Diagnosis of Bacterial Vaginosis Pelvic examination Vaginal pH and microscopy If microscopy is unavailable, sometimes nucleic acid amplification tests (NAATs) For bacterial vaginosis to be diagnosed, 3 of 4 criteria (Amsel criteria) must be present: Yellow-green or gray discharge Vaginal secretion pH > 4.5 Fishy odor on the whiff test (application of potassium hydroxide) Clue cells on saline (0.9%) wet mount Clue cells (bacteria adhering to epithelial cells and sometimes obscuring their cell margins) are identified by microscopic examination of a saline wet mount.