Iron-deficiency anaemia and delay in the diagnosis of colorectal cancer

Iron-deficiency anaemia (IDA) is a recognized complication of colorectal cancer (CRC) especially with right-sided tumours, and failure to investigate the anaemia in older patients may lead to a delay in diagnosis. The aims of this study were to establish the proportion of patients with CRC shown to have an IDA for more than six months before diagnosis and to establish the proportion of patients with IDA who subsequently prove to have CRC.

All patients presenting with confirmed CRC in a health district (catchment population 280000) in the 4 years 1996-9 were identified from the pathology database after ethical approval. The criteria for IDA were haemoglobin (Hb) < 10.1 g/dl plus mean corpuscular volume < 78 fl and/or mean corpuscular Hb concentration < 32 g/dl. The haematology data-base serving the same population was searched for evidence of: 1. IDA at diagnosis of CRC; 2. IDA more than 6 months and more than one year before the diagnosis of CRC; 3. The number of haematology referrals per annum in women over 55 and men over 50 years of age meeting the criteria for IDA.

Of 440 patients with colorectal cancer, 166 (38%) had IDA at diagnosis and of the latter 54 (12%) were known to have IDA for more than six months before diagnosis and 26 (6%) had IDA more than one year before diagnosis. IDA was more common in right sided tumours (65%) than in those arising in the left side of the colon and rectum (26%). The annual incidence of IDA in the sampled population was 1366 in the stated age group.

The investigation of iron-deficiency anaemia in older patients is important but in order to detect 26 patients with colorectal cancer a year earlier, the investigation of approximately 5000 patients would be required--a detection rate of less than 1%.