Rapid test, throat culture and clinical assessment in the diagnosis of tonsillitis.

Objectives: Our aim was to identify a group of patients with clinical signs of tonsillitis to whom antibiotics could be prescribed without further diagnostic actions, and to compare the outcome of clinical assessment with the result of an antigen detection test using culture as the gold standard.

Methods: During two winter months, patients aged > or =4 years attending for sore throat at three primary health care centres in Malmö, Sweden, were examined. Odds ratios, sensitivities, specificities and predictive values were calculated for clinical assessment and for an antigen detection test.

Results: Among the 169 participating patients, growth of group A beta-haemolytic streptococci (GAS) was found in 53 cultures, and 23 patients (14%) were clinically assessed as 'absolutely positive', representing positive clinical assessment. Nineteen had positive cultures for GAS. The sensitivity, specificity and predictive positive and negative value for the antigen detection test were 82, 96, 90 and 93%, respectively, and for positive clinical assessment 36, 97, 83 and 77%.

Conclusion: It is possible to identify a small group of patients with convincing signs of tonsillitis in which the specificity as well as the predictive positive value of the rapid test and the clinical assessment are close to equal. Antibiotics may be prescribed to these patients without further diagnostic actions.