Comparison between vaginal swab and endocervical swab during pelvic examination

While wet mounts and potassium hydroxide (KOH) preparations are frequently used to help diagnose vaginitis and cervicitis, the sample site varies. This study was conducted to evaluate whether the specimen site (vaginal pool versus endocervical specimen) affects diagnostic sensitivity.

The study involved 116 consecutive adolescent females presenting to a medical clinic serving high-risk youth. During the pelvic examination, specimens were obtained from the endocervix and the vagina (posterior fornix and sidewall) and placed in separate tubes of normal saline. Each specimen was examined for trichomonads, white blood cells, pseudohyphae, clue cells, and amine odor using 10% potassium hydroxide.

The sensitivity was highest for the vaginal specimen in detecting the presence of trichomonads (100% versus 50%), pseudohyphae (76% versus 65%), and clue cells (95% versus 50%). For those with symptomatic candida vaginitis (n = 12), there was no difference in sensitivity (83%) between the two methods for detecting pseudohyphae. Nineteen of the adolescents had a diagnosis of cervicitis (chlamydia by DFA, gonorrhea by culture, and trichomonas by wet mount). If > 5 white blood cells/high powered field (WBC/HPF) was used as a criterion for the presence of a cervicitis, the vaginal sample had a sensitivity of 79% (15/19) and a specificity of 67%, while the endocervical sample had a 74% sensitivity (14/19) and a 57% specificity.

A wet mount obtained from either the vaginal pool or endocervix is not highly specific for diagnosing a vaginitis or cervicitis. However, obtaining a specimen for wet mount and KOH swab from the vaginal pool is more sensitive for detecting trichomonads, pseudohyphae, or clue cells than an endocervical swab.