Ignored trichomonal infestation diagnosed by Papanicolaou smear

To compare the occurrence of Trichomonas vaginalis as demonstrated by culture and by Papanicolaou (PAP) smears in a sexually transmitted disease (STD) clinic.

The largest out-patient venereological clinic in Denmark.

As the prevalence of trichomonal infestation has decreased considerable in recent years direct microscopy of vaginal wet mounts is no longer performed routinely. Instead the screening diagnostic procedure is based on culture. We have retrospectively collected data on culture-negative women with Trichomonas vaginalis organisms present in cervical smears, taken on a routine basis to exclude atypical cells, and compared with the clinical findings.

Since 1992 a total of 17 women were found to harbour Trichomonas vaginalis in cervical smear. A vaginal discharge was described in 10 women, six of whom had concomittant unspecific vaginitis. However, four women had unexplained vaginal discharge that could have been related to infestation with Trichomonas vaginalis. In addition one asymptomatic woman had a male partner with persistent urethritis.

The prevalence of trichomoniasis is underestimated in women attending the clinic if the diagnosis is based on culture alone. PAP smears may be helpful in demonstrating characteristic trichomonal organisms. In general we do not recommend the PAP smear be used to diagnose STDs. However the finding of trichomanal organisms in smears should prompt a repeated culture and direct microscopy of vaginal wet mount.