A new study indicates that current clinical prediction rules used by physicians to determine whether children have "strep throat" caused by group A streptococcal infection may not be accurate. The study is published in CMAJ (Canadian Medical Association Journal).

Group A streptococcus bacteria cause about 30%-40% of sore throats (pharyngitis) in children; the remaining cases are usually viral. Antibiotics are used to treat bacterial infections, but because there is overlap between symptoms of bacterial and viral pharyngitis, most clinical guidelines recommend microbiologic testing with a rapid antigen detection test or a throat culture.

European guidelines recommend that all children undergo a rapid antigen test to determine the presence of group A streptococcal infection, whereas North American guidelines recommend selective testing. Clinical prediction rules combining symptoms and signs have been created to help physicians identify low-risk patients who can be managed without testing or antibiotics and high-risk patients who need antibiotics without testing.

Dr. Jérémie Cohen, from the Obstetrical, Perinatal and Pediatric Epidemiology Research Team, Research Center for Epidemiology and Biostatistics Sorbonne Paris Cité, Paris Descartes University, Paris, France, and coauthors undertook a study to determine the accuracy of clinical prediction rules in children with pharyngitis. As part of the study, 17 pediatricians and 676 children with a mean age of 6 years participated. The French researchers applied 6 clinical prediction rules to each patient, with the most common predictors used for streptococcal infection being lymph node tenderness, fever, age of child, tonsillar swelling and presence of pus. They found that none of the clinical rules had results that met their target for accuracy.

"This study provides evidence that clinicians should not rely on existing clinical prediction rules for diagnosing streptococcal pharyngitis," states Dr. Cohen.

"The clinical relevance of clinical prediction rules for triaging children who should undergo group A streptococcal testing was poor in this study, in which both high sensitivity and specificity were expected," write the authors.