Clarification required: FOBT or not?

I appreciated the review by Del Giudice et al¹ on the topic of colorectal cancer (CRC) screening referral in the August issue of Canadian Family Physician. These guidelines, for the most part, are an excellent overview of a complex process. I write to simply ask for further clarification around the role of fecal occult blood testing (FOBT) as described by the authors.

Del Giudice et al¹ state that positive FOBT results require semiurgent referral, while negative FOBT results do not rule out CRC. Presumably, patients with negative FOBT results would then fall back into the wider pool, in which if their symptoms did not resolve within 4 to 6 weeks, they would also undergo semiurgent referral.

These guidelines seem to propose the following pathways for low-risk, symptomatic patients:

• semiurgent referral for a positive FOBT result (with a test presumably completed over 1 to 2 weeks);

• semiurgent referral for symptoms persisting longer than 4 weeks following a negative FOBT result, or in the absence of an FOBT; and

• no referral required if symptoms resolve in 4 weeks, irrespective of FOBT being done.

The key issue here is that regardless of whether the FOBT is done, a failure of symptoms to resolve in 4 weeks triggers a semiurgent referral and resolution does not. To me, the residual value of ordering an FOBT thus seems to be not to prevent referral, but rather to trigger a semiurgent referral slightly early (perhaps practicably possible 1 to 2 weeks earlier than waiting).

Given the increasing resource pressures on our health care system, there is a growing awareness of the need to avoid unnecessary testing (eg, the Choosing Wisely² campaign comes to mind). I wonder if Del Giudice and colleagues could comment on the evidence for improved outcomes and the health system resource burden provided by positive FOBT results triggering semiurgent referrals only slightly earlier, rather than a referral being triggered after 4 weeks of symptoms irrespective of whether the FOBT is ordered; and also explain what evidence led to the guidance that negative FOBT results do not rule out the need for a referral.

Taken together, to my mind, these 2 considerations seem to notably reduce the necessity and value of FOBT as an investigation in CRC screening and diagnosis, which in turn has considerable practice and health system implications.

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