Vaginal pH changes can alter genital tract inflammation and bacterial contents. Both factors may alter human papillomavirus (HPV) infections. Usually HPV infections are temporary and only a few are persistent, leading to increased risk of precancerous cervical lesions and cervical cancer. An acidic vaginal pH (below 7) and Lactobacilli bacteria are parts of the defense system for the vagina. A more alkaline pH (pH above 7) usually accompanies a vaginal infection.
In healthy women, Lactobacilli bacteria produce lactic acid which helps maintain the acidic environment. “A pH range of 4.0-4.5 is considered normal for pre-menopausal women.” This pH range is acidic and helps prevent infections of the urinary tract and the vagina.
The present study measured vaginal pH in a group of over 9,000 women, and Pap smears were done. Specimens were tested for HPV by a test called polymerase chain reaction. Vaginal pH was measured using pHydrion paper strips with a range of 3.0 to 5.5. An assay was done for Chlamydia trachomatis, which can cause pelvic infections.
The study results showed a significant relationship between vaginal pH and age. Most women under 45 years had a vaginal pH of 4.5. Half of the women 55 and older had a pH of at least 5.0. HPV was positive especially in the 25-34 year old group, with fewer positives among the older women. HPV was associated with vaginal pH in all age groups under 55 years, and a vaginal pH of 5.0 or over was found to increase the risk of HPV by 10-20%. Over 55 years, there was no association between vaginal pH and HPV risk.
Under age 25, women with a pH over 5.0 were more likely to have C. trachomatis infections. A more alkaline pH has been shown to be associated with C. trachomatis infections.
CONCLUSION: There is a positive association between increased vaginal pH and HPV infection, especially among pre-menopausal women. Vaginal pH increases with age normally. A healthy vaginal pH in women of reproductive age is below 4.5. Higher pH values can be seen with infection, and aging, and may be associated with persistent HPV.
NOTE: pH paper can be used to test for cervical pH, but should test to the 3.0 range.
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PMID: 22316377.
Summary #731.
