Vaginal pH is similar to follicle-stimulating hormone for menopause diagnosis
S. Roy MSPH.C. Caillouette T. Roy MSPHJ.S. Faden PhD
Department of Obstetrics and Gynecology, Keck School of Medicine of the University of Southern California, Women's and Children's Hospital, Los Angeles, Calif; Bethel, Conn; Food and Drug Administration, Washington, DC USA 

Study design
Sixteen studies regarding vaginal pH and menopausal symptoms before and after estrogen administration were analyzed. Two epidemiologic studies that reported follicle-stimulating hormone or vaginal pH with menopause were reviewed. These findings were compared with similar data from the practice of one of the authors (J.C.C.).

Results
Menopausal women who do not receive estrogen therapy have a weighted average vaginal pH of 6.0, which is reduced significantly to 4.5 with estrogen therapy. To diagnose menopause, follicle-stimulating hormone 15 or 20 mIU/mL in the Third National Health and Nutrition Examination Survey had a sensitivity of 65% to 68%. In a study in Costa Rica, where 3 definitions of menopause were used, a pH of >5.0 had a sensitivity of 64% to 67%. From the practice patients, the 95% confidence interval sensitivities and positive predictive values of vaginal pH and follicle-stimulating hormone to diagnose menopause overlapped, while a pH £4.5 indicated mid follicular phase estradiol levels.

Conclusion
In women without vaginitis and no estrogen therapy, a vaginal pH of >4.5 indicates menopause, because it demonstrates a similar sensitivity as follicle-stimulating hormone in epidemiologic studies. In the practice patients, the sensitivity of follicle-stimulating hormone was no different than vaginal pH in the diagnosis of menopause. Furthermore, with estrogen therapy, a vaginal pH of £4.5 indicates a mid follicular phase estradiol.


Early studies demonstrated that, without vaginal infections, vaginal pH was £4.5 during the reproductive years and >4.5 before menarche and after menopause.[ 1 ] Before the vaginal pH device[ 2 ] became available in 1996, obtaining vaginal pH required pressing a strip of pH paper against the vaginal wall (holding it with either the fingers or a forceps) or placing it in vaginal pool secretions from the posterior fornix.[ 3 ] However, contamination with cervical mucus, blood, or semen may occur, which results in an incorrect vaginal pH reading[ 3 ](generally >6.0). To permit a vaginal pH reading to be obtained easily and correctly from the lateral outer third of the vagina by a health care provider or patient, a specific calibration of Nitrazine Paper (Bristol-Myers Squibb Company, Princeton, NJ) was selected and mounted at the end of a small disposable plastic device. After 5 seconds of vaginal contact, the color of the paper is compared with a colorimetric scale on an enclosed card, and the pH value is determined. This device, pHEM-ALERT®, developed by FemTek LLC, is distributed by GYNEX (Redmond, Wash).

The normal vaginal wall pH of a reproductive-aged woman is 3.8 to 4.5.[ 4 ] An interrelationship exists between sufficient vaginal estrogen and the vaginal microflora and their metabolic products.[ 4,  5 ] Estrogen proliferates vaginal epithelium.[ 6,  7 ] In response to estrogen, the glycogen content within vaginal cells is increased and released into the vagina,[ 8 ] which supports the growth of various strains of hydrogen peroxide and lactic acid that produces lactobacillae, generates an acidic pH, and maintains vaginal health.[ 5 ] The resulting vaginal microflora comprises numerous micro-organisms that include Gram-positive and Gram-negative aerobic, facultative, and obligate anaerobic bacteria.[ 5,  9 ]

In the presence of vaginitis, an elevated vaginal pH > 4.5, may indicate various conditions (such as bacterial vaginosis, trichomonas vaginalis, group B streptococcus, or other pathogenic organisms).[ 10 ] In the absence of vaginitis, an elevated vaginal pH may reflect low circulating estrogen levels (estradiol, <40 pg/mL) or inadequate response of atrophic vaginal epithelium to ERT.[ 11 ] However, like an elevated temperature, an elevated pH alone is only presumptive and not diagnostic. A diagnosis of the underlying condition or cause of the elevated pH should be established by obtaining additional history, eliciting symptoms and signs, and performing tests.

Increasingly, health care providers determine vaginal pH routinely as part of well-woman examinations and for diagnostic purposes in patients with symptoms of vaginitis[ 12,  13 ] or for the request of hormone therapy.[ 10,  14 ]

The purpose of this study was to determine whether vaginal pH value is associated with menopausal status and symptoms, to review the sensitivity of follicle-stimulating hormone (FSH) or vaginal pH values in diagnosing menopause, to compare these findings to a group of practice patients, and to determine whether vaginal pH values could be used in place of FSH as an initial screen to determine menopause.


1. Material and methods
Sixteen studies that reported vaginal pH before and after ERT in patients who were symptomatic for genitourinary complaints were selected from the literature.[ 14,  15,  16,  17,  18,  19,  20,  21,  22,  23,  24,  25,  26,  27,  28,  29 ] These studies were analyzed to indicate the numbers of individuals and their vaginal pH values before and after ERT.

As reported in the Third National Health and Nutrition Examination Survey (NHANES III) study,[ 30 ] the traditional test to diagnose menopause is FSH. A large epidemiologic study, conducted by the National Institutes of Health in Costa Rica, in which vaginal pH was reported as a function of aging and menopausal status, was reanalyzed.[ 31 ] In this study, after the insertion of an unlubricated speculum, vaginal pH was obtained by placing a pHydrion strip (Micro Essential Laboratories, Brooklyn, NY) on the lateral vaginal wall until it became wet. Color change of the strip was compared immediately with a colorimetric scale that indicates vaginal pH, and the measurement was recorded.

One of the authors (J.C.C.) identified 309 menopausal patients (eg, no periods in 12 months, FSH >22.9 mIU/mL or estradiol <40 pg/mL, whose vaginal pH, as determined by pHEM-ALERT, and FSH had not previously been correlated and reported).[ 10 ] The data, including presence or absence of hormone therapy, are noted as related to vaginal pH and estradiol, to further expand the previous report.[ 10 ] Body mass index was calculated and correlated with the findings.

To permit calculation of sensitivity, specificity, and positive and negative predictive values as defined in - Table: [ 1], the data were placed onto 2 × 2 tables in the traditional manner. The 95% CIs of rates, t-test, and Fisher exact test were performed with SAS software (version 8.01, PROC FREQ and Proc-StatXact 4; SAS Institute Inc, Cary, NC).

   
2. Results
The weighted average of vaginal pH values was calculated from the literature ( - Table: [ 2]). Menopausal women who were not receiving estrogen replacement therapy (ERT) had a vaginal pH value of 6.0, which was reduced significantly to 4.5 with ERT.


A total of 3388 women who were aged 35 to 60 years were examined during the personal interview that was associated with the NHANES III. When women who were receiving ERT were excluded from the analysis, 65% of the women with serum FSH of ³15 IU/L and 68% of the women with serum FSH of ³20 IU/L were menopausal.

In contrast to FSH, the epidemiologic study that was conducted in Costa Rica involved 9161 patients and examined the association of vaginal pH with age and menopausal status. - Table: [ 3] presents self-declared menopause, absence of menstrual cycles, and age >50 years as they relate to vaginal pH value. All 3 categories had a sensitivity to diagnose menopause of 64% to 67%.  

In practice patients, the association of vaginal pH with FSH, according to estradiol values, is shown in - Table: [ 4]. This presents the test performance for estradiol values as they relate to vaginal pH off and on ERT and FSH at the 2 cut-off values, as used in NHANES III. - Table: [ 4] indicates that the 95% CI sensitivities and positive predictive values of vaginal pH and the 2 FSH cut-off values overlap. Indeed, vaginal pH of >4.5 and FSH of ³15 mIU/mL or ³20 mIU/mL are highly associated, with the use of the Fisher exact test that compares the categories ( P<.001). Therefore, they are similar in their ability to diagnose an estradiol value of <40 pg/mL, which is one of the markers for menopause.
  

The average estradiol value ± SEM for those patients who receive no ERT with a pH value of >4.5 and an estradiol value of <40 pg/mL (n = 89 patients) was 15.0 ± 0.9 pg/mL; for those patients who did receive ERT with a pH value of £4.5 and an estradiol value of ³40 pg/mL (n = 105 patients), the average estradiol value was 128.6 ± 9.3 pg/mL.

BMI was not correlated with any of the analyses.

3. Comment
Since the advent of the radioimmunoassay for estradiol, vaginal pH has been neglected, despite a long history for indicating a vaginal response to estrogen.[ 1,  7,  32 ] Vaginal pH is an inexpensive, easy, rapid way to determine vaginal estrogen status. In the presence of vaginitis, studies support the use of vaginal pH as an aid to determine therapy.[ 33 ] If the pH is £4.5, the use of over-the-counter antifungal medication may be considered initially. If the pH is >4.5, the patient should seek medical care.[ 33 ]

In the absence of vaginitis, vaginal pH is a suitable alternative to determine whether a patient is menopausal. The reviewed literature ( - Table: [ 2]) indicates that symptomatic menopausal patients who are not receiving ERT have an elevated vaginal pH that coincides with the resolution of their symptoms and significantly reverts to premenopausal levels after ERT. In most menopausal patients who receive ERT, a vaginal pH of >4.5 indicates low circulating estradiol levels, which suggests the need for an adjustment of dose or route of hormone therapy.[ 10 ] However, some patients with vaginal atrophy do not replenish their vaginal epithelium, while receiving oral therapy, despite suitable circulating estradiol levels.[ 34 ] For them, augmenting oral therapy with topical vaginal estrogen may be necessary.[ 14 ] Atrophic vaginal epithelium permits greater absorption of estrogen as compared with well-estrogenized epitheliem.[ 32 ]

The epidemiologic studies that were reviewed indicate that serum FSH and vaginal pH have a similar sensitivity in the identification of menopausal patients. The large study conducted in Costa Rica did not obtain laboratory confirmation of menopause with either FSH or estradiol level. The ingestion of herbal medicaments was not reported. Although sexual activity (coital activity ³3 times per month) and douching (with water and vinegar) were associated with lower vaginal pH measurements, the interval between sexual activity, douching, and vaginal pH measurement was not noted. Despite these factors, the Costa Rica study indicated self-reported menopause that was associated with obtaining a vaginal pH of ³5.0 in a similar percent of subjects as did serum FSH in the NHANES III study, which was conducted with stratified sampling that was designed to capture the diversity of the US population. The FSH values from the practice patients are considerably more predictive of menopause than the rate that was reported in the NHANES III study, but the study numbers were small and may not have reflected the experience in a more general population. However, in the practice patients, the sensitivity 95% CIs for the 2 FSH values that were reported in the NHANES III study overlapped those of vaginal pH >4.5, which demonstrates significant association with estradiol of <40 pg/mL that signifies menopause, and indicates that vaginal pH is similar to FSH in the diagnosing of menopause.

Menopausal women who were not receiving ERT and who had a vaginal pH value of >4.5 had low estradiol values, and those women who were receiving ERT and who had a vaginal pH value of £4.5 had estradiol in the mid follicular range, which indicated that vaginal pH reflects circulating estradiol. Therefore, with the use of vaginal pH, it is possible to monitor the slow introduction or adjustment of the dose, route, or schedule of estrogen administration to achieve a satisfactory vaginal pH response, while simultaneously resolving somatic symptoms (eg, hot flashes, vaginal dryness).[ 10,  14 ] This study further supports the monitoring of estrogen administration by the use of a vaginal pH value of £4.5, which indicates a circulating estradiol value of >40 pg/mL.[ 10 ] Because most practice patients were similar in body habitus, it is not surprising that body mass index was not correlated with the vaginal pH or estradiol values. In other settings, body mass index may influence vaginal pH and estradiol values.

In summary, this study confirms that vaginal pH is similar to FSH in the identification of patients who have low estrogen levels or who are menopausal. Also, a vaginal pH value of £4.5, unlike FSH, can be used to monitor ERT on an individual-patient basis to indicate an estradiol level of >40 pg/mL. Such monitoring of patients should be considered in subsequent epidemiologic studies instead of the inappropriate use of a single drug, dose, and route of therapy, as was used in the Women's Health Initiative Study.[ 10,  35 ]


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