DON’T repeat a positive test. I understand why we might be tempted to. After all, we routinely re-order tests that are a little out of range. And we repeat Pap tests which have mild abnormalities. But the FOBT’s sensitivity is as low as 50 per cent. Remembering back to my medical school epidemiology days, Sensitivity Rules Things Out (Remember SPin and SNout anyone?) Thus, high sensitivity helps us avoid false negatives. With a sensitivity of 50 per cent, a follow-up negative test has a 50 per cent chance of being a false negative.
DO go straight to colonoscopy in a patient with symptoms, and forgo the FOBT.
DON’T use the FOBT within 10 years of a colonoscopy.
DO send your patient for another scope if you happen to mistakenly do the FOBT within 10 years of the scope, and it’s positive. The further away the scope was, the higher their risk of cancer.
DON’T ignore even one window that’s positive. There are two windows on the test and they report results from three dates. That’s six windows. If any ONE of these is positive, the patient needs a scope.
DON’T defer a colonoscopy if the FOBT is positive even if the patient has rectal bleeding, known hemorrhoids, eaten beets, drank red wine, etc.
DO be timely. Patients with a positive FOBT should get scoped within 8 weeks! It should be considered an urgent referral.
DO consider the FOBT to be a long-term commitment. This test’s value comes from the repetition over years. Colorectal polyps usually grow slowly and if caught can be removed to prevent cancer.
DON’T forget to push a little more firmly with men, who typically have lower screening rates than women.
DON’T wait for the new FIT test. It’s coming but we don’t know exactly when, so please offer the FOBT. I will blog more about the new FIT test for colorectal cancer screening, likely in 2017 when ColonCancerCheck plans to launch it.