Vol. 17 • Issue 10 • Page 29
Vaginal pH has the highest sensitivity of any criterion for the diagnosis of vaginitis, a condition seen daily by nurse practitioners in primary care and women's health settings. A diagnostic algorithm based on vaginal pH can be helpful and cost effective for accurate categorization of the cause of vaginal symptoms. Self-obtained vaginal pH measurement is a simple, inexpensive way for women to assess vaginal symptoms and decide whether to see a provider or to self-medicate.
Importance of Vaginal pH
Normal vaginal flora is characterized by a dynamic balance between lactobacilli and potential vaginal pathogens. When the equilibrium of the vaginal flora is altered, lactobacilli are diminished and a concomitant decrease in acidity occurs, allowing organisms normally suppressed by lactobacilli to proliferate.1The measurement of vaginal pH determines the status of the vaginal ecosystem. In terms of vaginal ecology, an acidic (3.5 to 4.5) pH is maintained by Lactobacillus species that secrete lactic acid along with hydrogen peroxide. Stimulated by estrogen, the vaginal epithelial cells of reproductive-age women produce glycogen, which encourages growth of lactobacilli, thus increasing lactic acid production and maintaining vaginal pH (less than 4.7).2
Normal pH is a marker of adequate amounts of vaginal lactobacilli.2A more alkaline vaginal milieu leads to the depletion of lactobacilli, with concomitant proliferation of pathogenic organisms.3Elevated vaginal pH is associated with a loss of lactobacilli, especially strains that produce hydrogen peroxide. Vaginal pH is elevated during menses, during hormonal shifts and following intercourse. It can also be increased by douching. Elevated vaginal pH enhances the growth of organisms that contribute to bacterial vaginosis and Trichomonas growth.4An inverse relationship exists between the loss of lactobacilli and increased vaginal pH. This balance in the vaginal ecosystem is maintained by a variety of interrelated endogenous and exogenous factors. Which is the cause and which is the consequence is not understood in every situation.
Overview of Vaginitis
The three most common vaginal infections are bacterial vaginosis (BV) in 22% to 50% of vaginitis cases, vulvovaginal candidiasis (VVC) in 17% to 39% and trichomoniasis in 4% to 35%.4At least 70% of women experience at least one episode of candidiasis.5The most common complaints associated with vaginitis are itching, odor, increased discharge, burning, irritation, dyspareunia, dysuria or some combination of these. Although the most common forms of vaginitis are BV, trichomoniasis and candidiasis, more causes exist, many of them noninfectious.2The most common causes are listed in Table 1.
Some types of vaginitis can no longer be regarded as trivial, because research and clinical experience have identified adverse health consequences. BV and trichomoniasis have been associated with acquisition of other sexually transmitted infections (including HIV), as well as with adverse pregnancy outcomes and complications after gynecologic surgery.6
Office Diagnosis
The diagnosis of vaginitis relies on the results of clinical examination and diagnostic testing. Two factors make these tasks challenging: Office-based tools offer varying degrees of accuracy and time to results, and according to the Centers for Disease Control and Prevention, up to half of women with BV are asymptomatic.
Proper diagnosis requires evaluation of the characteristics of vaginal discharge: consistency, color, amount, odor, pH and microscopic findings. Many symptoms and signs of BV and trichomoniasis infections overlap.6Even in the best of hands, office-based tests for vaginitis can have low sensitivity: 92% for BV (Amsel's criteria), 62% for trichomoniasis (saline wet mount preparation) and a mere 22% for candidiasis when using KOH wet mount for fungal organisms.7A recent study of 485 women sought to examine the agreement between telephone and office management of vulvovaginal complaints.8The study involved prospective, structured telephone interviews of all patients with vulvovaginal complaints who called the Kaiser Permanente Telephone Call Center during the study period. Nurses performed the phone interviews. Patients then saw a physician, nurse midwife or physician assistant for office evaluation. Each group made independent diagnosis and treatment decisions. Kappa coefficients were used to evaluate interexaminer agreement between the nurses who conducted the phone interviews and the providers who administered traditional diagnostic tests. A diagnosis of vaginal symptoms based on a telephone triage system correlated poorly with actual clinical diagnosis.8
Self-Diagnosis
The self-diagnosis and self-treatment of VVC are fraught with error. Since the approval of topical antifungal agents as OTC medications, women have grown increasingly dependent on self-diagnosis and treatment.2But frequent misuse of OTC products occurs. One study found that symptomatic women who purchased OTC antifungals for treatment of vaginitis did not have candidiasis, and many repeated dosing up to three times.9
This study also examined whether consumers who read the package inserts of OTC antifungals make better decisions about therapy than those who don't. The researchers did not find any improvement in patients' ability to properly diagnose VVC after reading the package insert.9i> Approximately two-thirds of women who purchased OTC antifungals for presumed VVC did not have candidiasis. Women who previously had a diagnosis of VVC and those who read the package inserts for OTC antifungals were no more likely to have VVC than women who had not had previous episodes or who did not read the insert.9
To more accurately categorize the cause of a woman's vaginal symptoms and improve self-diagnosis, a diagnostic algorithm based on vaginal pH has been proposed.2With self-testing for vaginal pH, as much as 50% of inappropriate antifungal use in symptomatic women could be avoided.10
Vaginal pH as a Diagnostic Tool
A vaginal pH greater than 4.5 in combination with vaginal symptoms effectively rules out a diagnosis of bacterial vaginal candidiasis, suggesting a diagnosis of BV or trichomoniasis. But healthcare providers infrequently perform vaginal pH testing.11
When pH testing is performed, it can be valuable in making a proper diagnosis. A study of 288 symptomatic women evaluated various diagnostic measures for the determination of BV (Amsel's composite criteria and individual criteria, Gram's stain and a point-of-care test); pH was the most sensitive of the individual criteria (96%), with a specificity of 78%.12In an observational study, 269 women undergoing vaginal exams were evaluated for BV using all four Amsel's criteria, along with Gram's stain evaluation.13The researchers evaluated the sensitivity and specificity of each criterion, as well as combinations of criteria. For the diagnosis of BV, the sensitivity of vaginal pH was 89% and the specificity was 74%.12,13In addition to being a sensitive diagnostic tool for vaginitis, vaginal pH testing is cost effective. This is illustrated in a published cost effectiveness model for the diagnostic workup of vaginitis.14The model assumes the possible etiologies of vaginitis are yeast, BV or trichomoniasis. Cervicitis can also mimic vaginitis, so chlamydia and gonorrhea were also considered as possible causes, as was herpes infection, which can present similarly to vaginitis.14This analysis points to the value of vaginal pH as a simple, inexpensive screening tool to guide vaginitis diagnosis. Adding pH-guided empiric therapy to any of the testing strategies shortened symptom duration and decreased overall cost. Testing for all diagnostic possibilities of vaginitis - except for BV and trichomoniasis when the pH was normal - was the least expensive diagnostic strategy.14A pH-based framework to identify the most common causes of vaginitis has been proposed (see figure, next page).1Based on pH findings alone, women can be classified by those with normal or elevated vaginal pH and further classified based on whether their vaginitis is due to infectious or noninfectious causes. As illustrated in the figure, many cases of vaginitis may be due to noninfectious causes, some of which are in fact normal (e.g., presence of menstrual blood, semen following intercourse, ovulatory cervical mucus).
A chart review of 203 consecutive cases evaluated for vaginitis by wet mount microscopy examined the relationship between vaginal pH, symptoms and microscopy findings.15Elevated vaginal pH was significantly associated with BV alone (p < 0.001), trichomoniasis alone (p < 0.01) and mixed infections of BV and trichomoniasis (p < 0.003).15 ormal pH was significantly associated with negative microscopy (p < 0.001) and weakly associated with candidiasis alone (p < 0.06).15i> Among symptomatic patients, elevated vaginal pH was significantly associated with clue cells (BV), Trichomonas infection and mixed infections. Normal pH was associated with negative (normal) wet mount findings when no pruritus was present (Table 2).
Ninety-seven percent of the 118 symptomatic women with BV alone, trichomoniasis alone or mixed infection had vaginal pH greater than 4.5, compared with only 3% of women with Candida alone. Elevated pH provided 99% sensitivity for BV, trichomoniasis or both on wet mount. When focusing solely on asymptomatic patients (n = 85), researchers identified a strong association of elevated pH with positive wet mount findings of BV, trichomoniasis or mixed infection with both. Routine pH testing detected a significant number of asymptomatic infections as well, providing an opportunity for treatment and counseling of infected patients.15
Patient Acceptance
Women have demonstrated a high degree of acceptability and ability to self-swab the vagina for pH determination, achieving substantial agreement with physician-obtained pH readings.16In a study of 129 pregnant women, self-collected vaginal swabs were compared with physician-collected smears using pH findings and Gram's stain in the diagnosis of bacterial vaginosis. Researchers documented substantial agreement (kappa = 0.82) between the two techniques in diagnosing BV.16
With respect to vaginal pH testing alone, another researcher found that women with symptomatic vaginitis could correctly use a self-test pH device and achieve the same results as healthcare providers performing vaginal pH testing.10
Women received a vaginal pH self-test device, a package insert and a questionnaire. Eighty-eight symptomatic women self-collected vaginal pH specimens and then underwent the same test with their healthcare providers (Table 3). The study documented high correlation between a patient reading of elevated pH (greater than 4.5) and a clinical diagnosis of bacterial vaginosis or trichomoniasis.
A follow-up study sought to confirm that women could read and understand the package insert for a vaginal pH test kit.17It followed 206 women of different ethnicities, education levels and ages (17 to 61) in eight clinic locations. The researchers provided a package insert explaining the indications and use of a vaginal pH test, along with a 16-item questionnaire to assess comprehension. Nearly 80% of women either answered all questions correctly or had only one error. The authors concluded that self-testing would lead to improvement in decisions to use OTC antifungal medications or seek care from a healthcare provider.17Similar results were obtained in a more recent study of patients older than 18. Each received a self-test for vaginal pH along with a one-page instruction sheet describing the technique for self-measurement of vaginal pH, along with a pH color chart to determine vaginal pH value. Healthcare providers independently determined the patient's vaginal pH results, to evaluate concordance of findings. The researchers noted minor but clinically insignificant differences in vaginal pH determinations.3A recent study similarly sought to determine if women could accurately measure their vaginal pH compared with a physician measurement.5Nonpregnant women presenting to an academic ambulatory gynecology clinic were asked to perform self-swabs of vaginal secretions, apply the swab to pH paper, and compare it to a color chart for pH determination. Their findings were compared with the physician evaluations. One hundred thirty-four women (ages 18 to 85) completed the study. Overall agreement between the patient-obtained and physician-obtained vaginal pH was high (85%). Results did not differ significantly by age.5
OTC Vaginal pH Tools
The ease of use of self-evaluation tools has been demonstrated in clinical trials.10,17This is even true in countries such as Uganda, where researchers provided 311 poor women with a handmade pH measuring pad to follow weekly changes in vaginal pH over 2 years. These women were able to self-measure vaginal pH.18
Measurement of vaginal pH with home testing kits is a viable way to differentiate between vaginal infections associated with candidiasis and those due to BV or trichomoniasis.10,19Because self-diagnosis of VVC based on symptoms alone is inaccurate at least 50% of the time, a need exists for a simple, rapid pH screening test for women. Self-testing could reduce inappropriate self-treatment by half.10
OTC vaginal pH screening devices are available and can help distinguish vaginal symptoms that require attention by a healthcare provider.20These OTC tests help women determine whether their symptoms may be due to a yeast infection or another infection that requires medical care.
One such test kit contains two trays. Each tray contains a plastic wand with attached pH paper, detailed patient instructions and an easy-to-read, color-coded pH guide. To use, the woman inserts the device into the vagina and touches it to the vaginal wall to moisten the pH paper. After she withdraws the wand, the woman can identify her vaginal pH level by comparing the color of the pH paper to the color on the pH guide. A pH value of 4.5 suggests that vaginal symptoms are due to candidiasis. If the pH reading is 5.0 or higher, vaginal symptoms are likely due to BV, trichomoniasis or a mixed infection, and office follow-up is necessary.
OTC vaginal pH screening kits are marketed under names such as Vagisil Screening Kit for Vaginal Infections and VI-SENSE. Each kit costs approximately $15 to $20.
Putting It Into Practice
Vaginitis is a common condition among reproductive-age women in the United States, and vaginal pH is the most sensitive criterion for its diagnosis. Clinical trials have demonstrated that patient self-measurement of vaginal pH is strikingly similar to vaginal pH measurement by healthcare providers, validating the utility of home test kits.
Susan Wysocki is a women's health nurse practitioner who is president and chief executive officer of the National Association of Nurse Practitioners in Women's Health. She is a recognized leader and spokesperson on women's health topics.
References
1. Donders GG, et al. Comparison of two types of dipsticks to measure vaginal pH in clinical practice. Euro J Obstet Gynecol Rep Biol. 2007;134(2):220-224.
2. Nyirjesy P, Sobel JD. Advances in diagnosing vaginitis: development of a new algorithm. Curr Infect Dis Report. 2005;7(16):458-462.
3. Ferris DG, et al. Variability of vaginal pH determination by patients and clinicians. J Am Board Fam Med. 2006;19(4):368-373.
4. Anderson MR, et al. Evaluation of vaginal complaints. JAMA. 2004;291(11):1368-1379.
5. Kulp J, et al. The accuracy of women performing vaginal pH self-testing. J Women's Health. 2008;17(4):523-526.
6. ACOG Committee on Practice Bulletin. Vaginitis. ACOG Practice Bulletin number 72. Obstet Gynecol. 2006;107(5):1195-1206.
7. Landers DV, et al. Predictive value of the clinical diagnosis of lower genital tract infection in women. Am J Obstet Gynecol. 2004;190(4):1004-1010.
8. Allen-Davis JT, et al. Assessment of vulvovaginal complaints; accuracy of telephone triage and in-office diagnosis. Obstet Gynecol. 2002;99(1):18-22.
9. Ferris DG, et al. Over the counter antifungal drug misuse associated with patient-diagnosed vulvovaginal candidiasis. Obstet Gynecol. 2002;99(3):419-425.
10. Roy S, et al. Improving appropriate use of antifungal medications: the role of an over-the-counter vaginal pH self-test device. Infect Dis Obstet Gynecol. 2003;11(4):209-216.
11. Wiesenfeld HC, Macio I. The infrequent use of office-based diagnostic tests for vaginitis. Am J Obstet Gynecol. 1999;181(1):39-41.
12. Bradshaw CS, et al. Evaluation of point-of-care test, BV Blue, and clinical diagnosis of laboratory criteria for diagnosis of bacterial vaginosis. J Clin Microbiol. 2005;43(3):1304-1308.
13. Gutman RE, et al. Evaluation of clinical methods for diagnosing bacterial vaginosis. Obstet Gynecol. 2005;105(3):551-556.
14. Carr PL, et al. "Shotgun" versus sequential testing. Cost-effectiveness of diagnostic strategies for vaginitis. J Gen Intern Med. 2005;20(9):793-799.
15. Pavletic AJ, et al. Experience with routine vaginal pH testing in a family practice setting. Infect Dis Obstet Gynecol. 2004;12(2):63-68.
16. Strauss RA, et al. Diagnosis of bacterial vaginosis from self-obtained vaginal swabs. Infect Dis Obstet Gynecol. 2005;13(1):31-35.
17. Roy S, et al. The role of an over-the-counter vaginal pH self-test device package insert: can subjects learn what the device is for and how to use it? Am J Obstet Gynecol 2005;192(6):1963-1969.
18. Willyard C. pH paper trumps expensive kits in measuring acidity. Nature Med. 2007;13(10):1128-1129.
19. Scolaro KL, et al. Devices for home evaluation of women's health concerns. Am J Health Syst Pharm. 2008;65(4):299-314.
20. Dunican K. OTC Product: Vagisil screening kit for vaginal infections. J Am Pharm Assoc. 2008;48(2):e33.
|