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Optical immunoassay for rapid detection of group A beta-hemolytic streptococci. Should culture be replaced?
T A Schlager1, G A Hayden, W A Woods
1Department of Pediatrics, University of Virginia Medical Center, Charlottesville, USA.
Objective:
To evaluate an optical immunoassay rapid antigen test to detect group A beta-hemolytic streptococci directly from throat swab specimens.
Design:
Criterion standard with "blinded" comparison. Double-swab pharyngeal samples were obtained; one swab was cultured and the other was used for the rapid antigen test.
Setting:
Microbiology laboratory in a primary care center at a university teaching hospital.
Patients:
Two hundred sixty-two outpatients with pharyngitis.
Main Outcome Measure:
The results of the optical immunoassay rapid antigen test were compared with results of standard aerobic culture.
Results:
Sixty-two (24%) of 262 samples were culture-positive; 48 of these 62 were positive by the optical immunoassay rapid test (sensitivity, 77%). Of the 200 culture-negative samples, seven (4%) were positive by the rapid test (specificity, 96%).
Conclusion:
The optical immunoassay performed well, but like other rapid tests, is not sensitive enough to replace standard culture for detection of group A beta-hemolytic streptococci.