Bacterial vaginosis has universal acknowledgment as the most prevalent cause of vaginal disorders in women of reproductive age, present in an estimated 10 to 20% of White women and 30 to 50% of Black women. Estimates for the exact percentage of women afflicted at any one time vary from as low as 5% to as high as 70% worldwide. If symptomatic, patients often complain of vaginal discharge having a classic "fishy" odor; however, many women remain asymptomatic until detection during a routine vaginal exam or pap smear. Unfortunately, leaving bacterial vaginosis untreated provides an opportunity for several complications including inflammation of endometrial or cervical tissue, urinary tract infection, chronic pelvic pain, increased risk of HIV and other STDs, and elevated risk of ectopic pregnancy as well as difficult conception. As pertains to pregnancy, consequences may be even more severe and include the potential for prematurity of the newborn, premature rupture of membranes, and low birth weight.
Treatment for this issue generally involves antibiotic therapy via intravaginal gel or oral pill. Metronidazole or clindamycin are the most commonly used antimicrobial agents. Unfortunately, the complete cure rate for bacterial vaginosis is between 65 to 85 percent, and many women experience a relapse in the weeks or months following treatment.
The Nugent scoring system had previously been considered the gold standard for the diagnosis of bacterial vaginosis. This system, discovered by RP Nugent and published in 1991, added more specific qualifications to the previous gold standard, the Spiegel criteria - otherwise known as Gram staining of vaginal smears. Using the Nugent score, vaginal smears are plated on a microscopic slide in oil immersion, and a minimum of 10 high power fields are examined for three bacteria morphotypes: Lactobacillus, Gardnerella, and curved gram rods. Each of these three categories receives a score based on the number of bacteria counted. Subsequently, these three scores are added together for a total score ranging from 0 - 10. The scoring is as follows:
- 0–3: negative for BV
- 4–6: intermediate
- 7+: positive for BV
While accurate, the Nugent scoring system has been disregarded by many physicians as cumbersome due to the skill level required with microscopy as well as the time it takes to physically perform bacteria counts. The Amsel criteria have, by and large, replaced the Nugent system.
The Amsel criteria, originally published in the American Journal of Medicine in 1983, provides a more accessible, clinically defined basis for the diagnosis of bacterial vaginosis using only four criteria. Though older and seemingly simpler, the Amsel criteria have been validated as equivalent to Nugent scoring when diagnosing bacterial vaginosis. It is generally preferred for its ease and ability to be performed using only basic observational microscopic techniques.