T2Bacteria Panel Detects and Identifies Bloodstream Infections

Bloodstream infections can be accurately distinguished or excluded within a 4- to 8-hour timeframe using the T2Bacteria Panel, according to a study published in the Annals of Internal Medicine. Results from T2Bacteria compared favorably with blood culture results.

This prospective multicenter study included 1427 patients in 11 American hospitals who received blood cultures between December 2015 and August 2017. Intervention consisted of a comparison between T2Bacteria Panel testing and blood cultures in terms of diagnosing bloodstream infections categorized as proven, probable, and possible. Primary outcomes included the T2Bacteria Panels’ specificity and sensitivity. The results for 5 targeted organisms [Enterococcus faecium Staphylococcus aureus Klebsiella pneumoniae Pseudomonas aeruginosa] within the panel determined a positive or negative outcome in per-patient analyses, while separate results for each organism were used for per-assay analyses. Results for T2Bacteria-detected organisms were designated concordant or discordant.

Of the study population, 3% (n=39) received positive blood culture results and 13% (n=181) received positive T2Bacteria results. Mean time to species identification were significantly shorter for T2Bacteria (3.61±0.2 hours for 1 sample to 7.70±1.38 hours for 7 samples) vs blood culture (71.7±39.3 hours). Mean time to positivity with blood cultures was 38.5±32.8 hours.

T2Bacteria showed a per-patient sensitivity of 90% (95% CI, 76-96%) and specificity of 90% (95% CI, 88-91%) for proven bloodstream infections, with a negative predictive value of 99.7% (1242 out of 1246). Positive T2Bacteria results with negative blood cultures occurred in 10% (n=146) of cases, with 60% of these results categorized as possible (n=26) or probable (n=62) bloodstream infections. Using a negative blood culture as the gold-standard for the absence of bloodstream infection caused by T2Bacteria-targeted pathogens, the per-assay specificity was 98% (95% CI, 97-98%); the per-patient specificity was 94% assuming probable infections to be positives, and 96% assuming probable and possible infections to be positives.

Limitations to this study included a low rate of positive blood cultures, the use of just one set of culture specimens, and a lack of detection of nontargeted pathogens by the T2Bacteria Panel.

The study authors concluded that “T2Bacteria may improve management of [bloodstream infections] and sepsis by providing results more rapidly than blood cultures and identifying some pathogens that are missed by blood cultures.” Researchers also highlighted that the T2Bacteria Panel may be useful if used in conjunction with blood and nonblood cultures and results are interpreted with reference to patients’ clinical status and antibiotic use. “To date, T2Bacteria and T2Candida are the only culture-independent tests cleared by the FDA for direct detection of multiple bacteria and fungi in whole blood.”

This study was funded by T2 Biosystems. Authors report associations with T2 Biosystems and with pharmaceutical companies.

Reference

Nguyen MH, Clancy CJ, Pasculle AW, et al. Performance of the T2Bacteria Panel for diagnosing bloodstream infections [published online May 13, 2019]. Ann Intern Med. doi:10.7326/M18-2772