From the Guidelines
No, lactulose cannot be used to test for Clostridioides difficile (C. diff) infection. The appropriate diagnostic tests for C. diff include enzyme immunoassays (EIAs) for C. diff toxins, glutamate dehydrogenase (GDH) antigen testing, nucleic acid amplification tests (NAATs) that detect toxin genes, or toxigenic culture 1. Lactulose is actually a medication used to treat constipation and hepatic encephalopathy; it has no diagnostic value for C. diff infections. When C. diff infection is suspected based on symptoms like watery diarrhea, abdominal pain, and fever, especially following antibiotic use, proper stool sample collection and submission for one of the approved testing methods is required. Using inappropriate testing methods like lactulose could delay proper diagnosis and treatment, potentially allowing the infection to worsen.
Some key points to consider in the diagnosis of C. diff infection include:
- The diagnosis should be based on clinical signs and symptoms in combination with laboratory tests 1
- Stool testing should only be performed on diarrheal stools from at-risk patients with clinically significant diarrhea (≥ 3 loose stools in 24 h) with no obvious alternative explanation 1
- Nucleic acid amplification tests (NAATs) for C. difficile toxin genes appear to be sensitive and specific and may be used as a standard diagnostic test for CDI 1
- Glutamate dehydrogenase (GDH) screening tests for C. difficile are sensitive but do not differentiate between toxigenic and non-toxigenic strains 1
The most recent and highest quality study on this topic is from 2019, which recommends the use of NAATs or a multistep algorithm including GDH and toxin testing for the diagnosis of C. diff infection 1. Another study from 2018 also supports the use of NAATs or a multistep algorithm for diagnosis, and highlights the importance of proper stool sample collection and submission for testing 1.
In terms of the quality of evidence, the 2019 study provides high-quality evidence for the diagnosis of C. diff infection, with a systematic review and meta-analysis of 238 studies 1. The 2018 study also provides high-quality evidence, with a systematic review and meta-analysis of 1416 patients 1.
Overall, the evidence suggests that lactulose is not a suitable test for C. diff infection, and that proper diagnostic testing using approved methods is essential for accurate diagnosis and treatment. The use of lactulose for diagnostic purposes is not recommended, and may lead to delayed or inappropriate treatment, potentially worsening patient outcomes.
From the Research
Testing for C. diff with Lactulose
- The provided studies do not directly address the use of lactulose for testing Clostridioides difficile (C. diff) infection 2, 3, 4.
- However, lactulose is mentioned in the context of assessing gut health and intestinal permeability 5, 6.
- The lactulose:mannitol test is used to evaluate gut health, but its utility is questioned due to the correlation between lactulose and mannitol absorption, suggesting that lactulose alone may be as informative as the lactulose:mannitol test 5.
- The lactulose breath hydrogen test is used to diagnose small intestinal bacterial overgrowth, but its sensitivity and specificity are poor, and it is not a reliable method for diagnosing this condition 6.
- There is no direct evidence to support the use of lactulose as a test for C. diff infection, and other diagnostic methods such as stool tests or endoscopy may be more appropriate 2, 3, 4.