Although stool has long been the standard specimen type when testing for gastrointestinal (GI) pathogens, rectal swabs could be an equal, if not superior, collection method. The use of multiplex molecular methods that add sensitivity for both viral and bacterial detection has been growing rapidly, but there is a remaining question as to whether sample type could have an impact on pathogen detection. In this study, we evaluated the effect of different sample types (stool versus rectal swabs) on the detection rate of GI pathogens in samples submitted for testing.
Data mining was conducted on specimens (n=13822) submitted to a reference laboratory. Multiplex TEM-PCR™ GI panel that included 8 bacterial, 3 viral, and 2 protozoan targets was used for detection. Both sexes and all age groups were represented, but the pediatric patient population comprised 42% of specimens (n= 5765). The Wilcoxon rank sum test with continuity correction was used to determine the statistical significance of observations obtained and the assessment of significance was at a P value of <0.05.
Adenovirus, Norovirus, Rotavirus and enteropathogenic Escherichia coli were detected more often from rectal swabs compared to stool specimens for all age groups. In contrast, a higher detection rate of enteroinvasive E. coli and the shiga-like toxin gene was found in stool specimens. Thirty nine percent of tested samples (n=5367) had at least one pathogen present in both sample types. The Clostridium difficile toxin B gene was the most prevalent target with a detection rate of 36%, which may be attributed to the high percentage of pediatric patients in the database. Rectal swabs performed significantly better for multiple pathogen detection, but there were no differences between rectal swabs and stool specimens for detected single targets.
Proper sample collection is essential for the accurate diagnosis of infectious diseases. While time delay in sample acquisition and transport conditions for stool may affect test results, rectal swabs can be administered at the point of care and serves as a rapid collection technique. The combination of sample collection (such as flocked rectal swabs) with multiplex molecular diagnostics methods may facilitate the detection of GI pathogens in the clinical environment.
E. Grigorenko, Diatherix lab: Investigator , Salary
R. Ward, Diatherix Laboratories, Inc: Employee , Salary