The Quality Evaluation of Syphilis Rapid Diagnostic Test Kits in Thailand

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Bhurit Songthananit
Titaporn Pootipinyowat
Supaporn Phumiamorn
Rossaphorn Kittiyaowamarn
Somkid Srisopha
Kringsak Chaiwong

Abstract

Syphilis is a sexually transmitted and blood born disease caused by Treponema pallidum (T. pallidum). Recently, the syphilis rapid diagnostic kit of which the concept is based on the principle of lateral flow immunochromatographic assay has been widely used in Thailand and is considered as high-risk group of medical devices. However, in Thailand, it has not been yet evaluated and established standard criteria for the afore-mentioned test kits by national regulatory authority. Therefore, this study aimed to evaluate the quality of these test kits sold in Thailand in 2019, both cartridge and tab kits, in order to assess and evaluate their sensitivity, specificity,
accuracy, predictive positive value and predictive negative value. The 400 samples, including positive and negative for syphilis, were diagnostically confirmed by automatic machine and characterized by the Treponemal pallidum particle agglutination (TPPA). To determine the nonspecificity, another set of 50 samples which were syphilis negative with other conditions were used. The results showed that all 10 evaluated brands of test kits had a sensitivity range between 78.0-100% (95% CI: 75.8-100%), a specificity range between 94.8-100% (95% CI: 92.6-100%), an accuracy range between 89.0-99.5% (95% CI: 86.8-100%) and a non-specificity range less than 10%. From this study, it was indicated that the sensitivity and specificity of all kits were greater than or equal to the VDRL/RPR method. However, all test kits were not passed for blood bank screening and donation as per the standard criteria of World Health Organization guidelines. Thus, it can be concluded that 10 brands of these evaluated rapid kits in Thailand can be used for preliminary screening in the laboratory while their results need further confirmation by additional standard methods.

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