Molecular Panels for Identifying Etiology with Acute GI Symptoms

A recent study (MR Nicholson et al. J Pediatr 2016; 176; 50-6) examined the use of multiplex molecular testing to determine the etiology of acute gastroenteritis in children.  It is interesting that little has been published about this increasingly common practice of sending a 12 to 15 panel PCR assay when faced with acute GI symptoms, mainly diarrhea.

This study was a prospective population-based study of children <6 years with acute gastroenteritis (2008-2011).

Findings:

  • 70.4 % (152/216) samples tested positive for a pathogen, with norovirus the most frequent (n=78, 36.1%). Clostridium difficile was next at 16.2% (n=35).
  • 22.7% (n=49) tested positive for more than 1 pathogen including 25 with a C difficile detection
  • In this study, the authors noted C difficile colonization in 8% of healthy children aged 0-51 months and in 14% of children <12 months

Implications of this study and this technology:

  • Prior to this technology, traditional approaches typically identified less than 15% of the cases of acute gastroenteritis.  Thus, this new technology increases the likelihood of a definitive diagnosis.
  • Multiple pathogens, particularly with C difficile, illustrate how this new technology will present some difficulties with interpretation.  C difficile has very high rates of colonization in infants (anywhere from 25-80%) without AGE symptoms and lower rates of colonization in toddlers.  High colonization/detection has been noted in inflammatory bowel disease patients (17%) and pediatric oncology patients (30-55%).
  • For C difficile, molecular testing is much less likely to correlate with clinical disease than toxin-based assays. “A recent study in adults found that virtually all CDI-related complications occurred in patients with a positive toxin immunoassay.” (JAMA Intern Med 2015; 175: 1792-801)

My take: These panels are helpful in identifying infectious etiologies of AGE and may help prevent unnecessary endoscopic procedures.  Due to their limitations, careful selection of which patients to test and cautious interpretation of the results are needed.

Related blog posts:

Sunset from Bar Harbor, ME

Sunset from Bar Harbor, ME

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