Bacterial vaginosis is one of the most common occurring vaginal conditions among women of reproductive age. A rapid and reliable laboratory test for diagnosis of
bacterial vaginosis would be helpful in the clinical detection of this disease. Elevated
proline aminopeptidase activity has been identified as a reliable marker
enzyme for
bacterial vaginosis. A
proline aminopeptidase assay has been shown to predict accurately women with a clinical diagnosis of
bacterial vaginosis. However, this assay has significant practical disadvantages, the most notable of which is the production of a carcinogenic end product,
alpha-naphthylamine. We have developed a modified assay for this
bacterial vaginosis marker
enzyme with
L-proline p-nitroanilide, a substrate that does not yield a carcinogenic end-product. The new
proline aminopeptidase assay is a one-step test that is analyzed colorimetrically with microsomal
leucine aminopeptidase used as a standard
enzyme (linear from 3 to 125 mU per well). We have determined the activity of
proline aminopeptidase in vaginal wet preparations from 57 patients with both assay methods. In addition, vaginal smears were examined with
Gram's stain and analyzed for
bacterial vaginosis with the Spiegel method. When compared with the Spiegel method, the two
proline aminopeptidase assay methods were similar with respect to assay sensitivity (93%), specificity (91% to 93%), and the predictive value of a positive result (78% to 82%) or a negative result (97% to 98%). Vaginal wash samples also were assessed for
proline aminopeptidase activity. Values for samples identified as
bacterial vaginosis positive were significantly different (p less than 0.0001) from those that were negative according to the Spiegel analysis of
Gram's stain: negative results, 66 +/- 41 mU/ml; positive results, 704 +/- 145 mU/ml. These findings indicate that this improved
proline aminopeptidase assay will offer a rapid, sensitive, and objective laboratory method for the diagnosis of
bacterial vaginosis.