Background In March of 2010 a large commercial lab performing STD testing in Arizona implemented the reverse algorithm for syphilis testing with the use of the syphilis treponemal enzyme immunoassay (EIA).

Methods Per the Arizona Department of Health Services (ADHS) Sexually Transmitted Disease Control Program protocol, manual review of positive syphilis lab results is performed by one epidemiologist. During May through October 2010, this epidemiologist recorded negative syphilis EIA results identified among reported syphilis cases with a prior history of positive treponemal tests (TP-PA, FTA-ABS).

Results From 6 May 2010 to 29 October 2010 78 syphilis EIA tests were reported as negative in individuals with a previously positive treponemal test. Fifty of these tests were completed among males and 28 among females. This discrepancy was brought to the attention of the reporting lab in May and again in October 2010. In November, a coordinated investigation between the reporting laboratory, the ADHS public health lab, and the ADHS Sexually Transmitted Disease Control Program (ADHS STDCP) was undertaken. This investigation resulted in the identification and correction in a specimen transfer procedure at the local laboratory level. All providers of patients with possible incorrect lab results completed during this time period were notified of the problem and advised to retest their patients, if indicated. The ADHS STDCP continues to monitor syphilis lab results for this particular error and has not identified any further discordant results since the corrections were implemented in November 2010.

Conclusions Discrepancies in syphilis EIA results have been reported from other regions. The detailed manual review of all reported syphilis lab results by an epidemiologist at the ADHS STDCP aided in the detection of this particular issue. Upon implementation of electronic lab reporting, this program and others, should continue routine, manual quality assurance checks of syphilis laboratory results. Such practices are imperative to ensure that these errors do not go undetected and that syphilis patients do not go undiagnosed.