Comparison of Four Systems for SARS-CoV-2 Antibody at Three Time Points after SARS-CoV-2 Vaccination.

BACKGROUND: Immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) wanes over time after vaccination. METHODS: We compared SARS-CoV-2 antibody levels in serial samples from 350 vaccinated individuals at 3 time points (3 weeks after the first or second dose and before the third dose) with 4 assays: GenScript cPASS SARS-CoV-2 neutralization antibody detection kits (cPASS), Siemens SARS-CoV-2 IgG (sCOVG), Abbott SARS-CoV-2 IgG II Quant (CoV-2 IgG II), and an Immuno-On™ COVID-19 IgG test (Immuno-On IgG). Antibody levels by time, concordance between assays, and values from other tests corresponding to the percent inhibition results in cPASS were assessed. RESULTS: The median values at three time points were 49.31%, 90.87%, and 53.38% inhibition for cPASS, 5.39, 13.65, and 2.24 U/mL for sCOVG, 570.25, 1279.65, and 315.80 AU/mL for CoV-2 IgG II, and 223.22, 362.20, and 62.20 relative units (RU) for Immuno-On IgG. The concordance with cPASS at each time point ranged from 0.735 to 0.984, showing the highest concordance in the second sample and lowest concordance in the third in all comparative tests. The values corresponded to 30% inhibition, and the cutoffs of cPASS, were 2.02 U/mL, 258.6 AU/mL, and 74.2 RU for each test. Those for 50%, 70%, and 90% inhibition were 3.16, 5.66, and 8.26 U/mL for sCOVG, while they were 412.5, 596.9, and 1121.6 AU/mL for CoV-2 IgG II and 141.8, 248.92, and 327.14 RU for Immuno-On IgG. CONCLUSIONS: This study demonstrated the dynamic changes in antibody values at different time points using four test systems and is expected to provide useful baseline data for comparative studies and standardization efforts in the future.

Performance evaluation of coaguchek pro II in comparison with coaguchek XS plus and sta-r Max using a sta-neoplastine CI plus.

INTRODUCTION: We evaluated the analytical performance of CoaguChek Pro II (Roche Diagnostics GmbH, Mannheim, Germany), a new point-of-care device measuring the international normalized ratio (INR) values, in comparison with CoaguChek XS Plus (Roche Diagnostics GmbH) and STA-R Max using STA-Neoplastine CI Plus (Diagnostica Stago SAS, Asnières-sur-Seine, France). METHODS: The precision of Pro II was analyzed, according to the Clinical and Laboratory Standards Institute guidelines (CLSI POCT14-A2 and EP15-A3). In 105 clinical samples, the Pro II INR values were compared with those of XS Plus and STA-R Max using STA-Neoplastine CI Plus (CLSI EP09-A3 and EP35). We also compared the Pro II INR values between capillary blood (CB) and venous blood (VB; CLSI EP35). RESULTS: The precision of Pro II was acceptable (within-run and between-run CV%: 2.71% and 3.28% at normal level; 1.52% and 4.47% at abnormal level, respectively). The Pro II INR values showed very high correlation and almost perfect agreement with those of XS Plus and STA-R Max using STA-Neoplastine CI Plus (r = .97 and κ = .94; r = .95 and κ = .91). The mean difference between Pro II and STA-R Max using STA-Neoplastine CI Plus increased as INR values increased, with 60% of samples showing differences >0.5 in the supratherapeutic range. The Pro II INR values showed very high correlation between CB and VB (r = .98). CONCLUSION: Pro II INR values are accurate and reliable using both CB and VB; however, they should be confirmed by laboratory analyzers in the supratherapeutic range.

Strategy for performing treponemal tests in reverse-sequence algorithms of syphilis diagnosis.

OBJECTIVES: In South Korea, automated T. pallidum Latex Agglutination (TPLA) based on turbidoimmunoassays and immunochromatographic assay (ICA) are widely used for syphilis diagnosis. However, there is sparse data on the validation of these assays in the reverse-sequence algorithm setting. METHODS: We assessed 551 specimens submitted for syphilis testing. We compared varying reverse-sequence algorithms using combinations of the Cobas Syphilis EIA (Roche Diagnostics, Mannheim, Germany), Mediace TPLA (Sekisui Medical Co., Tokyo, Japan), TPPA (Fujirebio Inc., Tokyo, Japan), and SD Bioline ICA (Standard Diagnostic, Yongin, Korea). We also evaluated modified algorithms incorporating a cut off of high specificity for EIA and TPLA using receiver operating characteristic curves. RESULTS: The agreement was almost perfect between EIA and TPLA (Kappa, 0.953) and strong between TPPA and ICA (Kappa, 0.887). Among TPPA positive and ICA negative specimens, 67% of the specimens were from individuals with syphilis histories. Compared to EIA/RPR/TPPA, the agreement with EIA/RPR/ICA, TPLA/RPR/TPPA and TPLA/RPR/ICA were almost perfect (Kappa, 0.930, 0.995 and 0.914, respectively). When a cut off of 95% specificity was applied, the number of TPPA tests could be reduced by 44% and 40% in EIA and TPLA, respectively. CONCLUSIONS: TPLA showed almost perfect agreement with EIA and that it could be used in the site of EIA in a reverse sequence algorithm. ICA showed a lower detection rate than TPPA as a 2nd treponemal test and should be used with caution. With cut offs of higher specificity, more efficient reverse-sequence algorithms can be made possible.