False-positive Specimens Research Articles

Analysis of factors with low positive predictive value in the diagnosis of urinary tract infection by flow cytometry.

Culture-negative urine specimens can be rapidly screened by urine flow cytometry (UFC), while low positive predictive value (PPV) limits the clinical application. We explored the factors associated with a low PPV. A total of 5095 urine specimens were analyzed with UFC and culture. Diagnostic performance of leukocytes, bacteria, and BACT-info flags was evaluated by sensitivity, specificity, PPV, and negative predictive value (NPV). The association of contaminated culture and squamous epithelial cell count and BACT-info flag was performed by logistic regression analysis. The NPVs of parallel combination of bacteria and leucocytes were 98.9% in males and 97.9% in females, and PPVs of serial combination were 86.6% and 77.8% in men and women, respectively. The PPV of Gram-negative flag was higher than that of Gram-positive flag. The proportions of contamination in the urine culture results of false positive specimens were 86.9% in males and 98.5% in females at the cutoff points of the serial combination, and these parameters were 53.2% in males and 85.6% in females for the Gram-positive flag. There was a statistically significant association between contaminated cultures and squamous epithelial cells count in females, but not in males. Associations between contaminated cultures and Gram-positive flags or Gram-pos/-neg flags were statistically significant, but there was no association between contaminated cultures and Gram-negative flags. A serial combination of leukocytes and bacteria may maximize PPV in the diagnosis of bacterial urinary tract infection by urine flow cytometry, and contamination is the main reason for a low PPV.

False-Positive Amphetamines in Urine Drug Screens: A 6-Year Review.

Immunoassays are routinely used to provide rapid urine drug screening results in the clinical setting. These screening tests are prone to false-positive results and ideally require confirmation by mass spectrometry. In this study, we have examined a large number of urine specimens where drugs other than amphetamines may have caused a false-positive amphetamine immunoassay screening result. Urine drug screens (12,250) in a clinical laboratory that used the CEDIA amphetamine/ecstasy method were reviewed for false-positive results over a 6-year period (2015-2020). An additional 3,486 referred samples, for which confirmatory--mass spectrometry was requested, were also reviewed. About 86 in-house samples and 175 referral samples that were CEDIA false-positive screens were further analyzed by an LC-QTOF general unknown screen. Potential cross-reacting drugs were identified, and their molecular similarities to the CEDIA targets were determined. Commercial standards were also analyzed for cross-reactivity in the amphetamine/ecstasy CEDIA screen. Positive amphetamine results in 3.9% of in-house samples and 9.9% of referred tests for confirmatory analysis were false positive for amphetamines. Of these false-positive specimens, on average, 6.8 drugs were detected by the LC-QTOF screen. Several drugs were identified as possible cross-reacting drugs to the CEDIA amphetamine/ecstasy assay. Maximum common substructure scores for 70 potential cross-reacting compounds were calculated. This was not helpful in identifying cross-reacting drugs. False-positive amphetamine screens make up to 3.9-9.9% of positive amphetamine screens in the clinical laboratory. Knowledge of cross-reacting drugs may be helpful when mass spectrometry testing is unavailable.

Clinicopathological study of surgery for pulmonary metastases of hepatoblastoma with indocyanine green fluorescent imaging.

The prognosis of metastatic hepatoblastoma remains poor; to improve it, pulmonary metastasis must be controlled. Indocyanine green (ICG) fluorescent imaging has been used recently for lung metastasectomy. The objective of our study was to clarify the usefulness of ICG imaging for lung metastasectomy of hepatoblastoma using detailed clinicopathological analysis. Patients with hepatoblastoma who underwent resection of pulmonary metastases with ICG fluorescent imaging were studied using a retrospective analysis of clinical information, a review of their surgical records, and a histological analysis of their metastatic nodules. Sixteen patients were enrolled. In total, 61 ICG imaging-guided pulmonary metastasectomies were performed, and 350 ICG-positive and 23 ICG-negative specimens were identified. Tumors were confirmed in 250 of the ICG-positive specimens, including eight nonpalpable nodules, on microscopic examination. ICG-positive and tumor-negative specimens showed histological changes suggesting the regression of a tumor or bloodstream disturbance. Surgical resection is one of the few treatment strategies available to patients with hepatoblastoma with multiple relapses of pulmonary metastasis resistant to chemotherapy. This study demonstrates the high sensitivity of ICG imaging and that thorough metastasectomy can be achieved with ICG imaging. Because a number of false-positive specimens were detected, further optimization of the dose of ICG and the timing of its administration, and establishment of detection of ICG-positive, tumor-negative nodules during surgery are important issues. Several false-negative specimens were also detected, suggesting the presence of ICG-negative metastatic tumors. Palpation during surgery and imaging studies remain essential for detecting metastatic lesions, even in the era of ICG imaging.

Near-Infrared Fluorescence Imaging in the Identification of Parathyroid Glands in Thyroidectomy.

To assess the ability of near-infrared fluorescence imaging (NIFI) to identify parathyroid glands (PGs) among histologically proven PG/non-PG specimens compared with a surgeon's visual acumen, and to determine NIFI sensitivity in detecting incidentally resected PGs from thyroidectomy specimens, compared to the surgeon's visual inspection. Prospective study. With mean age of 61 years, 36 patients with various thyroid diseases were enrolled. Possible PGs (n = 28) and lymph nodes (n = 32) were identified by the experienced surgeon's visual inspection. Using NIFI, 15 PGs were further identified from thyroidectomy specimens. For these 75 specimens, the surgeon's judgments (PG vs. non-PG) were recorded. Histological evaluation was performed after examining the NIFI auto-fluorescence of each specimen. There were no significant differences in sensitivity, specificity, positive predictive value, and negative predictive value between the surgeon's visual inspection and NIFI in identifying PGs, with values of 100%/97.1%, 85.0%/87.5%, 85.4%/87.2%, and 100%/97.2%, respectively. The sensitivity of NIFI (82.9%) for detection of PGs from thyroidectomy specimens was significantly higher than that of the surgeon's visual inspection (61.0%). False negative specimens contained bleeding/congestion and/or encapsulation by thick tissues, whereas false positive specimens contained electrocoagulated tissues. NIFI showed results comparable to the experienced surgeon's visual inspection in identifying PGs. This could benefit novice surgeons. NIFI may be useful for experienced surgeons to locate incidentally resected PGs within thyroidectomy specimens for auto-transplantation. Prevention of intra-gland bleeding and congestion, careful removal of thick capsules, and bloodless surgeries without electrocoagulation are important for reducing false positive and false negative results. Laryngoscope, 131:1188-1193, 2021.

Clinical Application Evaluation of a Fourth-Generation HIV Antigen Antibody Combination Screening Assay.

Human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS) are infectious diseases with high mortality. Early diagnosis is crucial. Combining HIV antibody and p24 antigen, the Elecsys HIV combi PT assay is a fourth generation HIV screening assay. The sensitivity and specificity of this assay was examined. A total of 111,556 samples was conducted from January 1, 2016, to June 30, 2018 in Zhongshan Hospital of Yat-Sen University. We conducted a fourth-generation HIV test of retrospective HIV screening samples and assessed the reliability of using signal-to-cutoff (S/CO) ratios to distinguish false positive HIV antibody reactions and analyzed false positives. A total of 122 specimens were confirmed as HIV-1 infected by western blot (WB) and HIV nucleic acid assays. The median S/CO ratio for HIV false positive specimens was 3.27, while for the HIV-infected specimen it was 391.7. Receiver operating characteristic (ROC) analysis showed that the best diagnostic point for HIV was 22.85 S/CO. The sensitivity, specificity, and Youden index were 100%, 97.8%, and 0.978, respectively. The highest false positive rate of 26.4% was found in patients with malignant tumors and blood diseases. The results of this study show that the fourth-generation Elecsys HIV combination PT test can identify early HIV infected and can be a useful adjunct to help clinicians to manage the disease by viral load testing and starting an appropriate therapy. Our research data provides a reference for subsequent research and HIV testing in the region.

Balance design for robust foliar nutrient diagnosis of \u201cPrata\u201d banana (Musa spp.)

The “Cavendish” and “Prata” subgroups represent respectively 47% and 24% of the world banana production. Compared to world average progressing from 10.6 to 20.6 t ha−1 between 1961 and 2016, and despite sustained domestic demand and the introduction of new cultivars, banana yield in Brazil has stagnated around 14.5 t ha−1 mainly due to nutrient and water mismanagement. “Prata” is now the dominant subgroup in N-E Brazil and is fertigated at high costs. Nutrient balances computed as isometric log-ratios (ilr) provide a comprehensive understanding of nutrient relationships in the diagnostic leaf at high yield level by combining raw concentration data. Although the most appropriate method for multivariate analysis of compositional balances may be less efficient due to non-normal data distribution and limited nutrient mobility in the plant, robustness of the nutrient balance approach could be improved using Box-Cox exponents assigned to raw foliar concentrations. Our objective was to evaluate the accuracy of nutrient balances to diagnose fertigated “Prata” orchards. The dataset comprised 609 observations on fruit yields and leaf tissue compositions collected from 2010 to 2016 in Ceará state, N-E Brazil. Raw nutrient concentration ranges were ineffective as diagnostic tool due to considerable overlapping of concentration ranges for low- and high-yielding subpopulations at cutoff yield of 40 Mg ha−1. Nutrient concentrations were combined into isometric log-ratios (ilr) and normalized by Box-Cox corrections between 0 and 1 which may also account for restricted nutrient transfer from leaf to fruit. Despite reduced ilr skewness, Box-Cox coefficients did not improve model robustness measured as the accuracy of the Cate-Nelson partition between yield and the multivariate distance across ilr values. Sensitivity was 94%, indicating that low yields are attributable primarily to nutrient imbalance. There were 148 false-positive specimens (high yield despite nutrient imbalance) likely due to suboptimal nutrition, contamination, or luxury consumption. The profitability of “Prata” orchards could be enhanced by rebalancing nutrients using ilr standards with no need for Box-Cox correction.

Changing perspectives in screening for congenital hypothyroidism and congenital adrenal hyperplasia

The purpose of this review is to summarize recent information that has had a significant impact on the laboratory diagnosis and clinical management of newborns with congenital hypothyroidism and congenital adrenal hyperplasia (CAH). An approximate doubling of the incidence rate of congenital hypothyroidism in many parts of the world has been attributed to increased detection of infants with mild disease, delayed thyroid stimulating hormone elevations and demographic changes. A substantial number of children with modest thyroid stimulating hormone elevations on screening have permanent disease. Circulating levels of thyroxine may vary among hypothyroid children who are given identical dosages of medication. Treated infants should be monitored every 1-2 months during the first year of life. Although, generic and brand name thyroxine preparations may not be bioequivalent, children can be well controlled on generic formulations.Enzyme linked immunoassay assay for 17-hydroxyprogesterone is associated with a high rate of false positive specimens. In attempts to minimize this problem, some programs have resorted to two-tier screening of the initial specimen with steroid profiling as the second tier. Several programs are routinely testing second specimens in an effort to reduce the incidence of missed CAH cases. This review explains the uptick in incidence rate of congenital hypothyroidism and underscores issues in management that can affect developmental outcome. One specimen two-tier testing for CAH resulted in an increased false negative rate without significantly reducing the false positive rate. The benefit of collecting second specimens for CAH screening is problematic. Optimal treatment of CAH continues to pose a challenge.

Evaluation of Leukocyte and Bacterial Interference in Point-of-Care Human Chorionic Gonadotropin Tests

We read with interest the Letter to the Editor by Jao et al. [1] which reported false positive results using the point-of-care (POC) One Step Pregnancy Test device (ACON Laboratories Inc., San Diego, CA, USA). The authors determined that false positive results occurred when the concentration of white blood cells (WBCs) in a urine specimen exceeded 0.4×109 cells/L. We recently observed several false-positive human chorionic gonadotropin (hCG) results using the POC hCG Combo Rapid Test (Cardinal Health, Waukegan, IL, USA). We observed that most of our false positive specimens were in patients with evidence of urinary tract infection (UTI) and pyuria; with this information, and in the context of the findings by Jao et al. [1] that WBCs may result in false positive hCG assays, we evaluated the effect of WBCs or bacteria in urine on the analytical performance characteristics of both devices. Two buffy coat preparations were created using pooled whole blood from 25 patients. The buffy coat preparations were analyzed using the Coulter LH 750 Hematology Analyzer (Beckman Coulter, Brea, CA, USA) to assess the purity of the preparation. WBCs were prepared on two separate occasions and the total WBC counts of the pools were 57.5×109/L and 200×109/L. These WBC preparations were then diluted into urine from a male patient at six different WBC concentrations (0.1×109, 0.4×109, 1.0×109, 5.0×109, 10.0×109, and 21.0×109/L) including and exceeding the concentration used by Jao et al. [1]. The urine was then tested on both the hCG One Step and the hCG Combo Rapid test according to the manufactures' recommendations. All specimens were negative on both devices. The explanation for the different results observed in the study by Jao et al. [1] and the current study are unclear. Jao et al. [1] do not describe the source of their WBC preparation, it is unknown if it is from one patient or multiple patients, and the WBC differential is also unknown. It is possible that differences in these parameters could explain the discrepancy. With the knowledge that most of our patients with false positive results had evidence of UTI, and knowing that Escherichia coli is the most common cause of UTI in the outpatient setting, we wondered if E. coli specifically might account for the false positive results. To test this hypothesis, we made logarithmic dilutions (107 colony forming units [CFU]/mL, 106 CFU/mL and 105 CFU/mL) of a clinical isolate of uropathogenic E. coli into sterile urine from a male patient and tested these samples on both devices; all tests yielded negative results. To account for the fact that addition of E. coli and/or WBCs to sterile urine might not accurately replicate the matrix of a clinical specimen from a patient with UTI, we then tested 10 urine specimens from unique, female patients that were culture positive for E. coli (>50,000 colonies/mL) and 5 additional urine specimens that were submitted from outpatients to the microbiology laboratory for culture for presumed UTI. All of these specimens, when tested with the hCG Combo Rapid Test, also gave negative results. A recent study by Snyder et al. [2] reported that high WBC concentrations resulted in falsely increased serum hCG concentrations using the Beckman Coulter Access Total βhCG on the UniCel DxI (Beckman Coulter, Chaska, MN, USA). According to the authors, the false positive results may be attributed to leukocyte alkaline phosphatase reacting with the conjugate that is used in those immunoassays. However, both POC devices used in this particular study use colloidal gold as the color conjugate, hence leukocyte alkaline phosphatase should not result in this specific interference. Based on the information in this study, we feel there is inadequate evidence at this time to conclude that false-positive hCG results, in either the One Step Pregnancy Test device or the hCG Combo Rapid Test, can be attributed to elevated WBC concentrations in the urine. However, we continue to see false positive results that suggest the presence of a yet unidentified interfering substance.

Multicenter Clinical Evaluation of the illumi gene Group A Streptococcus DNA Amplification Assay for Detection of Group A Streptococcus from Pharyngeal Swabs

Acute pharyngitis is a nonspecific symptom that can result from a number of viral or bacterial infections. For most etiologies, symptoms are self-limited and resolve without lasting effects; however, pharyngitis resulting from infection with Streptococcus pyogenes (a group A Streptococcus [GAS]) can be associated with serious sequelae, including acute rheumatic fever and acute glomerulonephritis. Rapid accurate detection of GAS in pharyngeal specimens from individuals suffering from pharyngitis aids in the management and selection of antibiotic therapy for these patients. A total of 796 pharyngeal swabs were collected at three separate clinical centers. Each specimen was analyzed using the illumigene group A strep DNA amplification assay (Meridian Bioscience Inc., Cincinnati, OH). To confirm GAS identification, the results were compared to those from direct and extracted culture methods using Gram staining and a GAS-specific latex agglutination test. Discrepant results were resolved using an alternative nucleic acid amplification test. The prevalence of culture-detected GAS in this study was 12.8% (102/796 specimens). The illumigene assay detected GAS in 74/74 direct culture-positive specimens (100% sensitivity) and 100/102 extracted culture-positive specimens (98.0% sensitivity). GAS was detected by the illumigene assay in an additional 42 specimens that were direct culture negative (94.2% specificity) and 16 specimens that were extracted culture negative (97.7% specificity). Discrepant analysis using an alternative molecular assay detected GAS nucleic acid in 13/16 (81.3%) false-positive specimens and 1/2 false-negative specimens, resulting in a final sensitivity of 99.0% and a specificity of 99.6% for the detection of GAS in pharyngeal swabs using the illumigene assay.

金コロイドを用いた新規イムノクロマト法による便中ノロウイルス検出試薬の有用性

We evaluated the usefulness of ImmunoCatch-Noro (Eiken Chemical Co., Ltd.) (IC-A), a newly developed immunochromatography kit using Au colloid, for the detection of norovirus in stool specimens collected from patients with acute gastroenteritis during the three-year period from 2008-2011. When a total of 316 specimens were tested by RT-PCR and direct sequencing of the PCR products, norovirus was detected in 198 specimens (62.7%), including nine genotypes (GI/2, GI/4, GI/8, GII/1, GII/2, GII/3, GII/4, GII/6 and GII/ 13). The most frequently isolated genotypes were GII/3 (64), GII/2 (59) and GII/4 (58), accounting for about 90% of the positive specimens. As compared to RT-PCR, the sensitivity, specificity and concordance rate of IC-A were 87.4% (173/198), 100% (118/118) and 92.1% (291/316), respectively. Twenty-five positive specimens that were positive by RT-PCR were negative by IC-A, however there were no false-positive results of IC-A. On the other hand, the commercially available immunochromatography kit (IC-B), which was tested for comparison, had a sensitivity, specificity and concordance rate of 59.6% (118/198), 96.6% (114/118) and 73.4% (232/316), respectively, containing 80 false-negative and four false-positive specimens. All of the 118 specimens positive by both IC-B and RT-PCR were also interpreted as positive by IC-A. The detection rates of the predominant genotypes (GII/2, GII/3 and GII/4) by IC-A were 88.1%, 87.5% and 89.7%, respectively. In contrast, those by IC-B were only 32.2%, 67.2% and 81.0%, respectively. These results show that IC-A had adequate sensitivity and cross-reactivity for a wide range of GI and GII genotypes, and also had high specificity. In conclusion, IC-A is a useful rapid-diagnostic kit for the detection of norovirus, however, its current application is limited for stool specimens.

False positivity of circumsporozoite protein (CSP)–ELISA in zoophilic anophelines in Bangladesh

Circumsporozoite protein enzyme-linked immunosorbent assays (CSP–ELISAs) are widely used for malaria vector identification throughout the world. However, several studies have reported false-positive results when using this method. The present study was conducted to estimate the frequency of false positives among anopheline species in malaria endemic areas of Bangladesh. In total, 4724 Anopheles females belonging to 25 species were collected and tested for Plasmodium falciparum, Plasmodium vivax-210, and P. vivax-247 CSP. Initially, 144 samples tested positive using routine CSP–ELISA, but the number of positive results declined to 85 (59%) when the samples were tested after heating at 100°C for 10min to remove false-positive specimens. Ten species, Anopheles annularis, Anopheles baimaii, Anopheles barbirostris, Anopheles jeyporiensis, Anopheles karwari, Anopheles kochi, Anopheles minimus s.l., Anopheles peditaeniatus, Anopheles philippinensis, and Anopheles vagus were CSP-positive. The highest and lowest infection rates were found in An. baimaii (4/25, 16.0%) and An. jeyporiensis (1/139, 0.67%), respectively. A significant correlation was found (regression analysis, R2=0.49, F=8.25, P<0.05) between human blood index results and the true CSP-positive ratios in 15 Anopheles species. We confirmed that false-positive reactions occurred more frequently in zoophilic species. The relatively high proportion of false positives (40%) that was found in this study should warn malaria epidemiologists working in the field to be cautious when interpreting ELISA results.

High Proportion of False-Positive Clostridium difficile Enzyme Immunoassays for Toxin A and B in Pediatric Patients

To determine the frequency of false-positive Clostridium difficile toxin enzyme immunoassay (EIA) results in hospitalized children and to examine potential reasons for this false positivity. Nested case-control. Two tertiary care pediatric hospitals. As part of a natural history study, prospectively collected EIA-positive stools were cultured for toxigenic C. difficile, and characteristics of children with false-positive and true-positive EIA results were compared. EIA-positive/culture-negative samples were recultured after dilution and enrichment steps, were evaluated for presence of the tcdB gene by polymerase chain reaction (PCR), and were further cultured for Clostridium sordellii, a cause of false-positive EIA toxin assays. Of 112 EIA-positive stools cultured, 72 grew toxigenic C. difficile and 40 did not, indicating a positive predictive value of 64% in this population. The estimated prevalence of C. difficile infection (CDI) in the study sites among children tested for this pathogen was 5%-7%. Children with false-positive EIA results were significantly younger than those with true-positive tests but did not differ in other characteristics. No false-positive specimens yielded C. difficile when cultured after enrichment or serial dilution, 1 specimen was positive for tcdB by PCR, and none grew C. sordellii. Approximately one-third of EIA tests used to evaluate pediatric inpatients for CDI were falsely positive. This finding was likely due to the low prevalence of CDI in pediatric hospitals, which diminishes the test's positive predictive value. These data raise concerns about the use of EIA assays to diagnosis CDI in children.

Evaluation of the performance of the Abbott ARCHITECT HIV Ag/Ab Combo Assay

Background Worldwide, many countries test for HIV infection using combination assays that simultaneously detect p24 antigen and HIV antibodies. One such assay, the ARCHITECT ® HIV Ag/Ab Combo Assay (ARCHITECT), has recently been approved by the Food and Drug Administration (FDA) for use in the United States. Objective To evaluate the performance of ARCHITECT on well-characterized specimens from four CDC-funded studies. Study design We evaluated 3386 HIV-infected, 7551 HIV-uninfected, and 58 acute HIV infection (AHI) specimens. HIV-infected specimens were repeatedly reactive by enzyme immunoassay (EIA) and Western blot (WB) or positive by nucleic acid amplification testing (NAAT). HIV-uninfected specimens were EIA- and NAAT-negative. AHI specimens were seronegative or indeterminate (using antibody-based EIAs, rapid tests or WB) and NAAT-positive. All specimens were de-identified and sent to Abbott Diagnostics for testing with ARCHITECT. ARCHITECT test results were compared to original study characterizations and were used to assess overall sensitivity and specificity and also sensitivity for AHI. ARCHITECT false-positive specimens with sufficient quantity were retested. Results Based on results from the initial ARCHITECT test, sensitivity was 99.94% (95% confidence interval [CI]: 99.79, 99.99) and specificity was 98.78% (95% CI: 98.51–99.01). Repeat testing resulted in corrected specificity of 99.50% (95% CI: 99.31, 99.64). Also, 48 AHI specimens (83%) were detected by this screening assay. Conclusion The sensitivity and specificity of the ARCHITECT combination assay are very high and most AHIs were detected by the assay. Use of Ag/Ab combination assays may improve the number of AHIs identified relative to existing FDA-approved HIV-antibody only based serologic assays, particularly in high incidence populations.

Performance of Xpert MTB/RIF RUO Assay and IS 6110 Real-Time PCR for Mycobacterium tuberculosis Detection in Clinical Samples

The Cepheid Xpert MTB/RIF research-use-only (RUO) assay and a laboratory-developed test (LDT) targeting IS6110 were evaluated and compared to mycobacterial culture as the gold standard. The performance characteristics of both molecular assays were determined by using 112 specimens from 90 patients, including 89 pulmonary specimens and 23 extrapulmonary specimens. Of the specimens tested, 37 (33%) were culture positive for the Mycobacterium tuberculosis complex; 29 were pulmonary, and 8 were extrapulmonary. Of these culture-positive specimens, 83% of the pulmonary specimens and 50% of the extrapulmonary specimens were smear positive. There was complete concordance between the smear-positive culture-positive specimens, independent of the anatomical site (100% sensitivity). The sensitivity of the MTB/RIF RUO assay for smear-negative specimens was 60% for pulmonary and 75% for extrapulmonary specimens, while the IS6110 LDT sensitivities were 40% and 0%, respectively. There was also complete concordance among the culture-negative specimens tested. Both assays showed 95% specificity, with four culture-negative specimens testing as positive. A review of patient records indicated that there was a high likelihood of the presence of M. tuberculosis complex DNA in the false-positive specimens. Biosafety analysis was performed and showed an acceptable reduction in organism viability using the processing methods described above. Both molecular assays are suitable for the detection of M. tuberculosis isolates in smear-positive pulmonary and extrapulmonary specimens, while the sensitivity of the detection of M. tuberculosis isolates in smear-negative specimens was variable.

False-positive EUS-guided FNA cytology for solid pancreatic lesions

The currently accepted paradigm is that the false-positive (FP) rate for EUS-guided fine-needle aspiration (EUS-FNA) cytologic analysis of a pancreatic lesion is less than 1%. To assess the FP rate of EUS-FNA in patients who underwent surgical resection for presumed pancreatic cancer. Retrospective study. Tertiary-care referral center. This study involved 367 patients with solid pancreatic lesions in whom EUS-FNA cytology results were interpreted as positive or suspicious for malignancy, which resulted in subsequent surgical resection. Surgical resection. The FP diagnosis was defined as EUS-FNA cytology specimens being reported as "positive" or "suspicious for malignancy" but that were later proven to be benign on surgical pathology. The FP rate for EUS-FNA was 4 of 367 (1.1%) when only "positive" cytology findings were interpreted as malignant and 14 of 367 (3.8%) when both suspicious and positive cytology findings were interpreted as malignant. Among the 4 cases falsely interpreted as positive, 1 was falsely diagnosed cytologically as a neuroendocrine tumor and 3 as adenocarcinomas. All FP specimens showed chronic pancreatitis on surgical pathology. The incidence of discordance between cytology and surgical pathology did not change over time (2000-2006: 8/188 [4.3%] vs 2007-2010: 6/179 [3.4%]; P = .79). Retrospective study at a single center. In a retrospective cohort trial, the FP rate for EUS-FNA of solid pancreatic lesions was 1.1%. Findings of the current study are in line with previous studies that have evaluated the FP cytology rates with EUS-FNA of solid lesions. FP cases transpired primarily as a result of cytologic misinterpretation in the setting of chronic pancreatitis.

P3-S6.05 Comparing the analytical sensitivities of six treponemal tests

BackgroundTraditional syphilis testing consists of screening with a non-treponemal test (RPR) and confirmation with a treponemal test (TP-PA, FTA-ABS, EIA, CIA, etc). Recently, that testing algorithm has been reversed due...

Mo1405 False Positive Endoscopic Ultrasound Guided Fine Needle Aspiration Cytology for Solid Pancreatic Lesions

choledocolithiasis (9), pancreatolithiasis (6), pancreatic duct stenosis (4) and other (3). ESCP was performed for malignant disease in 53 patients (69%). ERCP was not possible for difficult cannulation in 52 patients (67%) or an inaccessible ampulla in 25 patients (33%). Biliary and pancreatic drainage were attempted in 66 (86%) and 11 (14%) patients respectively, with a transgastric approach in 43 (56%) and transduodenal in 34 (44%). Ductography was achieved in 71/77 patients (92%), introduction of a wire into the biliary or pancreatic duct in 70/71 patients (98%), successful intraductal wire manipulation in 56/70 patients, rendezvous in 19/33, fistula dilation in 38/44 and transmural stent deployment in 31/38 patients. Technical success was achieved in 48 patients (62%) with clinical success in 45 of them. Intraductal wire manipulation was the most limiting stage and caused 16/29 failures. Complications occurred in 14 patients (18%) and as a direct consequence of them 4 patients passed away. Technical success was significantly better for endoscopists who performed more than 5 ESCP (75% vs 41%, p 0.004) and when the procedure was performed by 2 endoscopists (74% vs 52%, p 0.04). Other comparisons did not show a statistically significant influence on the final result. CONCLUSIONS: According to our data, outcomes of ESCP during its implantation stage in both community and referral hospitals reach a technical success of 62% with a complication rate of 18%. Intraductal manipulation of the wire seems to be the most difficult stage of the procedure. An experience of more than 5 ESCP and performance of the procedure by 2 endoscopists are factors which significantly improve the technical success of ESCP.

Enumeration of Nucleated Red Blood Cells with the ADVIA 2120 Hematology System: An International Multicenter Clinical Trial

The accurate, reproducible, and timely reporting of nucleated red blood cells (NRBC) is an important function of the clinical hematology laboratory. We used 960 samples from 5 worldwide sites to evaluate a new NRBC enumeration method for the ADVIA 2120 Hematology System. The method showed excellent correlation with microscopy (r = 0.93). Sensitivity and specificity for the presence of NRBC for all samples analyzed was 77.3% and 74.6%, respectively. Almost all false negative samples were at NRBC counts <or=10/100 white blood cells (WBC). All false negative samples and the vast majority of the false positive specimens would be identified in clinical practice by routine slide review of flagged results, using existing review criteria. The coefficient of variation of the method was <10% for NRBC counts >10/100 WBC. The NRBC method automatically corrects WBC counts and differential results for the presence of NRBC; the uncorrected counts are available to the user on the run screen. This method allows the enumeration of NRBC with the ADVIA 2120 Hematology System in CBC/DIFF sample mode without need for additional hardware, sample preparation, or reagents.

Valutazione di un test per la determinazione simultanea degli anticorpi e antigene p24 dell’HIV

A fourth generation immunoassay for the detection of antibodies to HIV-1 and HIV-2 and of HIV antigen p24 (Abbott Architect HIV Ag/Ab Combo) has been evaluated in comparison with two Ab-only third generation assays on 894 routine specimens and on preselected repository specimens.The Combo assay showed a better specificity (99.88% vs. 99.43-99.83%) and an analytical sensitivity for p24 of 22 pg/mL on a BBI commercial panel. The Architect assays gave a negative result on 22/24 repository false positive specimens from 18 subjects and, conversely, was positive on all the 39 repository specimens from 24 HIV-positive patients. On six patients with acute HIV infection the Architect assay gave an earlier positivity than the antibody-only assays (EIA and WB) on three cases, all viremic and positive for HIV p24.The performance characteristics of the new HIV Combo assay guarantee an advanced clinical sensitivity and a high specificity.

Performance of ORTHO® HCV core antigen and trak‐C™ assays for detection of viraemia in pre‐seroconversion plasma and whole blood donors

Logistics and cost of nucleic acid amplification testing (NAT) screening preclude its current use in many developing countries. Development of hepatitis C virus (HCV) core antigen assays offer an alternative to NAT. We evaluated two specimen populations to assess the sensitivity, relative to NAT, of the HCV core antigen (HCVcAg) ELISA (enzyme-linked immunosorbent assay) test system and the trak-C assay: (1) plasma donor HCV NAT-conversion panels and (2) cross-sectional whole blood donor NAT yield specimens. Differential sensitivities among NAT (NGI; Chiron/Gen-Probe) and both HCVcAg assays (Ortho-Clinical Diagnostics, Rochester, NY) were evaluated using: (1) 102 serial ramp-up phase specimens from 37 plasma donor NAT-conversion panels (Alpha Therapeutic/BioClinical Partners); and (2) 42 cross-sectional whole blood donor NAT yield specimens (confirmed RNA positive, antibody negative) plus 54 NAT false-positive specimens (American Red Cross). Viral load among the plasma donor NAT-conversion panels at the cutoffs for HCVcAg and trak-C assays were 32 000 copies/ml (95% confidence interval [CI] 8000-120 000) and 8000 copies/ml (95% CI: 2200-28 000), respectively. The mean (95% CI) difference in window period reduction compared to routine mini-pool NAT screening (estimated sensitivity 100 copies/ml) was delayed 5.2 days (2.2-7.6 days) for HCVcAg assay and 3.8 days (2.1-5.5 days) for the trak-C assay. Among the 42 NAT yield specimens, the HCVcAg assay detected 31 (74%) as core antigen-positive while the trak-C assay detected 37 (88%) as core antigen-positive. Viral loads for the five specimens not detected by the trak-C HCVcAg assay ranged from 100 to 7770 copies/ml. All 54 NAT false-positive specimens were non-reactive on both HCV core antigen assays. These data indicate that the trak-C assay has sensitivity approaching routine mini-pool NAT screening for the detection of seronegative HCV infection. In the absence of routine NAT screening for early HCV infection, the use of an HCV core antigen assay should be considered.