significant difference between men and women. The 97.5th percentile was 2.35. There was a non-significant trend towards higher values with older age. Comparison of three immunoassays for insulin showed an unsatisfactory correlation among the assays and systematic differences in calculated HOMA-IR. We present HOMA-IR reference intervals for adults derived by more or less stringent selection criteria for the reference cohort. In addition we show that assay specific reference intervals for HOMA-IR are required.

Pediatric reference intervals for endocrine markers and fertility hormones in healthy children and adolescents on the Siemens Healthineers Atellica immunoassay system.

Rapid development in childhood and adolescence combined with lack of immunoassay standardization necessitates the establishment of age-, sex-, and assay-specific reference intervals for immunochemical markers. This study established reference intervals for 11 immunoassays on the new Siemens Healthineers Atellica® IM Analyzer in the healthy CALIPER cohort. A total of 600 healthy participants (birth to 18 years) were recruited from the community, and serum samples were collected with informed consent. After sample analysis, age- and sex-specific differences were assessed, and outliers were removed. Reference intervals were established using the robust method (40-<120 participants) or nonparametric method (≥120 participants). Of the 11 immunoassays studied, nine required age partitioning (i.e.,dehydroepiandrosterone-sulfate, estradiol, ferritin, folate, follicle-stimulating hormone, luteinizing hormone, progesterone, testosterone, vitamin B12), and seven required sex partitioning. Free thyroxine and thyroid-stimulating hormone demonstrated no significant age- and/or sex-specific differences. Overall, the age- and sex-specific trends observed closely mirrored those previously reported by CALIPER on other platforms as well as other internationally recognized studies. However, established lower and upper limits demonstrated some discrepancies between published values from healthy cohorts on alternate analytical systems, highlighting differences between manufacturers and the need for platform-specific reference intervals for informed pediatric clinical decision-making.

CDC Clinical Standardization Programs (CSP) for Free Thyroxine (FT4) to Improve the Accuracy and Reliability of FT4 Measurements in Patient Care and Clinical Research

Reliable FT4 measurement is critical to assess thyroid function and diagnose and treat thyroid disorders. The Partnership for the Accurate Testing of Hormones (PATH) categorizes FT4 as a biomarker in high need for standardization, and currently high inter-assay variability restricts the interpretation of FT4 results in patient care to assay-specific reference intervals. The CDC CSP has partnered with the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and PATH to create a standardization program for FT4 to improve accuracy, reliability, and comparability of current methods and thus to improve diagnosis, treatment and prevention of thyroidal illnesses. Currently, there are no serum FT4 reference materials available to assess the accuracy and reliability of FT4 assays. CDC has developed an accurate and sensitive reference measurement procedure (RMP) to create commutable serum reference materials with FT4 target values. Assay manufacturers, research and clinical laboratories can use these reference materials to assess their calibration, certify the analytical performance of their measurements, and monitor performance over time by collaborating with CDC CSP. The CDC FT4 RMP uses equilibrium dialysis (ED) with LC-MS/MS based on an internationally recognized ED procedure[1] followed by solid-phase and solvent extractions. Certified primary reference material IRMM468 was used to prepare calibrators. Chromatographic separation is achieved with a gradient of methanol and water with 0.1% formic acid. FT4 is quantified using positive electrospray ionization in positive mode. The intra- and inter-day imprecision of the CDC RMP are 3.0% and 1.1%. A comparison among FT4 RMPs resulted in a +2.5% bias for the CDC RMP to the mean for all labs. The CDC RMP measurement range was 3.02-258 pmol/L and thus suitable for analysis of hypo- and hyperthyroid patients. The CDC FT4 RMP demonstrates good accuracy and precision, and can be used as a viable accuracy base to which routine methods can be compared. An initial comparison study of a commercially available FT4 immunoassay (IA) and the CDC RMP with 24 samples (7.98-109 pmol/L) indicated a mean bias of -37.7%, further indicating a need for standardization. Findings from an IFCC study suggest that alignment of IA measurements to a FT4 RMP can improve comparability and would allow for a uniform reference interval for FT4.[2] CDC CSP established a new standardization program for FT4 to address the needs of the community and assist with improving test comparability and reliability.1. Clin. Chem. Lab. Med. 2011, 49: 1275-81. 2. Clin. Chem. 2017, 63: 1642-52.

Determination of a Beckman Coulter AU turbidometric method-specific caeruloplasmin reference interval.

Method-dependent variation of caeruloplasmin measurement is significant and necessitates the requirement for assay-specific reference intervals. Local determination becomes necessary in the absence of suitable published or manufacturer-quoted reference intervals. Applicability of the Beckman Coulter AU-quoted reference interval was determined by assay of 20 surplus serum samples from patients attending the medical renal stones clinic at University Hospital Southampton. Subsequently, 60 additional samples were collected for local reference interval determination. Samples were analysed for caeruloplasmin using the Beckman Coulter AU turbidometric kit on an AU680 analyser. Outliers were removed, and non-parametric rank analysis of the results was performed. The Beckman Coulter-quoted reference interval of 200-600 mg/L was unsuitable with 40% of the verification samples falling below 200 mg/L. A caeruloplasmin reference interval of 150-320 mg/L was established. Users should be aware the quoted Beckman Coulter AU turbidometric reference interval may not be appropriate. We have established a method-specific adult reference interval for routine use.

IgG subclasses quantitation: Analytical performance of The Binding Site SPAPLUS® human assay and comparison with Siemens BNII® assay

ObjectivesAccurate evaluation of analyzers is highly recommended before these devices are broadly introduced for routine testing. Concerning quantification of IgG subclasses (IgGSc), standardization has not yet been reached and thus different assays might lead to different results. Here we report the analytical performances of The Binding Site (TBS) SPAPLUS® human IgGSc assay and the concordance with the Siemens BNII® human IgGSc assay. Design and methodsWe evaluated precision, LoB, LoD and linearity of TBS SPAPLUS® human IgGSc immunoassay. Quantitation of IgGSc in 53 patients' serum samples was performed in parallel on both analyzers. Results from both assays were compared. ResultsAnalytical performances of the TBS SPAPLUS® human IgGSc assay are acceptable for routine clinical use. According to the method comparison study, TBS assay measures lower values than Siemens assay for IgG1 and IgG4, whereas for IgG2 and IgG3 TBS provides greater values. All assays present a proportional bias, greater in the case of IgG3 and IgG4 assays. Individual subclass agreement, based on the classification of samples within three categories (low, normal and high) according to assay-specific reference intervals, range from 75% (IgG1) to 92% (IgG2). However, total classification agreement over all four subclasses only account for 55% of samples. ConclusionResults obtained from both assays are not interchangeable. Standardization of IgGSc assay and review of the reference ranges must be accomplished in order to achieve a higher degree of agreement between different methods.

Reference intervals and longitudinal changes in copeptin and MR-proADM concentrations during pregnancy.

Vasopressin and adrenomedullin and their stable by-products copeptin and midregional part of proadrenomedullin (MR-proADM) are promising biomarkers for the development of preeclampsia. However, clinical use is hampered by the lack of trimester-specific reference intervals. We therefore estimated reference intervals for copeptin and MR-proADM in disease-free Dutch women throughout pregnancy. Apparently healthy low risk pregnant women were recruited. Exclusion criteria included current or past history of endocrine disease, multiple pregnancy, use of medication known to influence thyroid function and current pregnancy as a result of hormonal stimulation. Women who miscarried, developed hyperemesis gravidarum, hypertension, pre-eclampsia, hemolysis elevated liver enzymes and low platelets, diabetes or other disease, delivered prematurely or had a small for gestational age neonate were excluded from analyses. Blood samples were collected at 9-13 weeks (n=98), 27-29 weeks (n=94) and 36-39 weeks (n=91) of gestation and at 4-13 weeks post-partum (PP) (n=89). Sixty-two women had complete data during pregnancy and PP. All analyses were performed on a Kryptor compact plus. Copeptin increases during pregnancy, but 97.5th percentiles remain below the non-pregnant upper reference limit (URL) provided by the manufacturer. MR-proADM concentrations increase as well during pregnancy. In trimesters 2 and 3 the 97.5th percentiles are over three times the non-pregnant URL provided by the manufacturer. Trimester- and assay-specific reference intervals for copeptin and MR-proADM should be used. In addition, consecutive measurements and the time frame between measurements should be considered as the differences seen with or in advance of preeclampsia can be expected to be relatively small compared to the reference intervals.

Similar but not consistent: Revisiting the pitfalls of measuring IgG subclasses with different assays.

Laboratory quantification of IgG subclasses (IgGSc) is a well-established second-line tool for differential diagnosis of immune deficiencies. However, so far there is still no internationally approved standard available for IgGSc, and different assays are prone to produce divergent results. In this study, we evaluated the comparability and equivalence of two commercially available IgGSc assays, one being the Siemens IgGSc assay on a BN ProSpec analyzer and the other being The Binding Site (TBS) IgGSc assay on a Roche cobas c502 analyzer. We analyzed a total of 50 patient plasma samples obtained over a 3-month period with both IgGSc assays and compared the resulting data based and the CLSI EP09-A3 method comparison guideline. Depending on the analyzed IgGSc type, the average relative differences in IgGSc concentration (g/L) between the two assays were considerable, starting with -13.5% for IgG1 and 11.3% for IgG2, over -47.3% for IgG4, and up to 52.9% for IgG3. Applying the assay-specific reference intervals, the classification agreement (below, within, or above the reference range) ranged from 88% to 90% for the individual subclasses. However, only 68% of samples showed an overall classification agreement. The comparability of the two IgGSc assays proved to be limited and might be considered similar at best on the diagnostic level. Laboratory specialists as well as clinicians therefore should be cautious when using and interpreting IgGSc measurements obtained with different assays or analyzers.

Impacto del empleo de umbrales específicos de referencia en el diagnóstico de las alteraciones funcionales tiroideas en la mujer gestante

ObjectiveTo determine trimester- and assay-specific reference intervals for thyroid hormones during pregnancy, and the impact of using non-specific intervals on the diagnosis of functional disorders in the first trimester. MethodsA total of 759 healthy pregnant women older than 18 years with uncomplicated single intrauterine gestations and attending Primary Care Centres were consecutively recruited from January 2014 to September 2014. After excluding women who did not complete the follow-up during pregnancy, and those with functional thyroid disorders or with thyroid-specific autoantibodies, a total of 411 pregnant women were selected as the reference population. TSH, FT4, and FT3 were measured in each trimester using electrochemiluminescence immunoassay, and urinary iodine concentration was measured in the first and in the third trimester using high performance liquid chromatography. ResultsThe TSH reference intervals expressed as median and 2.5-97.5 percentiles were: 1.53μIU/ml (0.26-3.95), 1.90μIU/ml (0.78-3.85) and 1.89μIU/ml (0.71-3.61) in first, second and third trimesters, respectively. The median urinary iodine concentration (UIC) was 171.31μg/l (90.7-274.9) in the first trimester and 190.37μg/l (96.44-360.38) in the third. Interpretation of thyroid function tests using non-local-pregnant reference intervals would result in misclassification of the thyroid function in a significant percentage of pregnant women (19.8% with the proposed international specific reference intervals, and 8.52% with the non-specific reference intervals of our assay). ConclusionsThe use of non-local reference intervals for the diagnosis of thyroid disorders during pregnancy could lead to a large number of misclassified results, contributing to sub-optimal patient care.

Validation of the Accutrend Plus point-of-care triglyceride analyzer in horses, ponies, and donkeys.

To assess the accuracy and reliability of a point-of-care (POC) triglyceride analyzer and to establish reference intervals for blood ([TRIG]POC/WB ) and plasma triglyceride concentrations ([TRIG]POC/PL ) in horses, ponies, and donkeys. Prospective study. University teaching hospital. 120 adult healthy equids (78 horses and ponies, 42 donkeys) and 79 equids suffering from hypertriglyceridemia (73 horses and ponies, 6 donkeys). None. [TRIG]POC/WB and [TRIG]POC/PL were measured using a POC analyzer and plasma triglyceride concentrations were measured using a standard laboratory assay ([TRIG]LAB/PL ). Reference intervals were determined. Test accuracy was assessed by Bland-Altman comparison of POC measurements with standard laboratory measurements and by evaluating linearity of dilutional series. Test reliability was assessed by repeated serial measurements. [TRIG]POC/WB and [TRIG]POC/PL were below the analytic range of the POC assay (<0.8 mmol/L [<70 mg/dL]) in healthy horses and ponies, whereas the reference intervals were 0.82-3.14 mmol/L (73-278 mg/dL) and 0.87-3.02 mmol/L (77-267 mg/dL), respectively, in donkeys. The POC analyzer systematically overestimated triglyceride concentrations when compared to a standard laboratory assay. The difference between [TRIG]POC/WB and [TRIG]POC/PL was small and clinically negligible. The coefficient of variation of repeated measures performed on the POC analyzer was below 10% for [TRIG]POC/WB and [TRIG]POC/PL , both in horses and donkeys and at all concentration ranges. The POC analyzer allows accurate and reliable measurement of [TRIG]POC/WB and [TRIG]POC/PL in horses, ponies, and donkeys in clinical settings. Assay-specific reference intervals should be determined for diagnosis and clinical monitoring of hypertriglyceridemia in equids.

Thyroid function in pregnancy: what is normal?

Gestational thyroid dysfunction is common and associated with maternal and child morbidity and mortality. During pregnancy, profound changes in thyroid physiology occur, resulting in different thyroid-stimulating hormone (TSH) and free thyroxine (FT4) reference intervals compared to the nonpregnant state. Therefore, international guidelines recommend calculating trimester- and assay-specific reference intervals per center. If these reference intervals are unavailable, TSH reference intervals of 0.1-2.5 mU/L for the first trimester and 0.2-3.0 mU/L for the second trimester are recommended. In daily practice, most institutions do not calculate institution-specific reference intervals but rely on these fixed reference intervals for the diagnosis and treatment of thyroid disorders during pregnancy. However, the calculated reference intervals for several additional pregnancy cohorts have been published in the last few years and show substantial variation. We provide a detailed overview of the available studies on thyroid function reference intervals during pregnancy, different factors that contribute to these reference intervals, and the maternal and child complications associated with only minor variations in thyroid function. There are large differences in thyroid function reference intervals between different populations of pregnant women. These differences can be explained by variations in assays as well as population-specific factors, such as ethnicity and body mass index. The importance of using correct reference intervals is underlined by the fact that even small subclinical variations in thyroid function have been associated with detrimental pregnancy outcomes, including low birth weight and pregnancy loss. It is therefore crucial that institutions do not rely on fixed universal cutoff concentrations, but calculate their own pregnancy-specific reference intervals.

Establishment of trimester-specific reference intervals for thyroid hormones in Korean pregnant women.

BackgroundEstablishment of trimester- and assay-specific reference intervals for every population is recommended. The aim of this study was to establish a trimester- and assay-specific reference interval for thyroid-stimulating hormone (TSH) and free thyroxine (FT4) in Korean pregnant women.MethodsFrom April 2012 to December 2012, 531 pregnant women receiving prenatal care and 238 age-matched, non-pregnant women were enrolled in this study. After excluding patients with pregnancy-associated complications or thyroid-specific autoantibody, 465 pregnant and 206 non-pregnant women were included. Non-parametric analysis (2.5-97.5th percentile) was performed to determine the reference interval. Levels of TSH and FT4 were determined by electrochemiluminescence immunoassay (Elecsys thyroid tests, Roche Diagnostics, Germany).ResultsThe TSH reference intervals were 0.01-4.10, 0.01-4.26, and 0.15-4.57 mIU/L for the first, second, and third trimester, respectively. From the first trimester to the third trimester, the median TSH levels showed a significantly increasing trend (P<0.0001). The FT4 reference intervals were 0.83-1.65, 0.71-1.22, and 0.65-1.13 ng/dL for the first, second, and third trimester, respectively, showing a significantly decreasing trend (P<0.0001).ConclusionsEstablishing trimester-specific reference intervals in pregnant women is essential for accurate assessment of thyroid function. Our population-specific and method-specific reference intervals will be useful for screening Korean pregnant women for thyroid disease.

Soluble serum Klotho levels in healthy subjects. Comparison of two different immunoassays

ObjectiveSoluble serum Klotho is a new biomarker linked to chronic kidney disease, cardiovascular disease and diabetes. This study describes the evaluation and comparison of two different immunoassays and establishment of assay specific reference intervals in adults. Design and methodsSerum Klotho concentrations were determined in 120 healthy adults aged 19–66years. Blood samples were collected, and stored sera were assayed for Klotho according to age and gender. In addition several other clinical and laboratory characteristics were determined in the cohort and compared to the levels of serum Klotho. ResultsSerum Klotho levels were significantly higher in time-resolved fluorescence immunoassay (TRF) compared to an ELISA (IBL) and no correlation was found between the assays. No signal was obtained in either assay when the standard curve was switched between the two different immunoassays. The median serum Klotho concentration using TRF was 61ng/mL (2.5–97.5% reference limits; 11–181ng/mL) for males and 99ng/mL (2.5–97.5% reference limits; 19–316ng/mL) for females while the ELISA gave a mean value of 472pg/mL (2.5–97.5% reference limits; 204–741pg/mL) with no difference between genders. Concentrations of serum Klotho were independently associated with estimated glomerular filtration rate (eGFR) and body weight using TRF whereas serum Klotho concentrations were associated with age using the ELISA. ConclusionComparison of two different immunoassays for serum Klotho indicate, that the protein exists in human beings in different forms which may function as independent factors and whose role and potential value as biomarkers needs to be evaluated separately. Reference intervals specific for the different forms recognized by the different assays were calculated in this study.

Point-of-Care Testing of Coagulation and Fibrinolytic Status during Postpartum Haemorrhage: Developing a Thrombelastography®-Guided Transfusion Algorithm

Thrombelastography® is a monitor of coagulation and fibrinolytic status, with point-of-care applications in managing haemorrhaging patients. Advocates have suggested a possible role in managing obstetric haemorrhage. This study aims to develop a pregnancy-specific thrombelastography-guided transfusion algorithm, which could be integrated into the management of postpartum haemorrhage. In this prospective observational study, 57 healthy, term-parturients provided pre-caesarean whole blood specimens for thrombelastography analyses. Specimens were processed according to a standardised protocol involving simultaneous analyses using three assays: native (non-activated); kaolin-activated; and kaolin and tissue factor-activated (RapidTEG®). For each assay, the following thrombelastography parameters were measured: reaction time (minutes); clot formation kinetics time (minutes); maximum amplitude (mm); and a angle (degree). Subsequent reference values were used to establish assay-specific reference intervals. For all thrombelastography parameters studied, reference values obtained using a non-activated assay differed from the corresponding values obtained using activated assays, and also demonstrated greater inter-sample variability. From the assay-specific reference intervals obtained, it was possible to establish a pregnancy-specific thrombelastography-guided transfusion algorithm. Specific features of this transfusion algorithm included the preferential use of activated assays, the need for duplicates and a recommendation that an initial baseline thrombelastography measurement is established for subsequent serial comparisons. This transfusion algorithm has been developed to assist with assessment of coagulation and fibrinolytic status during postpartum haemorrhage.

Reference interval and determinants of the serum homocysteine level in a Korean population

In this study, we estimated the reference intervals of the serum homocysteine (Hcy) level using two automated immunoassays, and we demonstrated the effects of various factors on the Hcy level in a Korean population. We calculated the gender- and assay-specific reference intervals using the data from 809 healthy Koreans, and we assessed the effects of physiologic and lifestyle factors on the Hcy level. The upper limit was higher in males (19.21 and 19.76 μmol/l) than that in females (14.99 μmol/l and 15.16 μmol/l, AxSym and ADVIA centaur, respectively); the upper limits were comparable between the two assays. Smokers, vitamin nonusers, and persons without regular exercise showed a lower folate level and a higher Hcy level. The risk of hyperhomocysteinemia was significantly associated with the male gender (adjusted OR: 5.705, P-value: 0.008) and with the low folate level group (adjusted OR: 10.412, P-value: 0.002) on the multivariate analysis. The Hcy level was significantly different according to various factors, especially in the gender and folate level. The reference interval should be determined for each ethnic population and for each assay. The appropriate cutoff for assessing the risk for cardiovascular disease or stroke should also be validated in each population.