Comparison of two rapid Streptococcus pyogenes diagnostic tests with a rigorous culture standard.
BACKGROUND
Comparisons of rapid antigen tests for the diagnosis of pharyngitis are often made between published studies but may not be reliable given differences in study design, sampling and reference standard definitions. Tests are rarely compared against each other in a single study.


METHODS
The sensitivity and specificity of two rapid diagnostic tests were compared against a multiplate culture standard defined as the identification of on any of four culture plates. Paired swabs were tested for antigen using Genzyme's OSOM Ultra Strep A Test and compared with Biostar's Strep A OIA Max Test.


RESULTS
Ninety-four (31.1%) of 302 matched samples were identified with The sensitivity of Genzyme's OSOM Ultra Strep A Test against the multiplate culture standard was 92.6%, significantly higher ( P= 0.001) than that (75.5%) of Biostar's Strep A OIA Max Test. Specificities were 92.8 and 97.1%, respectively. Data analysis of culture results and statistical modeling showed that cultures of two or more samples are necessary for a sensitivity of 95% or greater for a comparison standard compared with true disease status.


CONCLUSIONS
When comparing the performance of rapid antigen tests for pharyngitis, a rigorous culture standard should be used consisting of at least two separate samples (swabs and/or pledgets), ultimately plated on selective agar. Genzyme's OSOM Ultra Strep A Test was significantly more sensitive than Biostar's Strep A OIA Max Test in comparison with a multiplate culture standard and a same swab, single plate culture standard.
Gieseker
Karen E
KE
Department of Epidemiology, The Children's Hospital, and the Department of Preventive Medicine, University of Colorado Health Sciences Center, Denver, CO, USA.
Mackenzie
Todd
T
Roe
Martha H
MH
Todd
James K
JK
D000942:Antigens, Bacterial / Q000032:analysis*; D001431:Bacteriological Techniques; D002675:Child, Preschool; D015169:Colony Count, Microbial; D003470:Culture Media / Q000592:standards*; D005260:Female; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008297:Male; D009305:Nasopharynx / Q000382:microbiology*; D010612:Pharyngitis / Q000175:diagnosis / Q000382:microbiology; D011336:Probability; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000175:diagnosis; D013297:Streptococcus pyogenes / Q000276:immunology* / Q000302:isolation & purification*; D013997:Time Factors
D000942:Antigens, Bacterial; D003470:Culture Media