Accuracy and reproducibility of a four-hour method for anaerobe identification

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Abstract
In this study, the ability of a 4-h enzyme assay kit system, the RapID ANA method, to accurately and reproducibly identify a spectrum of clinically significant anaerobic bacteria was evaluated in 2 separate USA institutions. Additional tests were performed as required. Of a total of 188 organisms tested at Hershey Medical Center (HMC, Hershey, Pennsylvania), 86.2% were correctly identified to species level without additional tests, 5.9% required extra tests for correct identification, and 8.0% were misidentified. Of 53 strains tested at Johns Hopkins Hospital (JHH, Baltimore, Maryland), 52.8% were correctly identified without extra tests, 28.3% required extra tests for correct identification, and 18.9% were misidentified. Of 21 organisms tested at both institutions, those tested at JHH required additional tests for correct identification in 38.1% of cases, compared with 9.5% at HMC. Misidentification rates were identical (9.5%) in both centers. Of strains tested at HMC only, 86.8% were correctly identified without extra tests, 5.4% were identified with additional tests, and 7.8% were misidentified: corresponding data for JHH were 53.1, 21.9 and 25.0%, respectively. Of 53 strains tested in triplicate at JHH, 56.7% yielded the same result on each occasion, 37.7% were identical in 2 of 3 tests, and 5.7% gave different results on each of 3 occasions. Discrepancies between identification rates at HMC and JHH may be explained by differences in species tested (more commonly encountered species were tested at HMC) and interpretation of reactions by the 2 different readers. The RapID ANA method has the potential for rapid identification of clinically isolated anaerobes; however, accuracy and reproducibility may vary as a function of the specific laboratory setting.