Diagnosis of syphilitic genital ulcer- the quest for a reliable laboratory method

Objectives: Dark field microscopy (DFM), once performed widely as a reliable method of diagnosing Syphilis, is rapidly losing ground to newer serological tests and molecular methods, including PCR. This study aimed at tracing the performance of Dark Field Microscopy over the years and evaluating its usefulness in the present scenario. Also, doubts have been raised about the accuracy of the routinely used Syphilis non-specific screening tests such as VDRL and RPR, especially in populations with a high prevalence of HIV and malaria. The perils of untreated syphilis include dire consequences of latent or tertiary stages as well as transmission of infection from mother to foetus, with resultant congenital syphilis. An analysis of available diagnostic tests for syphilis was carried out to evaluate the performance of each method and assess its usefulness in providing an accurate diagnosis. Methods: This study was part of an operational research project which involved analysis of data of one year, during which dark field microscopy was performed for genital ulcer disease, along with other serological tests like VDRL, TPHA and FTA-Abs, for the diagnosis of Syphilis. Results: Of the 100 cases of genital ulcer diseases recruited in the study, over a period of one year, 7 were clinically diagnosed as Syphilis alone, while 4 were diagnosed as mixed infections of Syphilis along with Chancroid or Herpetic ulcer. The rest were clinically diagnosed cases of Herpes genitalis alone (78) or mixed infections of chancroid and herpes genitalis. From the study it was evident that DFM had poor sensitivity (33.3%), with clinical diagnosis having 85% sensitivity. All other diagnostic methods, including VDRL, TPHA, FTA-Abs and ELISA-Tp, had 100% sensitivity and specificity. Conclusion: With the advent of HIV infection, GUDs with two or more causative organisms are common, making aetiological diagnosis difficult without sophisticated laboratory tests. Serological tests for syphilis are simple to perform, but are only useful when the infection is not very recent. Treponema pallidum PCR, while more informative early in infection, is not available widely in developing countries, due to cost constraints. From the present study, it can be concluded that both non-specific and specific tests for diagnosis of Syphilis are reliable and can continue to be used for diagnosis, especially in resource poor settings where other diagnostic tests may be unavailable. Clinical diagnosis needs to be backed by laboratory methods to improve the accuracy, and institute appropriate treatment. Dark field microscopy, although not very sensitive, should continue to be used, as it is highly specific and offers an immediate diagnosis, which will be of immense value to the clinician and patient for early and appropriate treatment.