Vaginal swab is obtained, spread on a glass slide, air dried and at a later time gram stained and the bacterial mortphotypes are quantified. Nugent criteria:

each morphotype is quantified separately according to the average number of each per oil immersion field:

0 = no organisms

1+ = <1

2+ = 1-4 organisms

3+ = 5-30

4+ = >30

Total score >=7 consistent with BV, intermediate score 4-6