The validity of the McIsaac clinical decision rule in the detection of group A beta hemolytic streptococcus pharyngitis using throat culture as the reference standard

ABSTRACT

BACKGROUND: During a monthly morbidity and mortality report in family medicine it was noted that one of the most frequent illness encountered was sore throat or acute pharyngitis. It accounted among the top five most common comorbidities in out-patient consults and emergency room admissions in 2015-2016.OBJECTIVE: This study was conducted in Chong Hua Hospital to evaluate if a sore throat scoring system such as the McIsaac Decision Rule was valid in detecting group A beta hemolytic streptococcus pharyngitis and was reliable as a clinical approach in managing sore throat.DESIGN: A prospective, descriptive survey was done among patients who consulted and eventually admitted at the emergency room and OPD under the family medicine department at Chong Hua Hospital Cebu City.METHODS: A total of 23 patients; children and adults who presented with sore throat were assessed. A data extraction form utilizing criteria from the McIsaac clinical rule known as "Sore Throat Encounter Form" was used for each patient encounter. The following criteria were accounted; fever >38°C, swollen, tender anterior cervical lymph nodes, tonsillar exudate and absence of cough. A corresponding point was assigned based on the patient's age. Points are summed up and used as basis of management; patients presenting with a score of -1 and 0 could be managed without antibiotic treatment and no throat culture is required. For scores of 1-3 throat culture is indicated and positive results should be treated. For 4-5 scores on an empiric antibiotic treatment should be initiated without the need of throat culture. A throat swab for culture was obtained as a reference standard. In addition, physicians' prescribing practices and their recommendations for obtaining throat swabs were compared with score-based recommendations.RESULTS: Categorical data were expressed in frequency and percentages. McIsaac clinical decision rule assessment results and findings of gold standards were tested for association using 2x2 Fisher's exact test wherein the p-value lesser than 0.05 alpha was considered significant. Accuracy of McIsaac clinical decision rule assessment was computed using sensitivity, specificity, likelihood ratio positive, negative, and positive predictive values.CONCLUSION: The McIsaac Clinical Decision Rule has demonstrated clinically acceptable diagnostic accuracy in predicting streptococcus pharyngitis. Thus, it can be a reliable and valid risk assessment tool to predict and rule out Group A Beta Hemolytic Streptococcus Pharyngitis.