1091. Algorithmic Release of Clostridium difficile PCR Results From a Multiplex Gastrointestinal (GI) Panel in Children <3 Years Old

Abstract

BackgroundInfants have a high rate of asymptomatic Clostridium difficile (CD) colonization, up to 37%. Given this, our laboratory does not release CD+ results from the BioFire FilmArray Gastrointestinal Panel (FGP) in patients <3 years, unless requested by a physician. We sought to validate this model by comparing results from FGP to semi-quantitative CD PCRs for toxin B and glutamate dehydrogenase (GDH), enzyme immunoassay (EIA) for toxin A/B/GDH, and physician requests for CD results.MethodsRetrospective analysis of children <3 years with GI illness and FGP CD+ results between September 2016 and April 2018. CD PCRs for toxin B and GDH, CD EIA for toxin A/B/GDH were performed on convenience samples of frozen aliquots in Cary Blair. Physician request for release of CD results was used as a surrogate of possible role of CD on GI illness.ResultsOf 5,990 FGP, 2,267 (38%) were in children <3 years: 619 (27%) were CD+. Of these 619, 602 (97%) were not reported per algorithm. 62% (386/619) of CD+ samples had copathogens detected; enteropathogenic Escherichia coli and norovirus most frequently. For CD PCRs and EIA performed in subset of 49 CD+, mean cycle threshold values (Cts) for toxin B were evaluated (Table 1). Of 48 samples with detectable CD by toxin B PCR, 14 (29%) had both GDH and toxin B detected, 24 (51%) had only GDH detected, and 9 (19%) had neither GDH nor toxin B detected.ConclusionOnly 3% of FGP CD results in children <3 years were released per physician request, suggesting limited clinical significance. A copathogen was detected in 62% of CD+ samples that may explain illness. Among evaluable samples, only 28.6% of CD+ had both GDH and toxin detected by EIA, possibly indicating low specificity of CD PCR. Ongoing testing and prospective studies are warranted to determine the validity of our algorithm and if semi-quantitative PCR or EIA can be useful to identify when CD detection by FGP in children <3 years is clinically significant.Table 1: CD Toxin B PCR Ct Values Compared with FGP Result Release, Co-Pathogen Detection, and EIA ResultsMedian CtMedian Ct P-valueFGP-CD+ result released (n = 1)20.64FGP-CD+ result not released (n = 47)28.77NSFGP-CD+ only(n = 24)26.83Co-pathogen(n = 24)29.34NSEIA toxin+(n = 14)23.23EIA toxin−(n = 34)31.110.0005Disclosures A. Leber, Nationwide Children’s Hospital: Research Contractor, Research support.