Advice

Summary

Summary

Xpert Carba‑R is a qualitative in vitro diagnostic test that detects organisms that have carbapenemase genes and differentiates between the 5 most prevalent carbapenemase gene families. Three diagnostic accuracy studies were identified involving a total of 990 clinical bacterial isolates and faecal samples. One study reported an overall test sensitivity of 94%. Reported test results for individual carbapenemase genes ranged from 71% to 100% for sensitivity, 77% to 99% for specificity and 81% to 93% for positive predictive values. Negative predictive values were only reported in 2 studies, but both reported a value of 100%. The Xpert Carba‑R test must be run on the GeneXpert molecular diagnostic system, which costs between £18,077 and £121,308 depending on the module configuration, excluding VAT. Each single‑test Xpert Carba‑R cartridge costs £30, excluding VAT.

Product summary and likely place in therapy

  • The Xpert Carba‑R test is a qualitative in vitro diagnostic test used to detect colonisation with carbapenemase‑producing organisms. It detects and differentiates the 5 most prevalent carbapenemase gene families: KPC, NDM, VIM, IMP‑1 and OXA‑48 (including the OXA‑181 and OXA‑232 variants of OXA‑48).

  • The Xpert Carba‑R test would be used in place of standard culture‑based tests and as an adjunct to supplementary and confirmatory tests such as antimicrobial resistance testing. This would guide local infection control protocols for preventing transmission to other susceptible people.

Accuracy and effectiveness

  • The published evidence summarised in this briefing comes from 3 studies including a total of 990 clinical bacterial isolates and faecal samples.

  • One diagnostic accuracy study used a panel of 450 clinical bacterial isolates to compare the sensitivities of 3 commercial assays. The sensitivity of Xpert Carba‑R for each carbapenemase gene ranged from 71% to 100%. The overall test sensitivity was reported as 94%.

  • One diagnostic accuracy study used 394 rectal, peri‑rectal and stool samples to determine the performance characteristics of Xpert MDRO, an earlier version of Xpert Carba‑R. The negative predictive values and sensitivities for Verona integron‑encoded metallo‑beta‑lactamase (VIM) and Klebsiella pneumoniae carbapenemase (KPC) genes were 100%.

  • One diagnostic accuracy study used 120 clinical bacterial isolates and 26 faecal samples and reported the negative predictive value and sensitivity of Xpert Carba‑R as 100%.

Technical and patient factors

  • The Xpert Carba‑R test detects bacterial DNA from a rectal swab specimen.

  • Results are available in about 50 minutes.

  • The test can be done in any healthcare setting with access to the GeneXpert system.

Cost and resource use

  • Each single‑test Xpert Carba‑R cartridge costs £30, excluding VAT. The GeneXpert system, needed to run the test, costs between £18,077 and £121,308 depending on configuration, excluding VAT.

  • One conference abstract with limited evidence on resource consequences for Xpert Carba‑R reported that the cost of reagents plus technical time was approximately £35 per test, compared with £75 for the standard culture with PCR test.