Literature review > Issue_5 > Review on West et al. 

Because bacterial vaginosis (BV) continues to be a disease without a known cause or an identified etiologic pathogen it continues to suffer from a testing conundrum [1]. Therapeutic effectiveness relies on accurate testing to identify patients who might benefit from therapy yet many physicians rely on syndromic diagnoses, which do not always correlate to laboratory findings. Thus, treatment based solely on symptoms will misdiagnose many women [2].

Typically, the diagnosis of BV requires speculum examination to inspect and collect vaginal discharge, which is evaluated using Amsel's clinical criteria [3]. For research, the scoring of the morphology and composition of the vaginal flora by Gram stain is considered widely to be the gold standard. Although difficult to perform, the Gram stain is the only diagnostic test available for BV that can be preserved and read by others. It has been shown to correlate overall to the Amsel criteria in experienced institutions [4,5]. Thus, an objective, easy-to-perform test would be helpful and in 1998, the Food and Drug Administration approved the FemExamÒ, a pH and Amines TestCard^TM (Litmus Concepts, San Diego, CA) as an aid to the evaluation of vaginal discharge. There are two windows on the card: the first detects abnormal vaginal pH (>4.7) and the second detects the presence of volatile amines greater than 0.50mM. It is technically easier to obtain a swab of vaginal discharge and apply it to the card test than to perform the procedures needed to establish Amsel or Nugent criteria. However, the card test is a colorimetric test and cannot be preserved, so it too depends on the present user's interpretation of the results. It appears the company has recognized this limitation and a newer design for the card test is being evaluated [6]. West et al. seek to evaluate the cost and performance of the original FemExam card relative to Gram stain and compare these characteristics to Amsel's clinical criteria.

West et al. describe a prospective observational study of 219 consecutive women presenting July to October of 2000 with vaginal discharge and/or itching to a single genitourinary clinic in The Gambia. Surprisingly, 90.9% or 199/219 of the women had a vaginal pH greater than 4.6 on clinical examination but only 155 of 219 or 70.8% were positive on the pH portion of the card test. Nonetheless, 59 of 219 or 26.9% of women had normal Gram stain scores or Lactobacillus populations, a result which is difficult to reconcile with the large proportion of women with abnormal pH. The prevalence of BV by Gram stain (Nugent score of 7 - 10) was 47.9% - an estimate that likely reflects the select symptomatic GU clinic population studied.

Compared to Gram stain, the authors report sensitivity/specificity of 71%/73% for the FemExam card 1 and 91%/62% when a second card that tested for Gardnerella was included. It is not surprising that inclusion of the second card test for the presence of Gardnerella increases sensitivity at the expense of specificity since many women have Gardnerella and do not have clinical bacterial vaginosis. In addition, the results for the second card are suspect because of operational problems described by the authors.

The authors are correct in stating that "a good, reasonably priced, objective, easy-to-use rapid diagnostic kit would be a big asset" but the card test studied is not yet proven to be ready for prime time. The authors quote a reference with a sensitivity of 90% and specificity of 97% for the FemExam card test but this publication is only an abstract and in fact these data were not published or peer reviewed [7]. The topic of a card test for BV diagnosis was the subject of two recently presented abstracts [6,9]. One study [8] of 49 women, 26 with BV, concluded that a newer generation of the card test was equivalent to traditional tests, yet another abstract found saline microscopy to be superior to card test [9]. The unique nature of the population in the current study, which includes antibiotic use reported by 18% of the women, clinical findings of 12% of women with genital ulcers, 9% with buboes, and 28% with appreciable cervical discharge, and laboratory findings of 11% diagnosed with T. vaginalis, 6% with N. gonorrhea, and 5% with C. trachomatis, may make comparison with other studies of the FemExam card problematic.

The authors are to be commended for studying the cost of diagnosis and treatment. They find that, in low resource settings with high prevalence populations, empiric treatment as recommended by the WHO is more cost-effective than any other currently available diagnostic method.

References:

1. Schwebke JR.  Diagnostic methods for bacterial vaginosis.  Inter J Gynecol Obstet 1999;67:S21-23.

2. Klebanoff MA, Schwebke JR, Zhang J, Nansel TR, Yu KF, Andrews WW. Vulvovaginal symptoms in women with bacterial vaginosis. Obstet Gynecol 2004;104:267-72. 

3. Amsel R, Totten PA, Spiegel CA, Chen KCS, Eschenbach DA, Holmes KK.  Non specific vaginitis. Diagnostic and microbial and epidemiological associations.  Am J Med 1983;74:14-22. 

4. Spiegel CA, Amsel R, Holmes KK.  Diagnosis of bacterial vaginosis by direct Gram stain of vaginal fluid.  J Clin Microbiology 1983;18:170-7.

5. Nugent RP, Krohn MJ, Hillier SL.  Reliability of diagnosing bacterial vaginosis is improved by a standardized method of Gram stain interpretation.  J Clin Microbiol 1991;29:297-301.

6. Chaudhuri A, Lawrence PJ, Tamerius JD, Soper DE, Schwebke JR. A secondgeneration pH and amines test for bacterial vaginosis. (abstract) Obstet Gynecol 2004;103:24S.

7. Hillier SL, Schwebke J, Sobel J, McGregor J, Sweet RL. Improved reliability of diagnosis of bacterial vaginosis using an objective device for detection of elevated vaginal pH and trimethylamine. Infectious Diseases in Obstetrics and Gynecology 1996;4:348-64 for the entire meeting (this abstract is on page 60).

8. Schwebke JR, Richey CM, Weiss HL. Correlation of behaviors with microbiological changes in vaginal flora. JID 1999;180:1632-6.

9. Joshi R, Whyte P,Ortiz M, Karcz LS. A cost benefit analysis, diagnosing bacterial vaginosis in pregnancy, wet mount versus FemExam card. (abstract) Obstet Gynecol 2004;103:42S

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