Multivariate predictive models for group A beta-hemolytic streptococcal pharyngitis in children

Objectives: To create predictive models for the clinical diagnosis of group A beta-hemolytic streptococcal (GABHS) pharyngitis in children. Methods: P atients aged 6 months to 18 years presenting to a pediatric ED with suspect ed GABHS pharyngitis were prospectively enrolled in the study. Clinicians r ecorded pertinent clinical information using a standardized form and obtain ed a throat swab to culture GABHS using a reference standard method. Twelve demographic and clinical features of patients with positive throat culture s were compared with the features of patients with negative throat cultures . Significantly different features were entered in a stepwise logistic regr ession analysis to create predictive models for the diagnosis. Results: Eig hty-five patients (29%) were culture-positive and 212 (71%) were culture-ne gative for GABHS. Respective mean ages were 6.2 years and 6.1 years in the two groups. Univariate chi-square analysis of the 12 features identified si x variables that were significantly associated with GABHS. All significant features were initially included in a stepwise logistic regression analysis . In model I, four independent variables were identified: moderate to sever e presentation of tonsillar swelling, moderate to severe tenderness and enl argement of cervical lymph nodes, the presence of scarlatiniform rash, and the absence of moderate to severe coryza, yielding a 95% probability for GA BHS. Excluding the rare scarlatiniform rash, the remaining variables were u sed in the second regression analysis. In model II, three independent varia bles were identified: moderate to severe tonsillar swelling, moderate to se vere tenderness and enlargement of cervical lymph nodes, and absence of mod erate to severe coryza, yielding a probability of 65% for the diagnosis. A probability of <15% was observed in the absence of scarlatiniform rash, the absence of moderate to severe tenderness and enlargement of cervical lymph nodes, and the presence of moderate to severe coryza. Conclusions: In chil dren with moderate to severe presentation of tonsillar swelling, tenderness and enlargement of cervical lymph nodes, and the absence of coryza, the pr obability of a positive throat culture is >65%. Conversely, in the absence of a moderate to severe presentation of tonsillar swelling, enlargement of cervical nodes, and the presence of coryza, the probability of a positive t hroat culture is <15%. If prospectively validated, these models could be in tegrated into a consistent treat, test, and no treatment/no testing approac h to the clinical management of childhood pharyngitis.