Predictive values of colorectal cancer alarm symptoms in the general population: a nationwide cohort study

Background: Alarm symptoms are used in many cancer referral guidelines. The objectives were to determine the 1-year predictive values (PVs) of colorectal cancer (CRC) alarm symptoms in the general population and to describe the proportion of alarm symptoms reported prior to diagnosis. Methods: A nationwide prospective cohort of 69,060 individuals ≥40 years randomly selected from the Danish population was invited to complete a survey regarding symptoms and healthcare-seeking in 2012. Information on CRC diagnoses in a 12-month follow-up came from the Danish Cancer Registry. PVs and positive and negative likelihood ratios were calculated. Results: A total of 37,455 individuals participated (response rate 54.2%). Sixty-four individuals were diagnosed with CRC. The single symptom with the highest positive PVs (PPV) and LR+ was rectal bleeding. PPVs were generally higher among individuals aged ≥75 years and highest among those reporting at least one specific alarm symptom that led to a GP contact. Conclusion: In general, the PPVs of CRC alarm symptoms are low and the NPVs high, especially in the youngest age groups. The LR + show a relative association with specific symptoms like rectal bleeding. Future campaigns on early diagnosis of CRC should focus on healthcare-seeking when experiencing rectal bleeding and target older people with the highest incidence.