Final answer:
To diagnose bacterial vaginosis, three out of four Amsel's criteria must be met: a white to yellow discharge, a fishy odor upon addition of 10% KOH, a vaginal pH above 4.5, and the microscopic identification of clue cells.
Step-by-step explanation:
Three out of four criteria are required to diagnose bacterial vaginosis (BV). These criteria include: 1) a white to yellow discharge; 2) a fishy odor, which is most noticeable when 10% KOH is added to the sample; 3) a vaginal pH greater than 4.5; and 4) the presence of clue cells on microscopic examination. The diagnosis of BV can accurately be made by evaluating these Amsel's diagnostic criteria, which encompass clinical symptoms and evaluation of vaginal fluids.
Additionally, microscopic examination of gram-stained vaginal smears can reveal a morphological shift from gram-positive bacilli to gram-negative coccobacilli and the presence of clue cells. Culturing the causative organisms like G. vaginalis is less indicative as it can be found in healthy individuals as well. Hence, direct examination of vaginal secretions plays a crucial role in diagnosing bacterial vaginosis.