DIAGNOSIS
The diagnosis of BV can be made based on the history, physical examination, and microscopic examination of the vaginal discharge. Unlike with many other bacterial diseases, culture is not recommended for diagnosis of BV because many of the implicated organisms cannot be easily isolated in the laboratory, and because asymptomatic women also have small numbers of these flora in the vagina.
In 1991, Nugent et al11 described a Gram stain scoring system of vaginal smears to diagnose BV, which has a sensitivity and specificity of 96% and 96%, respectively; it remains the gold standard for diagnosis.7 However, because this method requires considerable time and skill, it is not routinely used in most clinic settings.
A widely used method of diagnosing BV is the Amsel criteria (see Table 1). The Amsel method has a sensitivity and specificity of 81% and 94%, respectively.1,12 The presence of clue cells is the most reliable indicator of BV (see figure). The positive predictive value of this test for the presence of BV is 95%.14 The Amsel method requires microscopy,4,12 which is not always available in clinics.
There are several commercially available point-of-care tests for BV that do not require microscopy. These include rapid antigen and nucleic acid amplification tests to detect elevated levels of G vaginalis, as well as tests that detect the presence of bacterial amines, elevated vaginal pH, and bacterial sialidase.4,7,15 Compared with the Nugent and Amsel methods, one test that detects elevated vaginal fluid sialidase activity was shown to have a sensitivity of 88% and specificity of 91% to 95%.4,7,15 These point-of-care tests are most effective for diagnosing BV when the vaginal pH exceeds 4.5 and when they are used in conjunction with other clinical criteria.
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