NEGATIVE FAECAL CALPROTECTIN RESULT USEFUL FOR RULING OUT IBD IN CHILDREN

Henderson P, Anderson NH, Wilson DC. The diagnostic accuracy of fecal calprotectin during the investigation of suspected pediatric inflammatory bowel disease: a systematic review and meta-analysis. Am J Gastroenterol 2014;109(5):637-645.

Abstract here

Not just children but adults as well. I’m sure there is unwritten law that when something interesting happens in medicine, when an article appears in the media or a patient brings in an Internet printout, like buses several articles appear at once. It happened to me recently with a patient who was diagnosed with Postural Tachycardia Syndrome (POTS) when an article appeared in the Telegraph stating that up to a third of fibromyalgia sufferers may have POTS (I was seeing my patient that day). It also happened with a PBSGL we did on infant feeding problems when other guidance came out and again it was in the media. So when this POEM arrived after I had recently attended the excellent Essential Knowledge Update course run by the Wessex Faculty of the RCGP, it was unsurprising to find the subject of faecal calprotectin being raised. This was on the background on recent local guidance for our practice and one of my GP partners attending an educational event.

This POEM is a summary of a meta-analysis looking at the use of the test in children when considering the diagnosis of Inflammatory Bowel Disease (IBD). The bottom line for me as a GP is to screen out the worried well & refer the suspected cases. I therefore need a test that correctly identifies those without disease – if I have a clinical concern, I will refer. The test measures the level of calprotectin and a cut off value is determined. Obviously the higher the cut off, the more accurate the test is at the cost of false negatives. The commonest cut off is 50ug per g of stool.

Whilst writing this I reviewed the NICE guidance which was produced in Oct 13. The results are remarkably convergent and I suspect the studies in both meta-analyses are similar (although I could not confirm this). The test has a high sensitivity – a patient with IBD is highly likely to have a positive test – with a sensitivity approaching 100% with a cut off of 50ug. The specificity varied, the greatest variation noted by NICE occurring in the paediatric group (44 to 93%) which was exactly the same as this study.

The likelihood ratios were quoted. The positive ratio was 3.1. This isn’t that high so it is saying that the test is moderately helpful as a test to identify IBD. This is because of it being raised in other conditions so whilst someone with IBD will have a positive test, if it is applied to a population, you will get IBD sufferers plus others. However the negative likelihood ratios was 0.03. This means the test is highly discriminatory in patients without IBD. If it is negative, it is very unlikely the patient has IBD.

In summary, in children the test is very useful for reassuring a patient does not have IBD but if it is positive, it doesn’t necessarily mean the child has IBD. Ultimately I would be guided by clinical presentation and parental ideas, concerns & expectations. One thing I have noticed about paediatricians is they are very helpful reviewing children of worried well parents. As a parent myself, that reassures me.

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