Common clinical features as predictors of bacterial diarrhea in infants.

Identification of infants with bacterial diarrhea during the first year of life is important to limit potentially serious complications, but indications for stool leukocyte examination and culture are not well defined. The ability of three clinical features--temperature, history of blood in the stool, and stool frequency--to predict the presence of bacterial gastroenteritis was analyzed. Over a 1-year period, 108 (10.4%) bacterial pathogens were isolated from 1,035 infants aged less than 1 year with diarrhea. Bacterial culture was positive in 14.9% of cases from May to October, compared with 6.2% of cases from November to April. A history of blood in the stool was the best individual predictor with sensitivity of 39%, specificity of 88%, and a positive predictive value of 30%. Temperature greater than 39 degrees C had sensitivity of 34% and specificity of 85%; greater than or equal to 10 stools in 24 hours had sensitivity of 28% and specificity of 85%. Using combinations of factors, we identified (1) a group of patients at high risk for bacterial diarrhea (infants with two of the three factors studied); (2) a low-risk group (those with temperature less than or equal to 38 degrees C, less than 10 stools in 24 hours, and the absence of blood in the stool); and (3) a group at intermediate risk for bacterial diarrhea (all other patients). We recommend routine stool cultures for infants with a high-risk combination. Additional clinical and laboratory features, such as stool leukocytes, should be studied among patients in the intermediate-risk group.