RESUMEN
OBJECTIVE: To compare the sensitivity of five group A streptococcal antigen detection systems and single blood agar plate culture with a two-plate culture method for diagnosis of streptococcal pharyngitis. DESIGN: Two simultaneous throat swabs were obtained from consecutive patients with suspected streptococcal pharyngitis. One swab was tested for streptococcal antigen by physicians' office nurses and the other was cultured on both aerobic blood agar and anaerobic trimethoprim-sulfamethoxazole blood agar plates. SETTING: Community office practice and community hospital laboratory. PARTICIPANTS: Consecutive outpatients seen by one of four pediatricians or a family practice physician. MAIN OUTCOME MEASURES: Results of rapid streptococcal antigen tests were compared with culture results either on a single aerobic blood agar plate or on the two-plate culture method. RESULTS: On throat swabs from 755 consecutive outpatients, the two-plate culture method detected 261 cases (defined as 100%) of group A streptococcal pharyngitis. The anaerobic trimethoprim-sulfamethoxazole plate alone, read at 1 and 2 days, detected 245 cases (94%). The blood agar plate used alone detected 189 cases (72%) at 2 days and 151 cases (58%) at 1 day. Antigen detection test results were positive for 106 throat specimens (41%), with individual kit sensitivity ranging from 31% to 50% compared with the two-plate culture method. Antigen detection test sensitivity decreased with decreasing colony counts. Antigen kit false-positivity rates varied from 0 to 28%. CONCLUSIONS: We conclude that the single blood agar plate culture and the antigen detection tests are insensitive, possibly leading the physician toward undertreatment and risking immunologic, local, or distant sequelae. The two-plate culture method should be the standard of practice to rule out streptococcal pharyngitis.
Asunto(s)
Antígenos Bacterianos/análisis , Faringitis/diagnóstico , Juego de Reactivos para Diagnóstico , Infecciones Estreptocócicas/diagnóstico , Streptococcus/inmunología , Niño , Medios de Cultivo , Humanos , Faringitis/microbiología , Sensibilidad y Especificidad , Manejo de EspecímenesRESUMEN
Forty-three consecutive cases from a community hospital with concomitant bone marrow iron stain, serum ferritin, and erythrocyte sedimentation rate (ESR) were reviewed. Cases were classified as iron present or absent by the bone marrow iron stain. A two-dimensional linear graphic relationship between ferritin and ESR correctly identified six of nine iron-deficient patients and 32 of 34 iron-present patients. Four cases yielded indeterminate results. One complex iron-deficient case was incorrectly classified. This graphic method developed with data from tertiary care patients was correct in 88.4% of cases, incorrect in 2.3%, and indeterminate in 9.3%. When absent iron stores were graphically predicted, the predictive value was 100%. When iron deficiency was graphically excluded, the predictive value was 97%. The authors conclude the graphic method is useful in a community hospital practice for the confirmation or exclusion of iron deficiency.