Can Small Intestine Bacterial Overgrowth (SIBO) cause elevated fecal calprotectin and lactoferrin levels?

Can SIBO Cause Elevated Fecal Calprotectin and Lactoferrin?

Small Intestinal Bacterial Overgrowth (SIBO) can cause elevated fecal calprotectin and lactoferrin levels in some patients, but the evidence is mixed and inconsistent. The relationship between SIBO and these fecal inflammatory markers varies significantly across different patient populations and clinical contexts.

Evidence on SIBO and Fecal Inflammatory Markers

Systemic Sclerosis Patients

In patients with systemic sclerosis, there is a strong correlation between SIBO and elevated fecal calprotectin levels:

• A 2015 study found a marked association between abnormal fecal calprotectin levels and the presence of SIBO 1
• Levels ≥275 μg/g were strongly associated with SIBO (sensitivity 93%, specificity 95%) 1
• Eradication of SIBO in these patients led to significant decreases in fecal calprotectin levels 1

Pediatric Populations

In contrast, pediatric studies show different results:

• A 2011 study found no significant difference in fecal calprotectin levels between children with SIBO and healthy controls 2
• Median values were 36.0 mg/kg in SIBO patients vs. 29.5 mg/kg in healthy controls (p = 0.07) 2
• This suggests no subclinical intestinal inflammation involving neutrophils in pediatric SIBO 2

Cystic Fibrosis Patients

In cystic fibrosis patients:

• Gastrointestinal inflammation (elevated fecal calprotectin) is common but doesn't correlate with SIBO status 3
• Calprotectin concentrations did not differ between SIBO-positive and SIBO-negative patients 3

Clinical Guidelines and Expert Opinion

The American Gastroenterological Association (AGA) clinical practice update on SIBO states:

• There is insufficient evidence to support the use of inflammatory markers such as fecal calprotectin to detect SIBO 4

Praxis Medical Insights notes that:

• Fecal calprotectin levels >150 μg/g are generally considered elevated 5
• Fecal calprotectin reliably differentiates IBD from IBS with specificity and sensitivity exceeding 85% 5
• However, these markers are not specific for any particular condition causing intestinal inflammation 5

Interpretation in Clinical Context

When evaluating elevated fecal inflammatory markers:

• Consider that these markers are non-specific indicators of intestinal inflammation 6
• They may be elevated in various organic conditions, not just SIBO 6
• Fecal calprotectin and lactoferrin primarily differentiate inflammatory from functional bowel disorders 6

Clinical Approach to Elevated Markers

If elevated fecal calprotectin or lactoferrin is found:

1. Do not assume SIBO is the only possible cause
2. Consider other inflammatory conditions, particularly IBD
3. For persistent symptoms (>14 days), evaluate for underlying etiologies including IBD and IBS 5
4. Consider endoscopy with biopsy, especially with moderate-to-severe symptoms or highly elevated markers 5

Caveats and Pitfalls

• Diagnostic specificity: Fecal inflammatory markers lack specificity for SIBO and may be elevated in many other conditions
• Population differences: The relationship between SIBO and these markers varies across different patient populations
• Monitoring limitations: While these markers may help monitor treatment response in established inflammatory conditions, their utility specifically for SIBO monitoring is limited
• False positives: In CF patients, sputum contamination can lead to false positive fecal calprotectin results 3

In conclusion, while SIBO may contribute to elevated fecal inflammatory markers in some patient populations (particularly those with predisposing conditions like systemic sclerosis), current evidence does not support using these markers as reliable diagnostic tools for SIBO across all patient groups.