Clinical features of bowel disease in primary care: a large case-control study

Abstract

Background Colorectal cancer (CRC) and inflammatory bowel disease (IBD) incidences in the under-50s are increasing worldwide, including the UK. Aim To identify and quantify the clinical features in primary care of CRC/IBD in the under-50s.

Design and Setting Matched case-control study using anonymised electronic primary care records from the Clinical Practice Research Datalink, UK. Methods Incident cases (aged <50 years) of CRC (n=1,661) and IBD (n=9,578) diagnosed between 2000 and 2013 were each matched with ≤3 controls (n=3,979 CRC; n=22,947 IBD) on age, sex and general practice. Odds ratios (OR) and positive predictive values (PPV) were estimated for features of CRC/IBD in the year before diagnosis. Results Ten features were independently associated (OR, 95% confidence interval) with CRC/IBD (all p<0.001): rectal bleeding (42, 33-55), change in bowel habit (27, 19-39), diarrhoea (8.9, 7.5-11), raised inflammatory markers (5.4, 4.6-6.3), thrombocytosis (4.4, 3.4-5.7) abdominal pain (3.9, 3.4-4.5), low mean cell volume (MCV) (2.7, 2.1-3.5), low haemoglobin (2.5, 2.1-3.1), raised white cell count (1.5, 1.3-1.9), and raised hepatic enzymes (1.4, 1.2-1.6). PPVs were >3% for rectal bleeding with diarrhoea, thrombocytosis, low MCV, low haemoglobin or raised inflammatory markers; for change in bowel habit with low MCV, thrombocytosis or low haemoglobin; and for diarrhoea with thrombocytosis. Conclusion This study quantified the risk of serious bowel disease in symptomatic patients <50 in primary care. Rectal bleeding and change in bowel habit are strongly predictive of CRC/IBD when combined with abnormal haematology. Our findings help prioritise patients for colonoscopy where the diagnosis is not immediately apparent.