Evaluation of the Performance of a Rapid Syphilis Test, Syphilis Health Checktm, Using Finger-Stick Specimens in an STD Clinic in Escambia County, Florida, 2016

Background: In December 2014, the U.S. Food and Drug Administration granted the first-ever Clinical Laboratory Improvement Amendments waiver for a rapid treponemal syphilis screening test, Syphilis Health Check^TM (SHC^TM). We evaluated the performance of SHC^TM in comparison to treponemal and non-treponemal tests routinely used in an STD clinic.  

Methods: Patients seeking STD testing at the Florida Department of Health in Escambia County from 3/11/2016 through 4/21/2016 were tested for syphilis using the SHC^TM on finger-stick specimens; a venous blood sample was drawn concurrently and submitted for treponemal (EIA) and non-treponemal testing (RPR) at the state public health laboratory. The SHC^TM result was compared to the results of routine syphilis testing at the state laboratory. 

Results: The SHC^TM was used to screen 202 patients for syphilis. Of these, 171 (85%) were non-reactive on all syphilis tests (SHC^TM, EIA, RPR), 26 (13%) had a reactive SHC^TM, and 5 (2%) had a non-reactive SHC^TM but had one or more reactive tests at the state laboratory. Among the 26 reactive SHC^TM, 10 (38%) had a reactive EIA (5 with a reactive RPR), and 16 (62%) were not confirmed by EIA or RPR at the state laboratory. Among the 5 specimens that were SHC^TM non-reactive, only 1 was both RPR (1:8) and EIA reactive; it came from a patient with primary syphilis.

Conclusions: The high proportion of reactive SHC^TM tests not confirmed by reference treponemal testing suggests that reactive SHC^TM results should be interpreted with caution. Although only one false negative SHC^TM test result was identified, it is notable that the specimen was from a primary syphilis case-patient. Further evaluation is needed to determine if SHC^TM may be beneficial in identifying patients requiring follow-up syphilis testing, especially when phlebotomy is unavailable.