Validation and inter-examiner agreement of mutans streptococci levels in plaque and saliva of 10-year-old children using simple chair-side tests

Since there are few validation studies of chair-side tests of oral mutans streptococci, we compared a commercially available strip test with the conventional laboratory assay. Two plaque samples obtained from the mesial surfaces of the upper right and lower left permanent molars of sixty-five 10-year-old children (boys = 38, girls = 27) were cultured and incubated using chair-side site strip tests (Dentocult SM, Orion Diagnostica). Two plaque sampling tools, namely dental floss and micro-brush, were compared, and inter-examiner agreement between recordings of three examiners was assessed. Paraffin-stimulated saliva was then collected for laboratory and chair-side assays. The plaque and saliva chair-side tests correlated well with each other (Spearman rho, r = 0.72) and with the laboratory method, showing coefficients of 0.76 and 0.80 for saliva and plaque, respectively. Compared to the laboratory method, the sensitivity (Sn), specificity (Sp), accuracy (A), and kappa (K) values of the salivary and plaque chair-side tests were 0.63, 0.75 (Sn), 0.93, 0.90 (Sp), 0.82, 0.85 (A), and 0.58, 0.66 (K), respectively. Agreement between the two plaque sampling techniques was good (0.91). Inter-examiner agreement of plaque scores ranged between 0.65 and 0.86 when all density categories were analysed separately; when dichotomized into low and high categories, complete agreement was found. Agreement between the plaque and saliva chair-side tests and the laboratory salivary assay was good, and in terms of sensitivity, accuracy, and kappa values, the site strip plaque test surpassed the salivary chair-side test.