Nugent's method in diagnosis of bacterial vaginosis

Nugent et al. suggested a modification of Spiegel's method of scoring Gram-stained vaginal smears for the diagnosis of bacterial vaginosis

• the score, calculated by assessing the presence of large Gram-positive rods (Lactobacillus morphotypes), small Gram-negative/Gram-variable rods (G. vaginalis morphotypes), and curved Gram-variable rods (Mobiluncus spp. morphotypes) can range from 0 to 10 with a score of 7 to 10 being consistent with bacterial vaginosis
• compared to the Amsel criteria, the Nugent's score allows for assessment of alteration in vaginal flora as a continuum rather than a dichotomy

Amsel criteria, despite being less sensitive compared to the Nugent's set of criteria, had a high specificity (94.7%) which is in accordance with the report by Sha et al (1)

The chief drawback of Nugent's method seems to be that it turns out a higher number of false positive cases compared to the Amsel criteria method (2)

Reference:

• 1) Sha BE, Zariffard MR, Wang QJ, Chen HY, Bremer J, Cohen MH, Spear GT Female genital-tract HIV load correlates inversely with Lactobacillus species but positively with bacterial vaginosis and Mycoplasma hominis. J Infect Dis 2005; 191: 25-32.
• 2) Modak T et al. Diagnosis of bacterial vaginosis in cases of abnormal vaginal discharge: comparison of clinical and microbiological criteria. J Infect Dev Ctries. 2011 May 28;5(5):353-60.