Background:
Historically, non-treponemal tests have been used for syphilis screening in the US, and treponeme-specific tests used for confirmatory testing. Changing the testing order from non-treponemal/treponemal to treponemal/non-treponemal changes the positive predictive value (PPV) of a treponemal test; differing approaches to retesting IgG positive specimens may also impact the positive and negative predictive value of tests. Physicians and STD program staff following up on positive syphilis IgG EIA's need to be acquainted with the correct interpretation of such tests.


Objective:
To describe syphilis testing algorithms employed by NYC clinical laboratories (labs) screening with the syphilis IgG EIA.

Method:
We contacted 4 NYC labs screening with syphilis IgG and requested information regarding testing sequences and testing volume. A diagram was made of each lab's testing sequence.

Result:
Together, the 4 labs performed >200,000 syphilis IgG tests in 2004. Lab #1 and #4 retested IgG positive, RPR non-reactive specimens with a second, alternate treponemal test (FTA or TPPA) before reporting the result. Lab #2 did only an IgG and RPR, and no further testing, and Lab #3 repeated an IgG on all positive syphilis IgG (on the same specimen) and then used an alternate treponemal test (TPPA) to test IgG positive, RPR reactive specimens.

Conclusion:
NYC labs using the syphilis IgG do a high volume of testing and are using different testing sequences.

Implications:
Further analyses will examine how using a treponemal test as a screening test impacts on patient treatment and the time spent by field staff in follow up.