D’Souza and colleagues underestimate GPs’ clinical judgement in selecting patients for a faecal immunochemical test (FIT).1 NICE may recommend FIT for ‘low- risk’ symptomatic patients ‘without rectal bleeding who have unexplained (abdominal) symptoms but do not meet the criteria for a suspected cancer’,2 but this has not led to the ‘deluge’ of referrals or worsening of the ‘endoscopy capacity crisis’ in the centres where FIT has been adopted.3
The majority of the estimated 10% of consulting patients with abdominal complaints will not be referred for colonoscopy.1 GPs conduct a careful triage using history and examination, an understanding of their patients’ consulting patterns and comorbidity, preferences for testing, and by deciding when to respond to a positive result. Only a highly selected group of those tested and with a positive FIT are referred.
The NICE positive predictive value (PPV) threshold to rule in patients for urgent referral is 3%: the PPV for a low-risk symptom such as abdominal pain is 2% (increasing with age) compared with 5% for rectal bleeding.4 The PPV of a positive FIT in the low-risk symptomatic population is estimated at 13%.5 If FIT is positive, referral is uncontroversial; if negative, the PPV falls to <1%, making colonoscopy non-referral reasonable. FIT is more likely to result in a reduction of unnecessary (routine) endoscopy referrals for low-risk symptoms.
The UK’s routes to diagnosis data, cited by D’Souza, show us that a higher proportion of cancers are diagnosed at early stage when GPs investigate patients who do not meet 2WW criteria: those eligible for FIT. In order to achieve our nationwide target of 3 in 4 cancers diagnosed at an early stage by 2028,6 offering early investigation (and where necessary, referral) to the correct patients is crucial before more serious symptoms develop.
As a rule-in test for patients with low-risk symptoms, FIT enables the timely detection of cancer and other bowel disease in primary care. It may also play a role as a rule-out test for patients with high-risk symptoms, or in the future replace routine post-polypectomy colonoscopy surveillance. Introducing FIT may have been the most important change in the whole of NG12.4
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