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 diagnostic methods are 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 the 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 University Hospital, FMUSP, between May 2001 and April 2002, were submitted to two simultaneous collections of oropharyngeal material using swabs. 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 studied patients, the rapid test was positive in 56% and negative in 44%. GAS growth in culture was observed for 40.7% of the patients. The 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 the high sensitivity of the test permits its use for the identification of patients with GAS. Rapid streptococcal antigen detection tests have been shown to be an important supporting tool in the etiologic diagnosis of pharyngotonsillitis.
Araujo Filho
Bernardo Cunha
BC
SBORL, Brazil. bcaf@terra.com.br
Imamura
Rui
R
Sennes
Luiz Ubirajara
LU
Sakae
Flávio Akira
FA
D000293:Adolescent; D000328:Adult; D000368:Aged; D000942:Antigens, Bacterial / Q000276:immunology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010612:Pharyngitis / Q000175:diagnosis / Q000382:microbiology*; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000175:diagnosis* / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000276:immunology*; D014069:Tonsillitis / Q000175:diagnosis / Q000382:microbiology*
D000942:Antigens, Bacterial