Syphilis and blood donors: Comparison of two different diagnostic strategies

In this study the validity of the methods provided for by Italian law (VDRL or RPR tests) were compared with the diagnostic strategy suggested by WHO (the use of VDRL and TPHA tests in parallel). Sensitivity, specificity and posterior probability of infection after a positive or a negative result were estimated. The application of two tests in parallel produces a statistically significant increase of sensitivity from 47% to 98% while the increase of proportion of false positives is not significant (from 15% to 16%). Probability of infection when the result is negative to the RPR is 0.07%o while a negative result to the RPR and the TPHA tests has a probability to be really infected of 0.003%o. The use of the two tests (RPR and TPHA) in parallel is able to give the highest degree of sensitivity, indispensable to select possible blood donors, while maintaining a good degree of specificity. The authors concluded that the use of VDRL alone does not exclude infectivity of a blood sample, and in accordance with WHO and international recommendations, the VDRL or RPR and TPHA tests should be used in parallel for syphilis screening.     

不同检验方法对梅毒不同时期的敏感性和特异性分析

目的对比研究3种不同的梅毒临床检测方法的敏感性和特异性,从而筛选敏感性和特异性较高的诊断方法。方法采用梅毒螺旋体血球凝集试验(TPHA)、梅毒螺旋体明胶颗粒凝集试验(TPPA)和酶联免疫吸附试验(ELISA)检测75例梅毒患者和55例非梅毒患者。结果 3种检测方法 TPHA、TPPA、ELISA的临床敏感性分别为:91.2%、97.8%、98.7%,特异性分别为:96.3%、98.5%、98.2%。TPPA的敏感性和特异性均较好,与其他3种方法相比,ELISA检测方法的敏感性和特异性也较好,与TPPA比较均无统计学意义(P0.05);TPHA临床敏感性稍差,与TPPA比较有统计学意义(P0.05),其特异性尚好,与TPPA比较无统计学意义(P0.05)。结论 TPPA、ELISA均为临床较好的梅毒诊断检测方法。