Pre-analytical and post-analytical evaluation in the era of molecular diagnosis of sexually transmitted diseases: cellularity control and internal control

Background. A national project on Clostridium difficile infection (CDI), funded by the Center for Prevention and Control of Diseases of Italian Ministry of Health, was performed in 2012-2013. Microbiological laboratories of the National Public Heath System were invited by the Istituto Superiore di Sanità to provide information on CDI diagnostics through a closed answer questionnaire.
Materials and Methods. In total, 14 regions and the independent province of Trento participated in and 278 filled questionnaires were sent back. The data obtained indicate that 87% of the laboratories routinely perform diagnostic assays for C. difficile. GDH detection is used as the first screening test by 33% of these laboratories. Most of them declared to use toxins enzyme immunoassays (88%), whereas a minority performs C. difficile culture (26%) or molecular assays (19%). Only 37% of the laboratories stated to adopt a diagnostic algorithm. The algorithms adopted are different and high heterogeneity in the combination of the assays used was observed.
Results. Fifty eight percent of laboratories declared to type C. difficile strains, the majority (82%) sending faecal samples or strains to a reference laboratory. Sixty-two laboratories, routinely performing C. difficile culture, were invited by ISS to send five isolates for molecular typing. In total, 103 isolates from 22 hospitals were collected and 31 different PCR-ribotypes were identified. PCR-ribotype 356/607 was the most frequent (27%), followed by 018 (12%) and 027 (8%). The latter is a worldwide spread hypervirulent type only recently emerged in our country. A molecular characterization of the different PCR-ribotypes detected was also performed by Xpert® C. difficile.
Conclusions. The study highlights the need for a more careful selection of diagnostic algorithms to improve CDI diagnosis and the urgency to implement a National Surveillance of CDI in Italy.