title: Cancer incidence among patients with a hospital diagnosis of pruritus: a nationwide Danish cohort study.
abstract: BACKGROUND
  Pruritus is a frequent complaint in patients with cancer. However, no large study has examined pruritus as a marker of undiagnosed cancer.
  
  
  OBJECTIVE
  To examine the association between inpatient, outpatient and emergency hospital diagnoses of pruritus and subsequent cancer diagnoses.
  
  
  METHODS
  In this nationwide Danish cohort study, we used medical databases to identify all patients (n = 12,813) with a diagnosis of pruritus during the period 1978-2011 and followed them until a first-time cancer diagnosis, emigration, death or 31 December 2011. We computed standardized incidence ratios (SIRs) for cancer as the observed to expected number of cancers based on national cancer incidence rates. We calculated the 1-year absolute risk of cancer, treating death as a competing risk.
  
  
  RESULTS
  The overall SIR of cancer was 1.13 [95% confidence interval (CI) 1.07-1.20]: 1.22 (95% CI 1.13-1.33) among men and 1.05 (95% CI 0.97-1.14) among women. The SIR was 1.20 (95% CI 1.08-1.33) among patients with a previous diagnosis of dermatological disease and 1.10 (95% CI 1.02-1.18) among patients without such a diagnosis. Both haematological and various solid cancers were observed at increased rates. Overall, the highest SIRs were observed during the first 3 months of follow-up, declining rapidly thereafter. The 1-year absolute risk of a cancer diagnosis was 1.63% and 155 patients with pruritus would have needed to be examined to detect one excess cancer.
  
  
  CONCLUSIONS
  Pruritus may be a marker of occult cancer. Further studies are needed to assess the prognostic benefit of screening for cancer in patients with pruritus.
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, P.P. Ørumsgade 11, Aarhus C, 8000, Denmark.
authors.forename: S A
authors.initials: SA
authors.lastname: Johannesdottir
authors.forename: D K
authors.initials: DK
authors.lastname: Farkas
authors.forename: G R
authors.initials: GR
authors.lastname: Vinding
authors.forename: L
authors.initials: L
authors.lastname: Pedersen
authors.forename: A
authors.initials: A
authors.lastname: Lamberg
authors.forename: H T
authors.initials: HT
authors.lastname: Sørensen
authors.forename: A B
authors.initials: AB
authors.lastname: Olesen
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications* / Q000453:epidemiology; D011379:Prognosis; D011537:Pruritus / Q000150:complications* / Q000453:epidemiology; D055815:Young Adult