Bacterial Vaginosis (BV) is a common condition resulting from an imbalance in the vaginal microbiota, involving the overgrowth of anaerobic bacteria and a reduction in protective Lactobacilli species. White blood cells (WBCs), or leukocytes, are immune cells that increase when the body is fighting infection or inflammation. The relationship between BV and WBC levels is often misunderstood because BV’s effect on the immune system differs from most other infections, making clarification important for correctly interpreting diagnostic results.
Understanding Bacterial Vaginosis
Bacterial Vaginosis is characterized as a polymicrobial shift involving the decrease of hydrogen peroxide-producing Lactobacilli, which normally maintain a low, acidic pH. This reduction allows for the proliferation of anaerobic organisms, such as Gardnerella vaginalis and Atopobium vaginae, raising the vaginal pH above its normal acidic range, typically past 4.5.
Common symptoms include a thin, gray or white vaginal discharge and a distinct “fishy” odor, often stronger after intercourse. Significantly, BV is classified clinically as a non-inflammatory condition, a defining characteristic that distinguishes it from other forms of vaginitis.
White Blood Cells and Immune Response
White blood cells are the body’s cellular defense system, mobilized to combat foreign invaders and signal tissue damage. When inflammation or infection occurs, these cells travel to the affected site to neutralize threats. Measuring the WBC count is a standard method for assessing the severity of the immune response.
WBC counts are measured systemically via a blood test, where a high result (leukocytosis) indicates body-wide immune activation. Alternatively, a local WBC count is measured by examining a fluid sample, such as vaginal discharge, reflecting inflammatory activity specifically in that localized tissue. A high local count signals a strong inflammatory reaction at the site of infection.
BV’s Effect on WBC Levels
Bacterial Vaginosis typically does not cause a high systemic WBC count because the condition is localized and does not trigger a widespread immune reaction. Crucially, BV usually does not cause a high local WBC count in the vaginal fluid, as its minimal inflammatory nature means the body does not send a heavy infiltration of leukocytes.
The lack of a significant local WBC count helps differentiate BV from other infections. Diagnostic criteria, such as the Amsel criteria, focus on factors like pH, “clue cells,” and discharge characteristics, not inflammation markers. If WBCs are present microscopically during a BV diagnosis, they are usually few and scattered, unlike the dense accumulation seen in true inflammatory conditions.
The absence of a pronounced WBC response helps distinguish BV from infectious vaginitis, which is characterized by significant inflammation. If a high number of WBCs is observed alongside signs of BV, it strongly suggests the presence of an additional inflammatory vaginal or cervical co-infection. Therefore, a high WBC count points away from BV as the sole problem.
Other Causes of Elevated Vaginal White Blood Cells
Since isolated BV does not significantly raise the local WBC count, the presence of numerous leukocytes in a vaginal fluid sample indicates an inflammatory process is occurring. If a patient presents with symptoms suggesting BV but lab work shows a high local WBC count, the diagnosis is likely a true inflammatory infection, such as vaginitis or cervicitis.
Conditions that commonly trigger a robust inflammatory response and a high local WBC count include certain sexually transmitted infections (STIs). These include Trichomonas vaginalis (trichomoniasis), Chlamydia trachomatis, and Neisseria gonorrhoeae. Pelvic inflammatory disease (PID), an infection of the upper reproductive tract, also causes significant inflammation and elevated WBC levels. Detecting a high number of WBCs signals the need to test for these other inflammatory conditions.