Utility of Commercially Available Quantitative hCG Immunoassays as Tumor Markers in Trophoblastic and Non-Trophoblastic Disease.

BACKGROUND: The use of quantitative human chorionic gonadotropin (hCG) as a tumor marker is widely accepted despite lack of FDA-approval for oncology. Differences in iso- and glycoform recognition among hCG immunoassays is well established, exhibiting wide inter-method variability. Here, we assess the utility of 5 quantitative hCG immunoassays for use as tumor markers in trophoblastic and non-trophoblastic disease. METHODS: Remnant specimens were obtained from 150 patients with gestational trophoblastic disease (GTD), germ cell tumors (GCT), or other malignancies. Specimens were identified by review of results from physician-ordered hCG and tumor marker testing. Five analyzer platforms were used for split specimen analysis of hCG: Abbott Architect Total, Roche cobas STAT, Roche cobas Total, Siemens Dimension Vista Total, and Beckman Access Total. RESULTS: Frequency of elevated hCG concentrations (above reference cutoffs) was highest in GTD (100%), followed by GCT (55% to 57%), and other malignancies (8% to 23%). Overall, the Roche cobas Total detected elevated hCG in the greatest number of specimens (63/150). Detection of elevated hCG in trophoblastic disease was nearly equivalent among all immunoassays (range, 41 to 42/60). CONCLUSIONS: While no immunoassay is likely to be perfect in all clinical situations, results for the 5 hCG immunoassays evaluated suggest that all are adequate for use of hCG as a tumor marker in gestational trophoblastic disease and select germ cell tumors. Further harmonization of hCG methods is needed as serial testing for biochemical tumor monitoring must still be performed using a single method. Additional studies are needed to assess the utility of quantitative hCG as a tumor marker in other malignant disease.

Recommendations for validation testing of home pregnancy tests (HPTs) in Europe.

Home pregnancy tests (HPTs) available in Europe include accuracy and other performance claims listed on their packaging. Due to the lack of guidance on the standardisation of such products, it is often difficult to replicate these claims when tested on a clinical sample, whether in a laboratory setting or by lay users. The In Vitro Diagnostic Regulation is a set of requirements that mandate comprehensive validation data on human pregnancy tests and other in vitro devices. It is due to replace the current European Directive (98/79/EC) and fully implemented in Europe by 2022. In June 2019, a panel of seven experts convened to discuss the validation studies required to provide the information needed to meet the new regulation for HPTs in Europe and proposed 15 recommendations for best practice. Defining best practice at all stages of validation of these important tests may ensure that tests marketed in Europe are fit for purpose, enabling lay users to be confident of the high quality of the HPT results they obtain. The panelists believe that the recommendations proposed here for the validation of HPTs may constructively contribute to improved standardisation of validation procedures in Europe.

Evaluation of the automated LIAISON® SARS-CoV-2 TrimericS IgG assay for the detection of circulating antibodies.

OBJECTIVES: COVID-19 has brought about tests from many manufacturers. While molecular and rapid antigen tests are targeted for early diagnosis, immunoassays have a larger role in epidemiological studies, understanding longitudinal immunity, and in vaccine development and response. METHODS: The performance of the LIAISON® SARS-CoV-2 TrimericS IgG assay was evaluated against the Beckman ACCESS SARS-CoV-2 IgG assay in New Mexico, and against the Siemens ADVIA Centaur COV2G assay in New York. Discordant samples were parsed using a microneutralization assay. RESULTS: A SARS-CoV-2 antibody positivity rate of 23.8% was observed in the samples tested in New York (September 2020), while in the same month the positivity rate was 1.5% in New Mexico. Positive and negative agreement were 67.6% (95% CI 49.5-82.6%) and 99.8% (95% CI 99.5-99.9%), respectively, with the Beckman test, and 98.0% (95% CI 95.7-99.3%) and 94.8% (95% CI 93.4-96.0%), respectively, with the Siemens test. Receiver operating characteristic analysis for the detection of SARS-CoV-2 antibodies discloses an AUC, area under the curve, of 0.996 (95% CI 0.992-0.999) for the LIAISON® SARS-CoV-2 TrimericS IgG assay. The criterion associated to the Youden Index was determined to be >12.9 kAU/L with a sensitivity of 99.44% and a specificity of 99.82%. CONCLUSIONS: The LIAISON® SARS-CoV-2 TrimericS IgG assay is highly sensitive and specific. The balance of these parameters, without emphasis on high specificity alone, is particularly important when applied to high prevalence populations, where a highly sensitive assay will result in reporting a lower number of false negative subjects.

The relationship between PTH and 25-hydroxy vitamin D early in pregnancy.

OBJECTIVE: Measure serum PTH and 25(OH)D in a cross-sectional sample of pregnant women at 11th through 13th weeks' gestation to examine vitamin D status and consider implications. DESIGN: Observational: we retrieved residual sera stored at -20 °C after routine first trimester Down's syndrome screening, distributed over 12 months. PATIENTS: 430 African American women and 586 Caucasian women. MEASUREMENTS: PTH and 25-hydroxy vitamin D [25(OH)D] immunoassays. RESULTS: PTH medians were: 1·33 pmol/l (African American women); 1·20 pmol/l (Caucasian women) (t = 0·43, P = 0·7). Concentrations were highest in winter and decreased significantly in spring, fall, and summer. There was a direct PTH/weight relationship in Caucasian (t = 3·12, P < 0·002), but not African American women (t = 1·34, P = 0·18). Median 25(OH)D concentrations were 47·5 nmol/l (African American women) and 65 nmol/l (Caucasian women) (t = 13·7, P < 0·001). Concentrations were lowest in winter and rose significantly in spring, fall, and summer. Reciprocal 25(OH)D/weight relationships existed for both racial groups (t =-4·31 P < 0·001; t = 4·54, P < 0·001, respectively). Among 68 Caucasian women who smoked, median PTH and 25(OH)D concentrations were somewhat lower (P = ns). In separate regression models with PTH and 25(OH)D [dependent variables] and season, weight and smoking [independent variables], the only qualifying interactive term was in the Caucasian PTH model (season*1/weight). A regression model applied to adjusted scatter plots of PTH vs 25(OH)D indicated a weak relationship. CONCLUSIONS: The PTH/25(OH)D relationship is weaker during early pregnancy than in non-pregnant adults, making it unreliable for estimating vitamin D sufficiency. A suitable reference point for sufficiency might be the maternal 25(OH)D level considered sufficient for adequate transfer to neonates.

Correlation of SARS-CoV-2 Neutralizing Antibodies to an Automated Chemiluminescent Serological Immunoassay.

INTRODUCTION: Neutralizing antibodies (NAbs) are capable of binding to a virus to render it incapable of infection. The ability of commercially available SARS-CoV-2 serological tests to detect NAbs has not been widely reported. We sought to correlate the antibodies detected by an automated chemiluminescent immunoassay with NAbs. METHODS: Residual serum samples from 35 patients that had a positive antibody test using the LIAISON® SARS-CoV-2 S1/S2 IgG chemiluminescent immunoassay and 2 antibody-negative control sera were tested for NAbs using a plaque reduction neutralization test (PRNT). RESULTS: NAbs were detected in 66% (23/35) of the antibody-positive samples. The immunoassay signal value ranged from 21.7 to 131.3 AU/mL (median, 90.5) with significant correlation between it and the PRNT (r = 0.61, P = 0.002). In the samples without NAbs, the immunoassay signal ranged from 16.3 to 66.2 AU/mL (median, 27.2). An immunoassay signal cutoff of >41 AU/mL was 91% sensitive and 92% specific for the detection of NAbs. DISCUSSION: It is important that correlates of immunity to SARS-CoV-2 be identified and NAbs are considered to be central indicators of such. PRNT is the gold-standard test for identifying NAbs but it cannot be used for large-scale testing of populations. It is necessary to establish relationships between it and widely used commercial serological assays for SARS-CoV-2.

Leveraging longitudinal clinical laboratory results to improve prenatal care.

OBJECTIVES: To assess the impact of providing laboratory-generated near-real-time clinical insights for pregnant Medicaid members to managed care organization (MCO) care coordinators. STUDY DESIGN: A prospective, nonrandomized feasibility study was conducted over 11 months to examine the benefits of laboratory-generated clinical insights on prenatal care quality metrics and clinical outcomes. Measures included early identification of pregnancy and births to facilitate care, care gaps with prenatal laboratory testing, emergency department (ED) visits, preterm births, and neonatal intensive care unit (NICU) admissions and length of stay. METHODS: Weekly MCO care coordinators were provided a laboratory-generated prenatal targeted intervention module (TIM) to supplement their existing systems in a longitudinal, patient-centric format. Care coordinators contacted patients for enrollment in prenatal or postpartum services based on the TIM, which identified concomitant health conditions, missing prenatal care, and risks. RESULTS: The prenatal TIM identified 1355 pregnant members, 77% (n = 1040) of whom were detected in the first trimester. A total of 488 births were identified within 24 hours of parturition. Sixty-four percent of women had at least 80% of prenatal care gaps associated with laboratory testing closed. Women with ongoing prenatal care had fewer ED visits (17% vs 23%) and NICU admissions (11% vs 18%) compared with those without prenatal care. After adjusting for confounders, ongoing prenatal care had a borderline effect at decreasing the probability of having an ED visit and a NICU admission. CONCLUSIONS: An innovative collaboration between an MCO and a clinical laboratory improved quality measures for prenatal members enrolled in Medicaid.

Immunoassay for quantifying squamous cell carcinoma antigen in serum.

BACKGROUND: Although the benefits of quantifying serum squamous cell carcinoma antigen (SCCa) have been reported, SCCa reagents were no longer available in the US by the late 1990s. Because SCCa quantification still has demonstrated clinical utility, we developed and validated a microtiter plate-based ELISA for measuring SCCa in serum. METHODS: We coated microtiter strips overnight with capture anti-SCCa monoclonal antibody, washed the wells, added blocking buffer, and lyophilized the strips. For detection, we used a biotinylated anti-SCCa detection antibody, streptavidin/horseradish peroxidase conjugate, and tetramethylbenzidine/H(2)O(2) substrate. A novel blocking reagent against human antimouse antibodies (HAMA) was evaluated. A reference interval was established with sera from healthy individuals and was confirmed in smokers. RESULTS: The assay was linear to 40 microg/L SCCa (slope, 1.00; y intercept, 0.695; R(2), 0.996) with a detection limit of 0.3 microg/L. The intraassay imprecision results [mean (CV)] were 2.5 microg/L (3.4%), 18.0 microg/L (3.0%), and 30.7 microg/L (2.4%); interassay imprecision results were 2.0 microg/L (9.9%), 20.0 microg/L (7.6%), and 36.3 microg/L (3.5%). A correlation analysis against an established automated assay generated a slope of 0.976 and a y intercept of -0.193 microg/L (r(2) = 0.916). An upper reference limit of 2.1 microg/L SCCa was established at 95% confidence level, with no difference observed in smokers. No correlation between SCCa concentration and age was observed (r(2) = 0.0003). At a blocking reagent concentration of 5 mg/L, HAMA interference was eliminated in 3 samples known to produce falsely increased SCCa results. CONCLUSIONS: This SCCa ELISA demonstrates acceptable performance characteristics for quantifying serum SCCa and is effective in eliminating HAMA interference.

Falsely decreased human chorionic gonadotropin (hCG) results due to increased concentrations of the free beta subunit and the beta core fragment in quantitative hCG assays.

BACKGROUND: Earlier studies have shown that increased concentrations of certain human chorionic gonadotropin (hCG) variants can cause false-negative results in some qualitative hCG devices. The objective of this study was to determine if increased concentrations of hCGß and hCGß core fragment (hCGßcf) cause falsely decreased results on 9 commercially available quantitative hCG assays. METHODS: Several concentrations of purified hCGß and hCGßcf were added to 2 sets of 6 serum samples with and without a fixed concentration of intact hCG. We examined 9 widely used immunoassays to measure immunoreactive hCG. Falsely decreased results were defined as those in which the measured hCG concentration was ≤50% of expected. RESULTS: High concentrations of hCGß (≥240 000 pmol/L) produced falsely decreased hCG measurements in 2 assays known to detect this variant. Similarly, high concentrations of hCGßcf (≥63 000 pmol/L) produced falsely decreased hCG measurements in 3 assays that do not detect purified hCGßcf. Two assays were identified that detected both hCGß and hCGßcf, and neither produced falsely decreased results in the presence of high concentrations of these variants. CONCLUSIONS: Extremely high concentrations of hCG variants can cause falsely decreased results in certain quantitative hCG assays. Of the 9 assays examined, none exhibited falsely decreased results in the presence of hCGß concentrations typically associated with hCGß-producing malignancies. Two assays exhibited decreased (>50%) hCG results in the presence of hCGßcf concentrations found during normal pregnancy.

Current Practices When Reporting Quantitative Human Chorionic Gonadotropin Test Results.

BACKGROUND: Quantitative human chorionic gonadotropin (hCG) tests are commonly used to determine a woman's pregnancy status. Discrete results are evaluated and/or interpreted against a reference interval or cutoff. Reporting practices across laboratories have not been investigated. METHODS: A voluntary questionnaire was distributed to 6433 laboratories participating in a general chemistry proficiency testing survey. RESULTS: Responses were received from 3568 (55%) laboratories. Overall, 31% used a single reference cutoff, with 42% and 14% using values of 5.0 and 25.0 IU/L, respectively. In total, 68% of laboratories provided result interpretations, most frequently "negative" and "positive." Reference intervals based on chronological age were offered by 9% of laboratories; 60% reported gestational age-based intervals. In addition, 25% provided male-specific reference intervals, with 2.0 IU/L being the most commonly used single-point cutoff. Only 12% of laboratories offered a separate, orderable test for hCG as a tumor marker, with 5.0 IU/L as the most frequently used reference threshold. Nearly half of laboratories used assay product insert data as the reference interval source. CONCLUSIONS: There is wide variation when reporting quantitative hCG results. Despite a well-established reference limit of <5.0 IU/L for nonpregnant women, fewer than half of laboratories used this cutoff. The reporting of gestational age-based reference intervals is more common than those based on chronological age despite greater clinical utility for the latter. Data-driven guidelines for reporting quantitative hCG test results could deliver more consistent result interpretation.

Development of an Automated Enzymatic Method to Quantify Pyruvate Kinase in Red Blood Cells.

BACKGROUND: Pyruvate kinase (PK) deficiency is the most common cause of nonspherocytic hemolytic anemia owing to defective glycolysis. This study developed and validated an automated method to measure PK activity in red blood cells (RBCs). METHODS: PK catalyzes the reaction of phosphoenolpyruvate with ADP to form pyruvate and ATP. The pyruvate is reduced in the presence of lactate dehydrogenase and NADH to produce lactate and NAD+. The rate of absorbance decrease at 340 nm is proportional to PK activity. PK and hemoglobin (Hb) measurements were performed on a Roche cobas c501 analyzer. After establishing a k-factor, accuracy, linearity, imprecision, sensitivity, and stability were validated and the reference interval was verified. RESULTS: The k-factor was -9477. Accuracy was evaluated by method comparison (n = 56). Linear regression yielded y = 1.0x - 0.57, and R2 of 0.93. Linearity was determined by combining a high sample with hemolyzing solution in 6 different ratios. Linear regression analysis yielded y = 1.02x - 2.68, and R2 of 1.0. The assay was linear to 87 U/dL. Precision was evaluated by testing hemolysates in 3 replicates/day for 10 days. Within-run imprecision was 1.9% and 2.5% and total imprecision was 4.0% and 5.6% at 14.0 and 8.1 U/g Hb, respectively. The limit of blank was 0.0, and the limit of detection was 1.0 U/dL. Stability was determined in 4 sample types at 3 different temperatures; the changes were all <10% when compared with t0. The current PK reference interval of 4.6 to 11.2 U/g Hb was verified. CONCLUSIONS: This automated assay for quantifying PK in RBCs has acceptable performance characteristics and is fit for intended use.

Performance comparison of capillary and agarose gel electrophoresis for the identification and characterization of monoclonal immunoglobulins.

The objective of this study was to compare gel- and capillary-based serum protein electrophoresis methods to identify and characterize monoclonal immunoglobulins (M proteins). Five reviewers interpreted 149 consecutively ordered serum specimens following agarose gel electrophoresis (AGE), capillary electrophoresis (CE), immunofixation electrophoresis (IFE), and subtraction immunotyping (IT). As a screening test for detecting M proteins, AGE and CE displayed similar sensitivity (91% and 92%, respectively). CE was less specific (74%) than AGE (81%). An analysis of interinterpreter agreement revealed that interpretations were more consistent using gel-based methods than capillary-based methods, with 80% of the gel interpretations being in complete (5/5) agreement compared with 67% of the capillary interpretations. After implementing the capillary-based methods, the number of tests per reportable result increased (from 1.58 to 1.73). CE is an analytically suitable alternative to AGE, but laboratories implementing it will need to continue IFE testing to characterize all M proteins detected by CE.

Evaluation of a fecal pancreatic elastase-1 enzyme-linked immunosorbent assay: Assessment versus an established assay and implication in classifying pancreatic function.

BACKGROUND: Disagreement continues regarding 2 fecal pancreatic elastase-1 (PE-1) ELISAs and their respective capabilities to assess pancreatic function. METHODS: The BioServ Diagnostics polyclonal PE-1 ELISA was validated and its performance characteristics compared to the previously validated ScheBo Biotech monoclonal PE-1 ELISA. Split sample study results were analyzed by Deming regression and Bland-Altman plot analysis. Data mining was utilized to explore PE-1 distribution and evaluate PE-1 and fecal fat correlation. RESULTS: Analysis demonstrates limited quantitative agreement; slope=0.9640, intercept=10.787, R(2)=0.633. Means were 228.8 and 226.2 microg PE-1/g stool for the polyclonal and monoclonal assays respectively. Bland-Altman analysis showed 91% of paired values within 2 SD of their means. There was good qualitative agreement when interpreted against established intervals with 91% of results equivalent in pancreatic function classification. The remaining 9% varied by one classification level with no bias evident. The distribution of PE-1 concentrations (n=400, 0-25 years) classified 78% of subjects with normal pancreatic function, 7% with moderate pancreatic insufficiency and 15% with severe insufficiency. There was little agreement between PE-1 and fecal fat results. CONCLUSIONS: The polyclonal PE-1 ELISA is an acceptable alternative to the monoclonal PE-1 ELISA. PE-1 is a potential substitute for fecal fat for evaluating pancreatic function.

Comparison of various methods for amniotic fluid DeltaOD450 bilirubin measurement.

BACKGROUND: The purpose of this study was to investigate the degree of DeltaOD450 method variability and its effect on DeltaOD450 measurements between selected clinical laboratories in the U.S. METHOD: Four amniotic fluid specimens were sent to 7 clinical laboratories in the U.S. for DeltaOD450 analysis. In addition, scanning spectrophotometric data from 152 amniotic fluid samples were used to compare DeltaOD450 values calculated using both log and linear OD scales. RESULTS: We found that no 2 laboratories used exactly the same method and no laboratory used precisely the same method as originally described by Liley. Despite the varied methods, the DeltaOD450 measurements were remarkably similar. The exception was 1 sample that was subjected to chloroform extraction. The DeltaOD450 measurement on this sample was 82% lower than the mean. On average, DeltaOD450 results determined from a linear OD scale were 37% lower than those determined from a log scale. CONCLUSION: Although there is no standard method for performing the DeltaOD450, inter-laboratory variation of DeltaOD450 results is remarkably small. As our and other previous studies have reported, these data suggest that both chloroform extraction and use of a linear scale have the potential to result in lower DeltaOD450 results.