Diagnostic Approach to Vaginal Infections with Moderate Polymorphonuclear WBCs

Clinical Significance

The presence of WBCs on saline microscopy of vaginal secretions is one of the additional criteria that supports a diagnosis of PID according to CDC guidelines 1, 2
An increased number of white blood cells on wet saline preparation is considered an indication of infection 3
The American College of Obstetricians and Gynecologists and the CDC recommend that the finding of moderate PMNs should prompt further investigation for specific infections, as it has limited diagnostic specificity on its own 1

If the patient has uterine/adnexal tenderness or cervical motion tenderness along with moderate PMNs, consider PID diagnosis 1, 2
Additional supporting criteria for PID include:
- Oral temperature >101°F (>38.3°C) 1
- Abnormal cervical or vaginal mucopurulent discharge 1
- Elevated ESR or CRP 1

Check for other microscopic findings on wet mount:
- Clue cells (bacterial-covered epithelial cells) suggest bacterial vaginosis 3
- Moving flagellated trichomonads indicate trichomoniasis 3
- Hyphae or budding yeast indicate candidiasis 3

Vaginal pH testing (normal pH should be <4.5; elevated pH is seen with bacterial vaginosis and trichomoniasis) 3
Whiff test (fishy odor with potassium hydroxide indicates bacterial vaginosis) 3
Testing for N. gonorrhoeae and C. trachomatis 1, 2

If the cervical discharge appears normal and no white blood cells are found on wet prep, the diagnosis of PID is unlikely 1
Standard wet mount microscopy can miss trichomoniasis in 30-50% of cases; more sensitive testing methods include culture, nucleic acid probe, or PCR 3
The CDC recommends that empiric treatment should be started promptly when PID is suspected based on clinical findings 1, 2