Evaluating Bacterial Vaginosis Using The Nugent Scoring System

Project and Seminar Material for Science Laboratory Technology SLT

Evaluating Bacterial Vaginosis Using The Nugent Scoring System


Background And Objective:

Bacterial vaginosis is the most common form of vaginal infection in women of reproductive age. It is a condition with diverse etiology and an important cause of morbidity in women of reproductive age. This study was carried out to determine the accuracy of using the Nugent scoring system as a means of diagnosing Bacterial vaginosis.

Materials And Method:

The prospective study was conducted in Benin City, Edo state between July and September 2012 and included 67 women between the ages of 16 and 45 years. Specimens collected from the lateral wall of the vagina were subjected to Gram staining and the microscopic slides examined and the different morphotypes of bacteria quantified using the Nugent scoring system.


The age range was 16-45 years with a mean of 24.9 years. BV was diagnosed by the Nugent method in 13.4% of women with the highest prevalence found in the age group of 16-20 years. The relationship of a positive whiff test, presence of clue cells and a pH>4.5 with bacterial vaginosis was shown to be highly significant (p=0.0051, P=0.001, P=0.0077).


Nugent scoring system appears to be a reliable and convenient method for laboratory evaluation of cases of bacterial vaginosis.

Keywords: Bacterial Vaginosis, Nugent’s score, Gram staining.

Chapter One


Vaginal bacteria communities are composed of mixtures of diverse species and the relative abundance of these species in part determine urogenital health and disease in women. It is generally acknowledged that vaginal bacterial communities predominated by Lactobacillus species are normal and healthy while communities predominated by other genera such as Gardnerella vaginalis are abnormal and unhealthy. This latter condition essentially describes a poorly understood syndrome known as Bacterial Vaginosis (BV).

The composition of vaginal flora is the focus of interest of recent investigation because of its importance to women’s reproductive organ and general health (Patta et al, 2008). The condition is although common but under diagnosed. This may be due to confusion over its microbial origin (O’Dowd et al., 1996). The vagina is a dynamic ecosystem that is balanced due to the interaction of factors of the native bacterial biota. In healthy adult women, the normal vaginal pH is < 4.5. The predominant species of lactobacilli maintain a low pH through their fermenting activity which protects the area against the invasion of undesirable microorganisms (Pascual et al., 2006). The acidic medium produced by Lactobacilli suppresses the growth of other microorganisms (Klebanoff et al., 1991). Clinically, malodorous vaginal discharge, especially a fishy odour is the most common symptom (Fluery, 1981). Various studies have found the prevalence of BV to range from 15 to 30 per cent in non pregnant women and up to 50 per cent in pregnant women (Nelson and Macones, 2002).

Clinical studies have demonstrated an association of BV with adverse pregnancy outcomes, upper genital tract infections such as pelvic inflammatory disease, endometritis, post-gynaecologic surgery infections, cervicitis, urinary tract infections, cervical intraepithelial neoplasia, and increased risk of sexual acquisition of human immunodeficiency virus infection (Lanzafame, 2002). Given its high prevalence and association with obstetrical and gynaecological complications, detection of this entity in women is of paramount importance. Studies using cultivation methods have shown that women with bacterial vaginosis have loss of vaginal lactobacilli and concomitant overgrowth of anaerobic and facultative bacteria.

Several bacteria have been implicated in bacterial vaginosis, such as Gardnerella vaginalis (Gardner and Duke, 1955) and Mobiluncus curtisii (Spiegel et al., 1983) but these species are also found in subjects who do not have bacterial vaginosis and thus are not specific markers for the disease (Spiegel, 1991). For this reason, bacterial cultivation of vaginal fluid has not proved useful for the diagnosis of bacterial vaginosis. Rather, clinical criteria or Gram’s staining of vaginal fluid is used for diagnosis. The clinical criteria of diagnosing BV is confirmed using the composite criteria described by Amsel et al in 2002 in which 3 or 4 of the following have to be present for diagnosis;

  1. A thin homogenous discharge.
  2. Elevated vaginal pH above 4.5
  3. Release of amines on addition of 10 percent potassium hydroxide solution to vaginal fluid.
  4. The presence of clue cells on wet mount.

However, Amsel criteria may not be adequate to diagnose patients, as approximately 50 percent of BV patients may be asymptomatic (Gregor et al., 2002). Further, there exists a continuum from normal lactobacillus dominated flora through “to severe BV” with an intermediate category which the Amsel criteria fail to recognize. Thus, grading the microbial flora seen in Gram-stained vaginal smears, especially the scoring criteria proposed by Nugent et al in 1991, as an alternative method has become useful as a diagnostic tool.

In this system, large Gram-positive rods (Lactobacillus morphotypes), small Gram-negative to Gram-variable rods (Gardneralla vaginalis and Bacteroides morphotypes) and curved Gram negative rods (Mobiluncus species) are quantitated and a summation score is obtained. BV is not a new clinical condition rather it is an infection that is under recognized and misdiagnosed in developing countries including Nigeria. Due to this under recognition, most clinicians do not even recognize BV diagnosis as a routine laboratory investigation for females of child bearing age. This study was carried out to determine the accuracy of using the Nugent scoring system as a means of diagnosing BV.

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