Evaluation of a Rapid Gram Stain Interpretation Method for Diagnosis of Bacterial Vaginosis

Abstract

A simple Gram stain evaluation for the diagnosis of bacterial vaginosis was assessed in comparison toNugent's method. The sensitivity (90%), specificity (94%), positive and negative predictive values (90% and 94%), and good interobserver agreement obtained indicate that the test method can be performed reliably in the routine clinical microbiology laboratory.Bacterial vaginosis is the most frequent cause of vaginitis (11) and has been associated with severe sequelae (8,12). Symptoms of bacterial vaginosis are nonspecific, and diagnosis should rely on confirmatory tests (3, 6, 10). The two most widely accepted methods for the diagnosis of bacterial vaginosis, Amsel's composite criteria (ACC) (2) and Nugent's Gram stain evaluation of bacterial morphotypes (NBM) (9), are used insufficiently in routine practice (7,14). The former is cumbersome and not easily subjected to quality control, and the apparent complexity of the latter may have limited its adoption by clinical laboratories. The aim of this study was to evaluate a simple interpretation of Gram-stained smears, described by Patients and samples. Women who had a gynecological examination at the Department of Sexually Transmitted Infections at Landspítali University Hospital were recruited after written informed consent was obtained. A dry speculum was inserted into the vagina, and drops of fluid from the fornix were placed in 10% KOH for the amine odor test and on a pH indicator strip (Merck; pH range, 3.8 to 5.4). The presence of a white or gray homogenous discharge was recorded. Vaginal fluid was also sampled on a rayon swab with Amies agar gel (Copan Innovation), stored at 4 to 8°C, and processed within 24 h by rolling on glass slides for a wet mount and Gram staining. At least 20 fields of the wet mount were examined by one observer at ϫ400 magnification in a phase-contrast microscope (Leica DM LB) and the presence or absence of clue cells was recorded to complete the ACC method. The Gram-stained slide was evaluated by three observers according to the TCC method, with three modifications: (i) the slides were read at ϫ500 magnification with oil immersion, (ii) a microscopic field had to contain at least five epithelial cells to be considered valid, and (iii) lactobacilli were defined as any gram-positive, straight, or curved rods that had parallel sides and square ends and measured at least 2 m in length (5). At least 20 fields were examined. Bacterial vaginosis was considered present if non-Lactobacillus morphotypes outnumbered Lactobacillus morphotypes and Ն2 clue cells were seen per 20 fields. The smears were also examined at ϫ1,000 magnification and scored according to the NBM method; intermediate status was classified as being negative for performance evaluation. Leica DM LB and Leitz Diaplan microscopes were used for regular microscopy. Results from each method and observer were blinded from other methods and observers. The study was approved by the institution's Ethical Committee.Analysis. The NBM method was used as the reference method for true-posi...

Screening for Bacterial Vaginosis in Pregnant Adolescents and Women to Prevent Preterm Delivery

“…Forty-four studies from 48 publications were included (Figure 2). Twenty-five studies of test accuracy (KQ2), 13 RCTs evaluating the benefits of treatment with respect to preterm delivery and related pregnancy outcomes (KQ4), and 14 studies evaluating the harms of treatment (KQ5) were identified.…”