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Bacterial Vaginosis: Why is diagnosis important? What are the most sensitive diagnostic methods?
| Author: R. MIMI CLARKE SECOR, MS, M.ED, APPRN, BC, FNP (and) JEANNE M. MARRAZZO, MD, MPH |
| Article Date: 11/1/2007 |
BV occurs when the normal hydrogen peroxide (H2O2)Ðproducing Lactobacillus species in the vagina are replaced by high concentrations of anaerobic bacteria (e.g., G. vaginalis, Prevotella sp. Mobiluncus sp. and Mycoplasma hominis). It is the most common vaginal infection in women of childbearing age. In the U.S., up to 16% of pregnant women have BV. If left untreated during pregnancy it can result in premature rupture of membranes, preterm labor, preterm birth, intra-amniotic infection and postpartum endometritis.1 Several studies have found that treatment of pregnant women with BV (who have a history of preterm delivery) helps to reduce the risk of premature delivery.2 Hence, it is important to diagnose, treat and monitor women throughout their pregnancy if they have had preterm delivery in the past.
Not only is BV a risk in pregnancy, it can also increase the chances of pelvic inflammatory disease, potentially leading to infertility or ectopic pregnancy. Although not definitively proven to be a sexually transmitted disease, BV has been shown to increase the risks of acquiring HIV and other STDs including genital herpes, HPV, gonorrhea and chlamydia.1 Screening for and treating BV during routine exams for women at risk for these infections might contribute to helping women reduce their risk.
Up to fifty percent of women with BV have no symptoms.3 Those who do may complain of increased discharge and/or a fishy odor. Itching may occur as a result of the increased discharge. Many women will attempt to treat this discharge with over the counter anti-fungal medications or various douching products before deciding to visit their health care professional.4 Douching, however, actually promotes the loss of H2O2-producing vaginal lactobacilli. Risk factors for BV include2:
¥ A new sex partner or multiple sex partners (male or female)
¥ Douching
¥ Having an IUD
¥ Hormonal changes due to menopause
¥ Stress5
¥ African American Race
¥ Sex with another woman
Although Gram stain is the gold standard for diagnosis of BV, the most commonly used method is AmselÕs criteria. Research by R. Amsel in 1983 showed a correlation between BV and the presence of at least three of the following four signs:
¥ pH of vaginal fluid > 4.5
¥ Whiff test (a fishy odor of vaginal discharge before or after addition of 10% KOH)
¥ Homogeneous, thin, white discharge that smoothly coats the vulva and vaginal walls
¥ Presence of clue cells upon examination under a microscope
Gram stain uses a scale called the Nugent criteria to determine the relative concentration of lactobacilli (long Gram-positive rods), Gram-negative and Gram-variable rods and cocci (i.e., G. vaginalis, Prevotella, Porphyromonas, and peptostreptococci), and curved Gram-negative rods (Mobiluncus) which are characteristic of BV. Gram stain is typically reserved for research purposes. Both the CDC and ACOG Guidelines recognize the clinical utility of Amsel criteria for the diagnosis of BV.
Other non-waived diagnostic methods include BD Affirm, a DNA probe test with 95% sensitivity versus Gram stain, cervical Pap smear and culture. Culture of vaginal fluid (for example, to detect Gardnerella vaginalis) and cervical Pap smear are not recommended because of poor predictive performance. A new CLIA-waived rapid test, OSOM BVBLUE, is highly sensitive (92.8%) and detects the presence of sialidase, an enzyme produced by the four most common pathogens which cause BV.
Once diagnosed, treatment choices include oral or intravaginal Metronidazole or clindamycin. Intravaginal treatment with Clindamycin is now recommended but only during the first half of pregnancy. For the second half, oral medication should be prescribed, either Metronidazole 500 MG orally twice a day for 7 days, or Clindamycin 300 MG orally twice a day for 7 days. As BV can frequently recur, women should be advised to return for additional therapy if symptoms recur. Because of high recurrence rates of up to 30% at 3 months6, some experts recommend a followup visit after treatment. This should be scheduled approximately one month after therapy is completed to objectively evaluate response to therapy. AmselÕs Criteria should again be assessed.
Single-dose oral metronidazole (2 grams) is no longer recommended due to unacceptably low cure rates.2 Single dose vaginal clindamycin is recommended and is associated with cure rates similar to other regimens.
Schwebke, JR, Desmond R. Risk factors for bacterial vaginosis in women at high risk for sexually transmitted diseases, Sex Transm Dis. 2005;32(11):654-658.
Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines-2006.MMWR. August 4, 2006;55(RR-11):49-52.
Amsel R, Totten PA, Speigal CA, et al. Non-specific vaginitis: diagnostic and microbial and epidemiological associations. Am J Med. 1983;74:14-22.
Ferris, DG, Dekle C, Litaker MS. WomenÕs use of over-the-counter anti-fungal medications for gynecologic symptoms. J Fam. Pract. 1996;42:595-600.
Nansel TR, Riggs MA, Yu K-F, et al. The association of psychosocial stress and bacterial vaginosis in a longitudinal cohort. Am J Obstet Gynecol. 2006;194:381-386.
Sobel JD. Bacterial vaginosis. Ann Rev Med. 2000;51:349-356.
Not only is BV a risk in pregnancy, it can also increase the chances of pelvic inflammatory disease, potentially leading to infertility or ectopic pregnancy. Although not definitively proven to be a sexually transmitted disease, BV has been shown to increase the risks of acquiring HIV and other STDs including genital herpes, HPV, gonorrhea and chlamydia.1 Screening for and treating BV during routine exams for women at risk for these infections might contribute to helping women reduce their risk.
Up to fifty percent of women with BV have no symptoms.3 Those who do may complain of increased discharge and/or a fishy odor. Itching may occur as a result of the increased discharge. Many women will attempt to treat this discharge with over the counter anti-fungal medications or various douching products before deciding to visit their health care professional.4 Douching, however, actually promotes the loss of H2O2-producing vaginal lactobacilli. Risk factors for BV include2:
¥ A new sex partner or multiple sex partners (male or female)
¥ Douching
¥ Having an IUD
¥ Hormonal changes due to menopause
¥ Stress5
¥ African American Race
¥ Sex with another woman
Although Gram stain is the gold standard for diagnosis of BV, the most commonly used method is AmselÕs criteria. Research by R. Amsel in 1983 showed a correlation between BV and the presence of at least three of the following four signs:
¥ pH of vaginal fluid > 4.5
¥ Whiff test (a fishy odor of vaginal discharge before or after addition of 10% KOH)
¥ Homogeneous, thin, white discharge that smoothly coats the vulva and vaginal walls
¥ Presence of clue cells upon examination under a microscope
Gram stain uses a scale called the Nugent criteria to determine the relative concentration of lactobacilli (long Gram-positive rods), Gram-negative and Gram-variable rods and cocci (i.e., G. vaginalis, Prevotella, Porphyromonas, and peptostreptococci), and curved Gram-negative rods (Mobiluncus) which are characteristic of BV. Gram stain is typically reserved for research purposes. Both the CDC and ACOG Guidelines recognize the clinical utility of Amsel criteria for the diagnosis of BV.
Other non-waived diagnostic methods include BD Affirm, a DNA probe test with 95% sensitivity versus Gram stain, cervical Pap smear and culture. Culture of vaginal fluid (for example, to detect Gardnerella vaginalis) and cervical Pap smear are not recommended because of poor predictive performance. A new CLIA-waived rapid test, OSOM BVBLUE, is highly sensitive (92.8%) and detects the presence of sialidase, an enzyme produced by the four most common pathogens which cause BV.
Once diagnosed, treatment choices include oral or intravaginal Metronidazole or clindamycin. Intravaginal treatment with Clindamycin is now recommended but only during the first half of pregnancy. For the second half, oral medication should be prescribed, either Metronidazole 500 MG orally twice a day for 7 days, or Clindamycin 300 MG orally twice a day for 7 days. As BV can frequently recur, women should be advised to return for additional therapy if symptoms recur. Because of high recurrence rates of up to 30% at 3 months6, some experts recommend a followup visit after treatment. This should be scheduled approximately one month after therapy is completed to objectively evaluate response to therapy. AmselÕs Criteria should again be assessed.
Single-dose oral metronidazole (2 grams) is no longer recommended due to unacceptably low cure rates.2 Single dose vaginal clindamycin is recommended and is associated with cure rates similar to other regimens.
Schwebke, JR, Desmond R. Risk factors for bacterial vaginosis in women at high risk for sexually transmitted diseases, Sex Transm Dis. 2005;32(11):654-658.
Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines-2006.MMWR. August 4, 2006;55(RR-11):49-52.
Amsel R, Totten PA, Speigal CA, et al. Non-specific vaginitis: diagnostic and microbial and epidemiological associations. Am J Med. 1983;74:14-22.
Ferris, DG, Dekle C, Litaker MS. WomenÕs use of over-the-counter anti-fungal medications for gynecologic symptoms. J Fam. Pract. 1996;42:595-600.
Nansel TR, Riggs MA, Yu K-F, et al. The association of psychosocial stress and bacterial vaginosis in a longitudinal cohort. Am J Obstet Gynecol. 2006;194:381-386.
Sobel JD. Bacterial vaginosis. Ann Rev Med. 2000;51:349-356.