title: Clinical features of bowel disease in patients aged <50 years in primary care: a large case-control study.
abstract: BACKGROUND
  Incidences of colorectal cancer (CRC) and inflammatory bowel disease (IBD) are increasing in those aged <50 years.
  
  
  OBJECTIVE
  To identify and quantify clinical features in primary care of CRC/IBD in those aged <50 years. This study considered the two conditions together and aimed to determine which younger patients, presenting in primary care with symptoms, would benefit from investigation for potentially serious colorectal disease.
  
  
  METHODS
  Matched case-control study using primary care records from the Clinical Practice Research Datalink, UK.
  
  
  METHODS
  Incident cases (aged <50 years) of CRC (n= 1661) and IBD (n= 9578) diagnosed between 2000 and 2013 were each matched with up to three controls (n= 3979 CRC;n= 22 947 IBD). 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 with CRC/IBD (allP<0.001): rectal bleeding, change in bowel habit, diarrhoea, raised inflammatory markers, thrombocytosis, abdominal pain, low mean cell volume (MCV), low haemoglobin, raised white cell count, and raised hepatic enzymes. 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.
  
  
  CONCLUSIONS
  This study quantified the risk of serious bowel disease in symptomatic patients aged <50 years in primary care. Rectal bleeding and change in bowel habit are strongly predictive of CRC/IBD when combined with abnormal haematology. The present findings help prioritise patients for colonoscopy where the diagnosis is not immediately apparent.
authors.affiliation: University of Exeter Medical School, Exeter.
authors.forename: Sally A
authors.initials: SA
authors.lastname: Stapley
authors.affiliation: School of Medicine, Pharmacy and Health, Durham University, Wolfson Research Institute, Stockton on Tees.
authors.forename: Greg P
authors.initials: GP
authors.lastname: Rubin
authors.affiliation: Bowel Cancer UK, London.
authors.forename: Deborah
authors.initials: D
authors.lastname: Alsina
authors.affiliation: University of Exeter Medical School, Exeter.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Shephard
authors.affiliation: University Hospital of North Tees, Stockton-on-Tees.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Rutter
authors.affiliation: University of Exeter Medical School, Exeter.
authors.forename: William T
authors.initials: WT
authors.lastname: Hamilton
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D015179:Colorectal Neoplasms / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012017:Referral and Consultation; D055815:Young Adult
keywords: colorectal neoplasms; diagnosis; general practice; inflammatory bowel diseases; signs and symptoms