Comparison of Diagnostic Accuracy of PCR Targeting the 47-Kilodalton Protein Membrane Gene of Treponema pallidum and PCR Targeting the DNA Polymerase I Gene: Systematic Review and Meta-analysis

Abstract

ABSTRACT Treponema pallidum PCR ( Tp -PCR) testing now is recommended as a valid tool for the diagnosis of primary or secondary syphilis. The objectives were to systematically review and determine the optimal specific target gene to be used for Tp -PCR. Comparisons of the performance of the two main targets are tpp47 and polA genes were done using meta-analysis. Three electronic bibliographic databases, representing abstract books from five conferences specialized in infectious diseases from January 1990 to March 2015, were searched. Search keywords included (“syphilis” OR “ Treponema pallidum ” OR “neurosyphilis”) AND (“PCR” OR “PCR” OR “molecular amplification”). We included diagnostic studies assessing the performance of Tp -PCR targeting tpp47 ( tpp 47- Tp -PCR) or the polA gene ( polA-Tp -PCR) in ulcers from early syphilis. All studies were assessed against quality criteria using the QUADAS-2 tool. Of 37 studies identified, 62.2% were judged at low risk of bias or applicability. Most used the U.S. Centers for Disease Control and Prevention (CDC) case definitions for primary or secondary (early) syphilis (89.2%; n = 33); 15 (40.5%) used darkfield microscopy (DFM). We did not find differences in sensitivity and specificity between the two Tp -PCR methods in the subgroup of studies using adequate reference tests. Among studies using DFM as the reference test, sensitivities were 79.8% (95% confidence intervals [CI], 72.7 to 85.4%) and 71.4% (46.0 to 88.0%) for tpp47-Tp -PCR and polA-Tp -PCR ( P = 0.217), respectively; respective specificities were 95.3% (93.5 to 96.6%) and 93.7% (91.8 to 95.2%) ( P = 0.304). Our findings suggest that the two Tp -PCR methods have similar accuracy and could be used interchangeably.