From the Guidelines
No, colonic washing is not recommended as a specimen for the Glutamate Dehydrogenase (GDH) test. The GDH test is specifically designed to detect Clostridioides difficile (C. difficile) infection using fresh, unformed stool samples 1. Colonic washings would likely be too diluted and may contain substances that interfere with the test's accuracy. The GDH test works by detecting an enzyme produced by both toxigenic and non-toxigenic strains of C. difficile, and proper specimen collection is crucial for reliable results.
For accurate C. difficile testing, a fresh stool sample (collected within 2 hours of testing or refrigerated for up to 72 hours) should be submitted. The sample should be unformed or liquid, as formed stool may contain lower bacterial loads. Using inappropriate specimens like colonic washings could lead to false negative results, potentially missing cases of C. difficile infection, or false positive results that could lead to unnecessary treatment.
Some key points to consider when testing for C. difficile include:
- The diagnosis of CDI should be suspected in patients with acute diarrhea (≥ 3 loose stools in 24 h) with no obvious alternative explanation 1
- Stool testing should only be performed on diarrheal stools from at-risk patients with clinically significant diarrhea 1
- Nucleic acid amplification tests (NAAT) for C. difficile toxin genes appear to be sensitive and specific and may be used as a standard diagnostic test for CDI 1
- GDH screening tests for C. difficile are sensitive but do not differentiate between toxigenic and non-toxigenic strains, and may be used in association with toxin A/B enzyme immunoassays (EIA) testing 1
It is essential to follow the recommended guidelines for specimen collection and testing to ensure accurate diagnosis and effective management of C. difficile infection.
From the Research
Colonic Washing as a Specimen for GDH Test
- There is no direct evidence in the provided studies to support the use of colonic washing as a specimen for the Glutamate Dehydrogenase (GDH) test.
- The studies primarily focus on the use of stool samples, rectal swabs, and fecal samples for the diagnosis of Clostridium difficile infection using various tests, including GDH testing 2, 3, 4, 5, 6.
- However, it can be inferred that the GDH test is typically performed on stool samples, and the use of alternative specimens like rectal swabs has been explored in some studies 3, 4.
- The study by 4 evaluated the use of rectal swabs for the detection of C. difficile and found that dry swabs were a suitable alternative to stool samples for PCR-based detection, but the liquid transport medium used with the swabs had lower sensitivity.
- Another study by 5 found that testing of fecal samples for GDH can be useful as a negative screening method, and the results of this test show high correlation with culture.
- Overall, while there is no direct evidence to support the use of colonic washing as a specimen for the GDH test, the existing research suggests that alternative specimens like rectal swabs may be explored for diagnostic purposes, but their performance characteristics should be carefully evaluated 3, 4.