The value of strep A OIA and CRP in diagnosing strep throat

Objectives: Early identification and treatment of group A betahemolytic streptococcal tonsillopharyngitis is important to prevent the risk of transmission to others and suppurative and nonsuppurative complications. Aim of the study is to assess the power of strep A optical immunoassay (strep A OIA) and C-reactive protein (CRP) tests in diagnosis of strep throat. Methods: 30 patients presenting with symptoms such as sore throat, high fever, joint pain and headache and having exudative tonsillopharyngitis on ENT examination were included in the study. Two separate throat swabs were taken from all patients for culture and strep A test. Blood specimen was taken for testing CRP and monospot test. Results: Of the 30 patients aged 8-58 with mean age 23.37 +/- 12.74 years, 56% was female, 44% was male. All patients had sore throat, 76.7% headache, 73.3% high fever, 66.7% joint pain, 53.3% cervical lymphadenitis and 33.3% cough. Throat culture was positive for 18 patients and negative for 12 patients. Strep A test had a sensitivity of 94.4% in detecting the presence of strep tonsillopharyngitis, a specificity of 83.3%, a positive predictive value of 89.5% and a negative predictive value of 90.9%. CRP had a sensitivity of 100% in detecting the presence of strep tonsillopharyngitis, a specificity of 41.7%, a positive predictive value of 72.0% and a negative predictive value of 100%. Conclusion: Rapid antigen test is very effective for the determination of group A beta-hemolytic streptococcal tonsillopharyngitis however, it is possible to diagnose streptococcal infection via rapid antigen test without throat culture. Therefore, in out-patient condition; it is assumed that, easy and fast applicable strep A OIA test will improve clinic success and decrease unnecessary antibiotic use. But high cost of this test is the major problem in Turkey. It seems it will take a some period of time for the routine use of these tests. We can assume that there was no streptococcal infection when CRP is negative. If CRP is positive it is obligatory to do throat culture.