False-positive rapid antigen detection test results: reduced specificity in the absence of group A streptococci in the upper respiratory tract.
Rapid antigen detection tests (ADTs) are promoted for identification of group A streptococci (GAS) in the upper respiratory tract. Although debate persists about their sensitivity, most investigators consider ADTs to be highly specific. Nevertheless, reports continue to describe false-positive ADT results (positive ADT result, negative culture result). This study examined culture results from 522 adult patients with acute pharyngitis and a positive ADT result; unexpectedly, 15% had throat culture results negative for GAS. Normal bacterial flora from 30% of these "negative" culture results produced a positive ADT result. An ADT-reactive organism belonging to the Streptococcus milleri group was isolated from 1 culture; it carried group A carbohydrate antigen. Although S. milleri previously has been associated with false-positive ADT reactions, the frequency of this phenomenon is unknown. The present, large study suggests that false-positive ADT reactions may be more common than previously reported, an observation that must be precisely explained and epidemiologically and clinically defined.
Department of Pediatrics, World Health Collaborating Center for Reference and Research on Streptococci, and Department of Pediatrics, University of Minnesota Medical School, Minneapolism, MN, USA.
D R
DR
Johnson
E L
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Kaplan
D000328:Adult; D000942:Antigens, Bacterial / Q000302:isolation & purification*; D005189:False Positive Reactions; D006801:Humans; D010612:Pharyngitis / Q000382:microbiology*; D011933:Reagent Kits, Diagnostic / Q000382:microbiology*; D012137:Respiratory System / Q000382:microbiology*; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000175:diagnosis / Q000382:microbiology*; D013291:Streptococcus / Q000276:immunology / Q000302:isolation & purification*
D000942:Antigens, Bacterial; D011933:Reagent Kits, Diagnostic