Clinical application value of Abbott Alinity analyzer in syphilis-specific antibody testing

Abstract Background: We aimed to investigate the clinical application value of Abbott Alinity analyzer in syphilis-specific antibody testing. Methods: A total of 100 patients admitted from June 2021 to June 2022 for early syphilis diagnosis were selected and subjected to Treponema pallidum (TP) antibody testing by chemiluminescent microparticle immunoassay (CMIA) using Abbott Alinity analyzer. With TP particle agglutination (TPPA) retesting as the gold standard for syphilis diagnosis, the signal-to-cutoff (S/CO) ratio of the TP antibody testing was plotted into the receiver operating characteristic curve to determine the diagnostic value of CMIA and CLIA in detecting positive TP antibody and to identify the optimal cutoff point. Results: In the case of S/CO ratio ≥7.00, the patients with positive CMIA were diagnosed with positive findings after TPPA confirmation. With the S/CO ratio of 1.00-4.99, the coincidence rate of CLIA with positive TPPA was 81.82% (45/55), and all patients with positive CLIA had positive results confirmed by TPPA test when the S/CO ratio was >5.00. When the optimal cutoff value of S/CO ratio for TP was determined as 6.98 by CMIA, the sensitivity, specificity, and maximum area under the curve (AUC) were 94%, 88% and 0.91, respectively. At the optimal cutoff value (S/CO ratio: 4.56) determined by CLIA, the sensitivity was 84%, the specificity was 80%, and the maximum AUC was 0.84. Conclusions: In the case of S/CO ratio ≥7.00, both methods have high sensitivity and specificity, which can directly give positive reports and shorten the sample turnaround time.