Improved efficiency using sequential automated immunoassays for syphilis screening in blood donors

Area of Science:

• Clinical diagnostics and infectious disease screening
• Serological testing methodologies

Background:

• Traditional syphilis serodiagnosis involves non-treponemal then treponemal tests, or vice versa.
• Modified reverse algorithms using two treponemal tests are less reported.
• The withdrawal of the Treponema pallidum particle agglutination (TPPA) assay necessitates alternative diagnostic strategies.

Purpose of the Study:

• To evaluate the performance of sequential automated immunoassays for syphilis screening in blood donors.
• To assess the feasibility of using a modified reverse algorithm with two treponemal immunoassays.
• To provide proof of concept for an alternative syphilis serodiagnosis algorithm.

Main Methods:

• Screened 1,767,782 blood donor samples using the Alinity s Syphilis assay.
• Repeatedly reactive samples were tested on the Elecsys Syphilis assay.
• Concordantly reactive samples underwent confirmatory testing with TPPA, RPR, and FTA-ABS.

Main Results:

• The Alinity s Syphilis assay showed a low false-positive rate of 0.08%.
• The common false-positive rate between Alinity and Elecsys assays was 3.83%.
• Of 1,376 concordantly reactive samples, 26 had current syphilis, 152 had treated past syphilis, and 84 had no reported history.

Conclusions:

• Sequential immunoassays with Alinity and Elecsys syphilis tests are effective for blood donor screening.
• This methodology demonstrates a low false-positive rate and identifies current and past syphilis infections.
• Sequential immunoassays represent a promising alternative for syphilis serodiagnosis, addressing the need for new algorithms.