LabMed

Vaginitis

At a Glance

Trichomoniasis, vulvovaginal candidiasis, and bacterial vaginosis comprise 90% of cases of infectious vaginitis or vulvovaginitis. A history of symptoms should include vaginal discharge and odor, mode of onset (abrupt or insidious), vaginal irritation, and abdominal pain.

Trichomoniasis is notable for vulvar and vaginal erythema with a purulent, rarely frothy, vaginal discharge. Candida vulvovaginitis often presents with little to no discharge; the primary symptoms are vulvovaginal pruritis, edema, irritation, and occasional dysuria. Up to 75% of adult women will report at least one episode of vaginitis due to Candida during their lifetimes. However, vaginal candidiasis is rare in prepubescent girls. Other risk factors for candidiasis include prior antibiotic use, oral contraceptive use, poorly controlled diabetes mellitus, and impairment of cellular immunity. Bacterial vaginosis, a disorder of microbial imbalance of which Gardnerella vaginalis is but one component, often presents with an odorous, thin, gray discharge.

Abrupt onset of vaginal symptoms suggests an infection. Abdominal pain is suggestive of pelvic inflammatory disease or cystitis, rather than vaginitis.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Vaginitis can be assessed by a series of office-based tests. However, atypical or recurrent cases or those cases that occur in immunocompromised individuals may warrant laboratory-based testing.

In the office, the vaginal secretions should be sampled and examined for pH and odor. A wet preparation and potassium hydroxide (KOH) preparation should be performed.

A vaginal pH should be obtained by a pH test strip. The normal vaginal pH ranges from 3.8 to 4.6. In Trichomonas infection and bacterial vaginosis, the vaginal pH is greater than 4.5. A vaginal pH greater than 5 is strongly suggestive of bacterial vaginosis.

A whiff test is performed by placing a small drop of vaginal secretion onto a slide, adding 10% KOH, and assessing for odor. A fishy odor is indicative of bacterial vaginosis.

The wet mount should be examined within 10-20 minutes for the presence of motile trichomonads, which have a twitching or jerky motion. However, in 30% of patients with culture-proven trichomoniasis, the wet mount is negative. The presence of polymorphonuclear neutrophils (PMNs) and epithelial cells should also be assessed. A finding of many more PMNs than epithelial cells raises the suspicion of cervical or vaginal inflammation. A paucity of PMNs does not rule out vaginitis, however. In fact, the relative absence of PMNs is suspicious for bacterial vaginosis and possibly also candidiasis. Clue cells are epithelial cells covered with small coccobacillary forms. Clue cells are indicative of bacterial vaginosis.

Finally, a KOH preparation can be examined after combining a drop of 10% KOH to help detect the presence of fungal elements. The table summarizes the diagnostic criteria of vaginal infections using office-based testing.

In the laboratory, a Gram stain of the vaginal material can be performed and the specimen “graded” for bacterial vaginosis by the Nugent criteria. The Nugent criteria correlate closely with the Amsel criteria. Commonly used in clinical practice, the Amsel criteria include homogenous discharge, positive whiff test, pH greater than 4.6, and clue cells. At least 3 of the 4 criteria are needed for diagnosis of bacterial vaginosis.

The technologist performing the vaginal Gram stain assesses for the presence of gram-variable G. vaginalis, as well as for Mobiluncus, a curved gram-negative rod associated with most cases of bacterial vaginosis. Normal vaginal flora consist primarily of gram-positive bacilli, which are primarily lactobacilli. Although fungi stain gram-positive, the Gram stain is typically negative in women with positive Candida cultures. In addition, Trichomonas is distorted when stained by the Gram stain, rendering diagnosis difficult. For these reasons, as well as for the laboratory expertise needed in interpretation, the Gram stain is typically performed in the laboratory setting, rather than in the office setting.

Occasionally, trichomonads are reported from Papanicolaou smears, but the sensitivity of this technique is only 50-60% and many false-positive results have been reported.

Cultures for Trichomonas and Candida may also be performed in the laboratory. Culture for trichomoniasis improves the diagnostic yield over wet mount, particularly in asymptomatic patients. In a symptomatic patient with a diagnostic wet preparation and physical examination, it is not necessary to submit a sample to the laboratory for Trichomonas or Candida culture. Culture for Trichomonas may be performed using the InPouch TV Trichomonas vaginalis system (BioMed Diagnostics, Inc., WhiteCity, Oregon, U.S.) or Diamond’s medium. Cultures for Candida may be helpful in the symptomatic patient with a negative microscopic examination and in recurrent cases of vulvovaginal candidiasis.

Although culture for Gardnerella vaginalis is available on a variety of media, it is not useful, as the organism is demonstrated on culture in at least 50% of asymptomatic women. It is now known that Gardnerella vaginalis is only one type of bacteria associated with bacterial vaginosis, a multi-organism disease resulting from synergistic infection with many types of bacteria. Molecular analyses of vaginal secretions of women with bacterial vaginosis have shown novel species of bacteria, some of which are highly specific for bacterial vaginosis.

Office-based rapid diagnostic point-of-care tests, such as rapid antigen and molecular probe testing, are widely available. Card tests that assess for elevated vaginal pH and increased amines can be used to confirm bacterial vaginosis, especially if microscopy is not available.

The point-of-care Affirm VP III Microbial Identification System (Becton, Dickinson and Company, Franklin Lakes, NJ, U.S.) employs nucleic acid probe technology. This test detects the presence of C. albicans, T. vaginalis, and abnormally high concentrations of G. vaginalis in patient vaginal secretions. Sensitivity and specificity of this test exceed 95%, and the run-time of the assay is 45 minutes. The OSOM® Trichomonas Rapid Test (Sekisui Diagnostics) is another rapid 10-minute immunochromatographic test that detects the Trichomonas antigen with a sensitivity and specificity of 88% and 99%, respectively.

Laboratory-based molecular testing for G. vaginalis is not useful because of the high prevalence of G. vaginalis in the asymptomatic patient population.

Clinical diagnosis is generally based on a combination of symptoms and office-based testing. However, when treatment is failing or if the patient is suffering from recurrences, culture or other specific laboratory-based testing should be performed. If vulvovaginal candidiasis is diagnosed, susceptibility testing may be performed if the patient has failed treatment.

Follow-up testing for test-of-cure is not necessary for these disorders once treatment has begun and the patient’s symptoms have resolved. (Table 1)

Table 1.

Diagnostic Criteria for Vaginal Infections
Diagnostic Criteria Normal Bacterial Vaginosis Candida Vulvovaginitis Trichomonas Vaginitis
Vaginal pH 3.8-4.5 >4.5 <4.5 (usually) >4.5
Vaginal Discharge Clear or white, flocculent Thin homogeneous, milky white or gray, adherent, often increased in volume White, curdy like “cottage cheese,” sometimes increased in volume Yellow, green, frothy, adherent, increased in volume
Amine odor (KOH “whiff” test) Absent Present (fishy) Absent Often present (fishy)
Common Patient Complaints None Discharge, fishy odor-possibly worse after intercourse, itching may be present Itching/burning, increased discharge Frothy discharge, bad odor, vulvar discomfort, dysuria
Microscopy (Wet prep/KOH prep) Lactobacilli, epithelial cells Clue cells with adherent coccoid bacteria, no white blood cells (WBCs) Budding yeast, hyphae, pseudohyphae (with KOH prep) Trichomonads, WBCs > 10/HPF

Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?

Many substances may raise the vaginal pH, such as blood, semen, douche preparations, cervical secretions, and intravaginal medications. As the pH of normal vaginal secretions increases in premenarchal and postmenopausal women (usual pH 4.7 or more), measurement of pH at these ages is less useful.

Trichomonas only survive short periods of time outside the body. Wet preparations should be examined for motile trophozoites within 10-20 minutes. Fresh urine and vaginal swabs, which are not in appropriate transport media, may be submitted to the Microbiology Laboratory for culture only if the specimens are received within 1 hour. They are then processed immediately on receipt. However, Trichomonas may survive up to 24 hours in the appropriate Trichomonas culture medium, which also serves as the transport media, before being processed for culture in the Microbiology Laboratory.

What Lab Results Are Absolutely Confirmatory?

The motile trophozoite forms of Trichomonas seen on wet preparation are confirmatory for trichomoniasis. Filamentous forms of Candida may be seen on wet mount as hyphae and pseudohyphae. These forms are often associated with active disease, as they are more adherent to the vaginal epithelium than the budding yeast or conidial forms. Many of the laboratory tests mentioned, such as culture, molecular, and card-based assays, have high specificities.

What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?

Candida albicans is present in 80-90% of patients with vulvovaginal candidiasis on culture. However, the relative incidence of candidiasis due to Candida species other than C.albicans, such as Candida glabrata and Candida tropicalis, is increasing. This rise in non-C.albicans is important, as these species may not respond as well to triazole treatment.

You must be a registered member of Renal and Urology News to post a comment.

Sign Up for Free e-newsletters