Reliability of microbiological tests in the diagnosis of Clostridium difficile infection

Abstract

The aim of the study was to analyze the characteristics {sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and credibility} of tests for microbiological diagnosis of infections caused by Clostridium (C. difficile). The research was done at the Public Health InstituteNiš, the Center for Microbiology during the period 2016-2019. The study included 25 patients with Clostridium difficile infection (CDI) (25 fecal samples) and 50 patients with diarrhea who were not diagnosed with CDI (50 faecal samples). The samples were examined by various tests for the detection of toxin in the stool and with two tests to prove the produced glutamate dehydrogenase enzyme -GDH. RIDA GENE Clostridium difficile test (Real Time Multiplex PCR, R-Biofarm, Damstadt, Germany) was used as a reference test.Among the examined tests, the highest sensitivity in toxin detection was the ELISA-ridascreen C. difficile Toxin A / B (R -Biopharm AG, Darmstadt, Germany) (88%, PPV = 85.71%, NPV = 97.87%) and the lowest C. difficile TOXIN A& B -CHEK-1 (VEDALAB, ALENCON CEDEX, France) (68%, PPV = 85%, NPV = 85.45%). All toxin detection tests had a high specificity that was not less than 92%. In detecting the GDH antigen, the Rida ® QUICK C. difficile GDH test (R -Biopharm AG, Darmstadt, Germany) showed better performance (sensitivity 100%, specificity 92%, PPV = 89.28%, NPV = 100% and authenticity 94.66% ).The results of the research conducted in Niš showed high values of the characteristics for certain toxindetecting tests in feces (sensitivity up to 88%, specificity to 98%, etc.). Research results in other studieshave shown that the values of the parameters that determine the characteristics of the tests are lower by 10% -20%, although there is a study whose results are consistent with ours. The reasons for relatively high values should be sought in strict selection criteria for samples that are close to criteria present in factory conditions when designing such tests.O r i g i n a l a r t i c l e 344 Acta facultatis medicae Naissensis 2019; 36(4):343-355 Although the results of this study confirm that there is no ideal diagnostic test in the microbiological diagnosis of CDI, the high sensitivity, specificity, PPV and NPV values make GDH tests suitable for the first screening of sample stools in everyday work.