Performance of two tube coagulase methods for rapid identification of Staphylococcus aureus from blood cultures and their impact on antimicrobial management

Test parameters and clinical impact of the direct tube coagulase test (DTCT) for rapid identification of Staphylococcus aureus from blood culture were investigated. The sensitivity of the DTCT at 4 h using saline dilution was 96%, compared with 93% using serum separator tubes; specificity was 100% for both methods. Among 32 patients with S. aureus bacteraemia, treatment modifications were based on microbiology results from the primary source of infection in 12 patients, on a Gram's stain from blood culture in seven patients, and on the DTCT in nine patients. The DTCT is a valuable adjunct in the routine microbiology laboratory because of its good performance, technical simplicity and low cost.