SIBO Does Not Cause Elevated Fecal Calprotectin or Lactoferrin Levels
Small Intestinal Bacterial Overgrowth (SIBO) does not cause elevated fecal calprotectin or lactoferrin levels, as these inflammatory markers remain within normal ranges in patients with SIBO. 1, 2
Evidence on SIBO and Fecal Inflammatory Markers
Studies specifically examining the relationship between SIBO and fecal inflammatory markers have consistently shown:
A 2008 study demonstrated that fecal calprotectin concentrations in patients with SIBO were not significantly different compared to healthy controls (p = 0.907), suggesting no subclinical intestinal inflammatory changes involving neutrophils in SIBO 1
Similarly, a 2011 study in children with SIBO found no statistically significant difference in fecal calprotectin values compared to healthy children (43.0 ± 31.6 mg/kg vs. 35.7 ± 20.7 mg/kg, p = 0.07) 2
Diagnostic Significance of Fecal Inflammatory Markers
According to clinical guidelines, elevated fecal calprotectin and lactoferrin are primarily indicators of intestinal inflammation associated with conditions like inflammatory bowel disease (IBD):
Fecal calprotectin levels are categorized as:
- Normal: <50 μg/g
- Borderline: 50-150 μg/g
- Elevated: >150 μg/g
- Highly elevated: >250 μg/g 3
The American Gastroenterological Association (AGA) suggests using fecal calprotectin >150 mg/g or elevated fecal lactoferrin to rule in active inflammation in ulcerative colitis patients with moderate to severe symptoms 4
These biomarkers reliably differentiate IBD from IBS with specificity and sensitivity exceeding 85% 3
Clinical Implications
When elevated fecal inflammatory markers are detected:
- Consider inflammatory conditions like IBD rather than SIBO
- Elevated markers warrant endoscopic evaluation, especially with moderate-to-severe symptoms 4, 3
- In patients with mild symptoms and elevated inflammatory markers, the AGA suggests endoscopic assessment rather than empiric treatment 4
Diagnostic Approach When Suspecting SIBO
If SIBO is suspected but fecal inflammatory markers are elevated:
- Consider alternative or concurrent diagnoses, particularly inflammatory conditions
- Hydrogen/methane breath testing remains the primary diagnostic tool for SIBO
- Elevated fecal calprotectin or lactoferrin should prompt investigation for other inflammatory conditions, as these elevations are not characteristic of SIBO alone
Common Pitfalls
- Misattributing elevated inflammatory markers to SIBO when another inflammatory condition may be present
- Failing to investigate for IBD or other inflammatory conditions when fecal calprotectin or lactoferrin are elevated
- Assuming normal fecal inflammatory markers rule out all intestinal pathology (they specifically indicate absence of neutrophil-mediated inflammation)
In conclusion, while SIBO can cause various gastrointestinal symptoms, it does not typically result in the neutrophil-mediated inflammation that would elevate fecal calprotectin or lactoferrin levels. If these markers are elevated, clinicians should consider other inflammatory conditions as the cause.