[Is streptococcal pharyngitis diagnosis possible?]

To determine the validity of the Centor score (cervical adenopathy, tonsillar exudate, fever, and absence of catarrh symptoms) in diagnosing streptococcal pharyngitis (gold standard: throat swab).

Descriptive study.

San Fernando 2 Health Centre, Madrid (outer urban area), Spain.

On hundred forty patients over 14 years old who had a "sore throat" as main symptom and attended clinic between 14 February and 12 May, 2005.

Sensitivity, specificity, positive and negative predictive values, and the probability quotients of the Centor score were determined. Pharyngeal throat culture was used as the reference method.

Thirty four patients had positive throat culture (24.3%; 95% CI, 17.6%-32.4%). Finding the 4 criteria in the Centor score had a positive predictive value (PPV) of 48.1% (95% CI, 30.7%-66.0%) and a negative predictive value (NPV) of 81.4% (95% CI, 73.3%-87.5%); although only fever (OR, 3.64; 95% CI, 1.40-9.49) and tonsillar exudate (OR, 6.18; 95% CI, 2.08-18.35) were linked to streptococcal aetiology.

The high NPV and specificity of the clinical score makes the diagnosis of non-streptococcal pharyngitis very accurate. However, the PPV is low: a high Centor score (3 or 4 criteria) does not mean streptococcal pharyngitis with certainty. What approach to take with patients suspected of streptococcal pharyngitis is not yet resolved (microbiological test, early antibiotic, or postponed antibiotic).