Clinical Performance of Check-Direct CPE, a Multiplex PCR for Direct Detection of bla KPC, bla NDM and/or bla VIM, and bla OXA-48 from Perirectal Swabs

ABSTRACT We evaluated the clinical performance of Check-Direct CPE for carbapenemase detection directly from 301 perirectal swabs (258 patients) in a nonoutbreak setting. Culture of a PCR-confirmed, carbapenemase-containing organism, or history of colonization with such organism within the previous 2 weeks, was used as the reference standard. Check-Direct CPE demonstrated a sensitivity value, specificity value, positive predictive value (PPV), and negative predictive value (NPV) of 100% (all bla KPC ), 88%, 21%, and 100%, respectively. False positives accounted for 79% ( n = 34) of samples for which a cycle threshold ( C T ) value was reached. Simulated studies to evaluate specimen pooling as an approach to minimize costs showed no difference in C T values for pooled groups of three or five that each contained a single specimen spiked with ∼1,500 CFU bla KPC Klebsiella pneumoniae; however, the detection rate dropped to 60% at a seeded concentration of ∼150 CFU. When data were pooled, C T values for bla KPC were higher for heavy-feces-containing than for light-feces-containing liquid-suspended specimens. Furthermore, C T values for liquid-suspended specimens were 4 to 5 C T values lower (i.e., represented greater sensitivity) than those seen in direct swab analysis. Culture was equivalent to or better than Check-Direct CPE for 13/15 (87%) isolates tested in a limit-of-detection analysis. Detection of a carbapenemase gene at a C T cutoff value of ≤35 was culture confirmed in 23/24 (96%) of cases; however, C T values of >35 overlapped broadly between culture-positive ( n = 21) and culture-negative ( n = 36) specimens. Check-Direct CPE will likely prove most useful in high-prevalence areas or in outbreak settings where rapid carbapenemase detection is critical for infection control management.