Diagnostic accuracy of 16S ribosomal RNA gene polymerase chain reaction in bacteremia: A prospective observational study
The standard method for diagnosing bacteremia is blood culture. However, the sensitivity of blood culture is low when the number of bacteria in the blood is low or when antibiotics have already been administered. Furthermore, some bacteria are difficult to detect in blood cultures. 16S ribosomal RNA (rRNA) contains conserved sequences that are targeted for PCR amplification using universal primers. We investigated whether the threshold cycle (Ct) value of 16S rRNA real-time PCR in whole-blood samples can be used for early diagnosis of bacteremia. Ct values of the 16S rRNA real-time PCR in 307 collected specimens showed a bimodal distribution. Ct values of the blood culture-positive group were significantly lower than those of the blood culture-negative group (P < 0.001). The cutoff value of the receiver operating characteristic curve was 38.80, as determined using finite-mixture modeling and expectation-maximization algorithm. Analysis of the diagnostic accuracy at this cutoff value showed a sensitivity of 91.4%, specificity of 33.5%, positive predictive value of 15.0%, and negative predictive value of 96.8%. The Ct value of 16S rRNA real-time PCR shows high negative predictive value, it may be useful for excluding bacteremia when the cutoff value is set appropriately.