Evaluation of the fully automated AIX1000 rapid plasma reagin system compared to a manual plasma reagin testing method for the diagnosis of syphilis

• Published in: Diagnostic microbiology and infectious disease Vol. 97; no. 4; p. 115081
• Main Authors: Pyden, Alexander, Kang, Anthony D., Amato, Sheryl, Dutta, Sanjucta, Berg, Gretchen, Riedel, Stefan
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.08.2020
• Subjects: AIX1000; Algorithms; Antibodies, Bacterial - blood; Automation, Laboratory; Diagnostic Tests, Routine; Humans; Laboratory automation; Reagins - blood; RPR; Sensitivity and Specificity; Syphilis; Syphilis - diagnosis; Syphilis Serodiagnosis - methods; Syphilis Serodiagnosis - standards; Treponema pallidum - immunology; Treponema pallidum - isolation & purification; AIX1000; Laboratory automation; RPR; Syphilis
• ISSN: 0732-8893; 1879-0070
• DOI: 10.1016/j.diagmicrobio.2020.115081

The analytical performance of the FDA-cleared AIX1000 automated RPR testing platform was evaluated in comparison to manual RPR card testing. Eight hundred thirty-three patient serum samples were analyzed, 87 samples were positive by the AIX1000, 108 were positive by the manual test method; overall agreement between methods was 96.5% (κ = 0.83). Cases were further classified by clinical and laboratory-based confirmation of disease, to which reactivity rates were compared, yielding sensitivities of 96.4% and 100%, and specificities of 99.2% and 96.8% for the automated and manual RPR methods, respectively. The difference in specificity between methods was statistically significant (P < 0.001). Twenty-five of 29 samples with discordant results were reactive by manual testing (titers of 1:1 or 1:2); 21 of 25 patients with negative AIX100 results were identified to have histories of remote, treated syphilis. Overall, the AIX1000 platform demonstrated excellent agreement with the manual RPR method; discrepancies occurred with specimens at the threshold of reactivity.