Literature review > Issue_5 > Review on Wendel et al. 

In the era of nucleic acid amplification tests (NAAT) for detection of sexually transmitted pathogens such as T. vaginalis for which culture is insensitive, the clinical and epidemiological significance of culture-negative, NAAT-positive infections remain poorly understood. In this report, Wendel and colleagues describe the relationship between T. vaginalis detected by urine culture and PCR and clinical features of infection in men attending an urban US STD clinic. Culture-proven T. vaginalis infections were associated with older age (> 28 years) and urethritis (> 4 PMN/hpf), however these associations were not evident when trichomoniasis was defined by a positive culture or confirmed PCR. These associations are consistent with the notion that culture detects infections with higher organism burdens compared to PCR, and these higher parasite loads contribute to increased inflammation in older men.

There are several limitations of the study acknowledged by the authors, including the variable volumes of urine used in the retrospective application of PCR. In our experience, the sensitivity of T. vaginalis PCR is severely compromised when whole urine is frozen before preparation of template DNA; as few as 50% of urines that are positive when tested fresh remain positive after storage at -70C for 3 months or longer (unpublished observations). In addition, culture-positive T. vaginalis infections in men are likely missed when a single specimen is tested. In a recent report that appeared after the paper by Wendel et al., when T. vaginalis was cultured from urine, urethral swabs and semen, the number of cases increased by 31% [1]. Recent observations using PCR to detect T. vaginalis in the male partners of infected women suggest that testing multiple specimens results in a similar increase in infections identified by NAAT (manuscript in preparation). It will be important to determine whether the associations identified by Wendel et al. for trichomoniasis in men defined by culture, but not PCR and culture, can be confirmed using multiple specimens in prospective studies that do not rely on frozen specimens.

References:

1. Kaydos-Daniels, S. C., W. C. Miller, I. Hoffman, M. A. Price, F. Martinson, D. Chilongozi, D. Namakwha, S. Gama, S. Phakati, M. S. Cohen, and M. M. Hobbs. 2004. Detection of Trichomonas vaginalis infection from various genitourinary sites in men. J Infect Dis 189:1926-1939.

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