Concordance of clinical findings and clinical judgment in the diagnosis ofstreptococcal pharyngitis

Objective: It is uncertain how reliably clinicians apply clinical predictor s of group A beta hemolytic streptococcal pharyngitis (GABHSP) to form a cl inical impression, and how reliably this impression predicts culture result s. The objective was to study clinician accuracy in diagnosing GABHSP. Meth ods: This was a prospective cohort study, conducted at an urgent care cente r of a major university. A convenience sample of 218 patients, aged 9-83 ye ars, presenting with sore throat, was enrolled. Symptoms and signs of phary ngitis were documented on a standardized form; the likelihood of GABHSP was plotted on a visual analog scale; and throat culture was obtained. A compa rison was then made between the clinical impression on presentation and the throat culture result. Results: Throat cultures were positive for GABHSP i n 41 patients (19%). The probability of GABHSP was related to node size and tenderness, tonsillar exudate and hypertrophy, and pharyngeal erythema (p < 0.05); but not throat soreness, degree of fever, or cough. A strong clini cal impression of GABHSP (>50% on the visual analog scale) was associated w ith tonsillar exudate and hypertrophy, tender nodes, and pharyngeal erythem a. Together, these four predictors had a sensitivity of 71%, a specificity of 77%, and a positive predictive value of 46%. Conclusions: Clinicians in this study based their impression of GABHSP on the most reliable symptoms a nd signs. While a strong clinical suspicion of GABHSP predicted a greater p robability of positive culture, the clinicians consistently overestimated t he probability of GABHSP. Symptoms and signs predict GABHSP unreliably when used alone; they are helpful in modifying estimates of disease probability to facilitate optimal use of laboratory tests and antibiotics.