Evaluation of test results of microbiology laboratories of North India for standard tests for syphilis under an external quality assurance scheme.

Test results of syphilis serology are critical due to inter- and intralaboratory variability. The accuracy of results is crucial in the control of the disease. This study was aimed to compare results of laboratories and performance of methods for syphilis serology. Results of Veneral Disease Reference Laboratory (VDRL) or rapid plasma reagin (RPR) tests of 25 microbiology laboratories were compared in six proficiency testing sentinel surveys. The performance of laboratories was compared with the results of a hypothetical average laboratory. Of the 141 participants, 104 (73.8%) responded. The inter-laboratory variability was exhibited by 62.2% of samples tested by VDRL and 58.7% by RPR test. Intralaboratory variability was observed in 46.7% samples. There was an insignificant improvement in proficiency testing (PT) performance over the years with a significant improvement in 2007. The common errors involved departure from testing protocols. Syphilis serology proficiency testing is needed in India for reliability in test results.