Is faecal calprotectin a useful test in older adults?

William is a 58yr old man presenting with a 5-month history of change in bowel habit towards looser stool. 

He was going to come to the doctor a few months ago but coincidentally received his national bowel screening test though the post, which was negative. Reassured ‘nothing sinister was going on’ he decided that his symptoms were probably just part and parcel of getting a bit older, alongside the arthritis developing in his knees and elbows. However, recently he has started to wake with nocturnal diarrhoea. A few near accidents have proved the final straw, pushing him to overcome his embarrassment and come in to see the GP.

William reports no blood in the stool, no weight loss and no family history of bowel cancer. Interestingly, he thinks his mother suffered with colitis. Examination of his abdomen and DRE is unremarkable. You note mild swelling to his right knee.

So, what is causing Williams’ symptoms? Could this be a late presentation of IBD, with nocturnal defecation and a family history of colitis? Is faecal calprotectin (FC) likely to be a useful test in evaluating Williams’ symptoms?

FC is a marker of bowel inflammation, with BSG guidelines advocating use in those under the age of 40 to delineate possible inflammatory bowel disease from IBS. However, use in older adults is more complicated due to the higher likelihood of colorectal cancer and alternative organic pathology (e.g. diverticulitis).  The York Faecal Calprotectin Care Pathway suggests considering use between 16-60yrs when colorectal cancer is NOT suspected. NICE do not have a specific age cut off for FC use, but again only advocate usage where colorectal cancer is not suspected (HTG320). Those with risk factors for colorectal cancer should be assessed with FIT/ imaging as per NG12.  

So how does this apply to William? His change in bowel habit could be an early symptom of colorectal cancer, and he meets the NICE criteria for FIT (NG12).  Whilst he is reassured by his negative screening test, there is a clear indication to repeat the FIT using the lower threshold for symptomatic patients (10µg/g), alongside the usual bloods including a coeliac screen, and a stool sample for MC+S. Excluding colorectal cancer is the first priority.

What if FIT is negative? Is faecal calprotectin helpful for identifying older adults with IBD?

A new paper published in the BJGP examined the performance of FC in adults over aged 50yrs at identifying IBD. This was a UK based retrospective observational study looking at patients referred for colonoscopy who also had FC testing, totalling 669 patients (roughly 1/3 >50yrs, roughly 2/3 18-49yrs).

They found that FC >50 µg/g had a high sensitivity for IBD across both age cohorts (94.1% for those aged 18–49 years, 93.8% for those aged ≥50 years). Interestingly, FC >50 µg/g had a higher sensitivity for IBD than FIT (75% for those ≥50 years). 

The negative predictive value was also high at over 98% for both age groups, making it a helpful test for excluding IBD. 

However, specificity was low and the positive predictive value of FC was only 12.8% for those over 50 yrs (versus 20.9% in the younger cohort). Increasing the FC threshold to 150 µg/g only marginally increased PPV in older adults. 

The authors concluded that due to its high sensitivity for IBD ‘FC may have a role as a ‘rule-out’ test in adults aged ≥50 years who have lower GI symptoms and a negative FIT, when CRC is not suspected’. They also suggest that FC could be used to help stratify those who would benefit from further investigation. 

So, faecal calprotectin may be considered a useful test for William to assess for IBD in the context isolated loose stools, a negative FIT, and no other red flags for colorectal cancer. It could help triage the urgency of further investigation. If negative, the likelihood of IBD is low. However, keep in mind that it does not rule out microscopic colitis and onwards referral and colonoscopy may still be indicated if symptoms persist! Further, geographical access to FC for older adults is variable, with some labs operating strict age cuts off for testing. This may change with emerging evidence, but do check guidelines local for your area.