Researchers studied 445 people with irritable bowel syndrome (IBS) to see if simple blood and stool tests could predict who would feel better with treatment. They measured inflammation markers before and after 8 weeks of either a special diet or medication. While both treatments reduced some inflammation markers, these tests didn’t help predict which patients would improve or how much relief they’d get. This suggests doctors can’t rely on these simple tests alone to guide IBS treatment decisions, and that IBS may involve more complex factors than just inflammation.

The Quick Take

  • What they studied: Can simple blood and stool tests that measure inflammation help doctors predict which IBS patients will feel better with treatment?
  • Who participated: 445 adults with IBS from primary care clinics who were randomly assigned to either follow a special low-FODMAP diet or take a medication called otilonium bromide for 8 weeks.
  • Key finding: The inflammation markers tested (including calprotectin, defensin, and C-reactive protein) did not match up with how severe patients’ symptoms were, and they couldn’t predict who would improve with either treatment. However, both treatments did reduce some inflammation markers after 8 weeks.
  • What it means for you: If you have IBS, your doctor probably shouldn’t rely on these inflammation tests alone to decide your treatment plan. IBS appears to be more complicated than just inflammation, so treatment decisions should consider your individual symptoms and response rather than test results.

The Research Details

This was a sub-analysis of a larger study called DOMINO, which randomly assigned IBS patients to receive either a low-FODMAP diet (a special eating plan that limits certain carbohydrates) or medication. Researchers collected blood and stool samples from 445 patients before treatment started and again after 8 weeks. They measured five different inflammation markers in these samples and compared the results to how severe each patient’s symptoms were using a standard symptom severity scale.

The researchers used statistical tests to look for connections between the inflammation markers and symptom severity, and to see if the markers could predict who would improve with treatment. They also tracked how the inflammation markers changed after the 8-week treatment period for both groups.

Understanding whether simple tests can predict IBS treatment success is important because it could help doctors personalize treatment plans. If these markers worked, doctors could use them to quickly identify which patients would benefit from diet changes versus medication. However, the study shows that IBS is more complex than these markers suggest, meaning doctors need to consider the whole picture of each patient’s symptoms.

This study has several strengths: it included a large number of patients (445), used a randomized design that’s considered reliable, and measured multiple inflammation markers to get a complete picture. The study was conducted in real primary care settings, making results more applicable to everyday medical practice. However, the study only followed patients for 8 weeks, so we don’t know if results would be different over longer periods. Additionally, only a small percentage of patients had abnormal inflammation marker levels at the start, which may have made it harder to see connections.

What the Results Show

At the beginning of the study, most patients had normal inflammation marker levels. Only 2-20% of patients showed abnormal results on any single test, with C-reactive protein being abnormal in just 2% of patients. Importantly, the inflammation markers didn’t match up with how severe patients’ symptoms were—patients with high inflammation markers weren’t necessarily the ones with the worst symptoms, and vice versa.

After 8 weeks of treatment, both groups showed some reduction in inflammation. The low-FODMAP diet group showed significant decreases in two markers: beta-defensin-2 and fecal calprotectin. The medication group showed a significant decrease in beta-defensin-2 only. This suggests both treatments have some anti-inflammatory effect, even though the inflammation markers didn’t predict who would improve.

One interesting finding was that patients with constipation-predominant IBS had lower C-reactive protein levels compared to other IBS subtypes, suggesting different IBS types may involve different inflammatory patterns. However, this difference didn’t help predict treatment response.

The study found that inflammation markers decreased after treatment in both groups, suggesting that both the diet and medication approaches have some effect on reducing inflammation in the gut. However, these reductions in inflammation didn’t necessarily match up with symptom improvement, indicating that inflammation reduction alone doesn’t explain why patients feel better. This suggests that IBS symptom relief may involve multiple mechanisms beyond just reducing inflammation.

Previous research has suggested that inflammation might play a role in IBS, but this large study provides strong evidence that simple inflammation markers aren’t reliable predictors of treatment success. The findings align with growing understanding that IBS is a complex condition involving the gut-brain connection, not just inflammation. This study adds important evidence that doctors shouldn’t rely solely on inflammation tests when deciding IBS treatment.

The study only followed patients for 8 weeks, so we don’t know if the patterns would continue longer. Most patients had normal inflammation marker levels at the start, which made it harder to see if abnormal levels would predict outcomes. The study didn’t measure all possible inflammation markers, so other unmeasured markers might be more predictive. Additionally, the study focused on primary care patients, so results might differ in specialty care settings. The study also didn’t deeply explore why inflammation decreased without matching symptom improvement, leaving questions about the mechanisms involved.

The Bottom Line

If you have IBS, work with your doctor to find the right treatment based on your specific symptoms and how you respond, rather than relying on inflammation test results alone. A low-FODMAP diet appears effective for many people and may be worth trying under professional guidance. Standard IBS medications may also help. Consider keeping a symptom diary to track what works for you personally. Confidence level: Moderate—this is based on a large, well-designed study, but more research is needed to fully understand IBS mechanisms.

This research matters most for people with IBS who are trying to decide between diet changes and medication, and for their doctors making treatment recommendations. It’s particularly relevant for primary care doctors who see many IBS patients. People with other digestive conditions should not assume these findings apply to them. If you have severe or worsening symptoms, consult your healthcare provider regardless of test results.

Both treatments showed some changes in inflammation markers within 8 weeks, but symptom improvement may vary. Some people notice relief within days or weeks of starting a low-FODMAP diet, while others take several weeks to see benefits. Medication effects also vary by individual. Give any treatment at least 4-8 weeks before deciding if it’s working for you, and track your symptoms carefully during this period.

Want to Apply This Research?

  • Log your IBS symptoms daily using a simple 1-10 severity scale, noting specific symptoms (bloating, pain, bowel changes) and what you ate. This personal tracking is more useful than inflammation tests for predicting what works for you.
  • If trying a low-FODMAP diet, use the app to track which foods trigger your symptoms and which ones you tolerate well. Create a personalized food list based on your actual response rather than general guidelines, since inflammation markers don’t predict individual responses.
  • Set up weekly symptom summaries to identify patterns over 4-8 week periods. Compare your symptom trends to treatment changes (diet modifications or medication adjustments) to see what actually improves your symptoms. This individual tracking approach is more valuable than relying on inflammation test results.

This research summary is for educational purposes and should not replace professional medical advice. IBS diagnosis and treatment should always be managed by a qualified healthcare provider. The findings suggest inflammation tests alone shouldn’t guide treatment decisions, but your doctor may still recommend these tests as part of comprehensive care. If you have IBS symptoms, consult your healthcare provider before making significant dietary changes or starting new medications. This study involved adults in primary care settings; results may not apply to all populations or severity levels of IBS.