The importance of anaemia in diagnosing colorectal cancer: a case–control study using electronic primary care records

Although anaemia is recognised as a feature of colorectal cancer, the precise risk is unknown. We performed a case-control study using electronic primary care records from the Health Improvement Network database, UK. A total of 6442 patients had a diagnosis of colorectal cancer, and were matched to 45 066 controls on age, sex, and practice. We calculated likelihood ratios and positive predictive values for colorectal cancer in both sexes across 1 g dl(-1) haemoglobin and 10-year age bands, and examined the features of iron deficiency. In men, 178 (5.2%) of 3421 cases and 47 (0.2%) of 23,928 controls had a haemoglobin