To evaluate whether the implementation of a multiplex gastrointestinal pathogen panel (GIP) was associated with changes in Clostridioides difficile (C difficile) testing and detection rates.

We conducted an observational study using interrupted time series analysis and included pediatric patients with testing capable of detecting C difficile. From 2013 to 2015 (“conventional diagnostic era”), stool testing included C difficile-selective polymerase chain reaction and other pathogen-specific tests. From 2015 to 2017 (“GIP era”), C difficile polymerase chain reaction was available along with the GIP, which detected 22 pathogens including C difficile, and replaced the need for additional tests. Outcomes included C difficile testing and detection rates in ambulatory, emergency department, and inpatient settings.

There were 6841 tests performed and 1214 C difficile positive results. Across the 3 settings, GIP era had significantly higher C difficile testing (1.7-2.3 times higher) and C difficile detection rates (1.9-3.4 times higher) compared with conventional diagnostic era. After adjusting for the number of tests performed, detection rates were no longer significantly different. Of C difficile positive GIPs, 31% were coinfected with another organism. With GIP testing, patients 1 year of age had a significantly higher C difficile percent positivity than 2-year-old (P = .02) and 3- to 18-year-old children (P < .01). Younger children with C difficile were more likely to be coinfected (P < .01).

Introducing a multiplex panel led to increased C difficile testing, which resulted in increased C difficile detection rates and potential identification and treatment of colonized patients. This highlights an important target for diagnostic stewardship and the challenges associated with multiplex testing.