Role of rapid antigen detection test for the diagnosis of group A beta-hemolytic streptococcus in patients with pharyngotonsillitis.
Group A beta-hemolytic streptococcus (GAS) is an important pharyngotonsillitis etiologic agent. Correct etiologic diagnosis and early treatment prevent suppurative and non-suppurative complications of streptococcal pharyngotonsillitis; however, clinical diagnosis is not reliable. Within this context, rapid detection methods of GAS antigen are useful to diagnose this agent.


OBJECTIVE
The objective of the present study was to determine sensitivity and specificity of rapid GAS antigen detection tests used in Brazil.


METHODS
Clinical prospective.


METHODS
Eighty-one patients with clinical diagnosis of acute pharyngotonsillitis seen at the otorhinolaryngology emergency department of the University Hospital, FMUSP, between May 2001 and April 2002 were submitted to two simultaneous collections of oropharyngeal material using swabs. The rapid GAS antigen detection test was compared to culture on blood agar, the gold standard for the diagnosis of this etiologic agent.


RESULTS
Among the 81 patients studied, the rapid test was positive in 56% and negative in 44%. GAS growth in culture was observed in 40.7% of the patients. Sensitivity and specificity of the rapid test were, respectively, 93.9% and 68.7%, and the negative and positive predictive values were 94.2 and 67.4%, respectively.


CONCLUSIONS
We concluded that high sensitivity of the test allows its use in the identification of patients with GAS. Rapid streptococcal antigen detection tests have been shown to be an important adjuvant tool in the etiologic diagnosis of pharyngotonsillitis.
Araujo Filho
Bernardo Cunha
BC
Division of Clinical Otorhinolaryngology, Hospital das Clínicas, Medical School, University of Sao Paulo, Sao Paulo, SP.
Imamura
Rui
R
Sennes
Luiz Ubirajara
LU
Sakae
Flávio Akira
FA
D000293:Adolescent; D000328:Adult; D000368:Aged; D000942:Antigens, Bacterial / Q000302:isolation & purification*; D001431:Bacteriological Techniques; D005260:Female; D006801:Humans; D007159:Immunologic Tests; D008297:Male; D008875:Middle Aged; D010612:Pharyngitis / Q000382:microbiology*; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections; D013297:Streptococcus pyogenes / Q000276:immunology*; D014069:Tonsillitis / Q000175:diagnosis / Q000382:microbiology*
D000942:Antigens, Bacterial