Reducing Specimen Rejection Rates Using Concentration-Dependent Hemolysis Rejection Thresholds.

BACKGROUND: Using middleware solutions, it is possible to implement concentration-dependent analyte-specific hemolysis rejection limits. This makes day-to-day reporting of clinical specimens more efficient and potentially lowers sample rejection rates compared to a "one-size-fits-all" approach (i.e., solely based on a single cutoff provided in the package insert). METHODS: Hemolysis interference studies were performed at multiple analyte concentrations for three frequently ordered tests. For each assay, concentration-dependent hemolysis rejection limits were designed based on the total allowable error (TAE) for the analyte as well as the clinical significance of such incurred inaccuracy at the respective concentrations. In general, the following rationale was used: if the interference exceeds 10% (or package insert cutoffs), a comment is placed on the result. If the interference exceeds the TAE, the result will not be reported. Reduction in specimen rejection rates were estimated by comparing the incurred specimen rejection rates when package inserts' vs concentration-dependent hemolysis interference limits were applied to a data set in our institute during a three-month period. RESULTS: Concentration-dependent analyte-specific hemolysis rejection thresholds were designed for three commonly ordered assays that are especially susceptible to hemolysis interference. It is estimated that these novel thresholds for aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and direct bilirubin (DBIL) reduced specimen rejection rates from 9.3% to 1.3%, 31.4% to 4.8%, and 19.9% to 7.1%, respectively. CONCLUSIONS: Concentration-dependent analyte-specific hemolysis rejection thresholds for three commonly ordered assays can reduce rejection rates without significantly compromising the quality of test results.

Use of a Vanadate Oxidation Conjugated Bilirubin Assay to Reduce Test Cancellations Resulting from Hemolyzed Specimens in Pediatric Patients.

OBJECTIVES: We sought to replace the highly hemolysis-susceptible diazo conjugated bilirubin (Bc) assay with the more robust vanadate oxidation method and determine its impact on test cancellation in the pediatric population. METHODS: Analytical validation of the Randox vanadate assay and comparison with the Roche diazo method were performed. The frequency of pediatric sample cancellation because of hemolysis was compared between the diazo and vanadate methods by retrospective analysis of clinical test data. RESULTS: The vanadate assay demonstrated no clinically significant interference from hemolysis up to a hemolysis index of 1,300 (approximately 13 g/L hemoglobin). There was a strong correlation with the diazo method (r2 = 0.97) but with a positive slope bias of 1.27. Implementing the vanadate method resulted in a significantly lower proportion of pediatric samples cancelled because of hemolysis compared with the diazo method (0.6% of 688 patients vs 30.6% of 10,464 patients, respectively; P < .001), with a 0.6% (n = 513) vs 43.2% (n = 6,464) reduction in test cancellations (P < .001) for children younger than 6 months of age. CONCLUSIONS: The vanadate method showed robust performance against hemolysis. Its implementation resulted in a significant decrease in pediatric tests cancelled because of hemolysis.

Analytical and Clinical Evaluation of the Semiquantitative Elecsys Anti-SARS-CoV-2 Spike Protein Receptor Binding Domain Antibody Assay on the Roche cobas e602 Analyzer.

OBJECTIVES: To analytically and clinically evaluate the semiquantitative Elecsys anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein antibody (S-Ab) assay on the Roche cobas e602 analyzer. METHODS: The S-Ab assay is a 1-step, double-antigen sandwich electrochemiluminescent immunoassay that semiquantitatively measures total IgG, IgM, and IgA antibodies specific for the receptor binding domain of SARS-CoV-2 spike protein in serum or plasma. The S-Ab assay was evaluated for precision, linearity, interference (by hemoglobin, bilirubin, triglycerides, and biotin), cross-reactivity, and clinical performance, and was compared to the qualitative Elecsys anti-nucleocapsid (N-Ab) immunoassay, a lateral flow device that qualitatively detects S-Ab and N-Ab, and an anti-spike enzyme-linked immunosorbent assay (ELISA). RESULTS: S-Ab assay is precise, exhibits linearity from 0.4 to 250 U/mL, is unaffected by significant cross-reactivity or interferences, and qualitatively demonstrates greater than 90% concordance with N-Ab assay and lateral flow device. Readouts of S-Ab assay correlate with ELISA, which in turn correlates strongly with SARS-CoV-2 virus neutralization assay, and exhibit 100% sensitivity and specificity for COVID-19 patient samples obtained at or more than 14 days after PCR positivity. CONCLUSIONS: The S-Ab assay is a robust clinical test for qualitative and semiquantitative detection of seropositivity following SARS-CoV-2 infection or spike-encoding mRNA COVID-19 vaccination.