Use of fecal immunochemical testing in patients presenting in primary care with lower GI symptoms

I read with interest the CMAJ article “The appropriate use of fecal immunochemical testing”1 (FIT).

I agree with most of the points made and firmly support the view that there is no evidence that fecal occult blood testing (FOBT) and FIT are of any value in assessment of inpatients in secondary care,2^,3 particularly in acute admissions.4

However, I would argue strongly that the newer FIT (but not the traditional FOBT) are very useful in assessing the many patients who present in primary care with lower gastrointestinal symptoms.

Substantial evidence has accumulated over the last decade that a low fecal hemoglobin concentration is reassuring in symptomatic patients, as many studies show a very high negative predictive value for significant bowel disease (colorectal cancer, advanced adenoma and inflammatory bowel disease).5^,6 Moreover, a very high fecal hemoglobin concentration should lead to urgent referral. In Scotland, quantitative FIT is used and results reported as “not detected” if < 10 μg Hb/g feces, numerically if between 10 and 400 μgHb/g feces and > 400 μg Hb/g feces if above the upper measurement limit of the FIT system used.7 Fecal immunochemical testing has been widely introduced as a routine investigation available to general practitioners throughout the United Kingdom and is facilitating the referral for colonoscopy for those patients who would most benefit.

No diagnostic test is perfect, however, and a few cases of clinically important bowel disease will have a “negative” FIT result. The FIT result should not be interpreted in isolation, and relevant clinical indications for referral should be heeded. Further, for some patients with a negative FIT result, safety-netting strategies — in which people at low risk, but not no risk, of having cancer are actively monitored in primary care to see if the risk of cancer changes8 — may be required.9

Thus, although controversies remain,10 the use of FIT in assessment of patients with symptoms in primary care is considered well worth investigating in countries with limited colonoscopy capacity.