title: Contact sensitization to cobalt--multifactorial analysis of risk factors based on long-term data of the Information Network of Departments of Dermatology.
abstract: BACKGROUND
  Cobalt contact sensitization in consecutively tested patients is common. The sources of exposure, and thus clinical relevance, are mostly unclear.
  
  
  OBJECTIVE
  To examine (i) long-term time trends of sensitization, (ii) risk factors that may point to relevant exposures, and (iii) coupling with nickel sensitization.
  
  
  METHODS
  Data of all patients patch tested with cobalt(II) chloride hexahydrate (1% pet.) between 1992 and 2012 (n = 185 050) in the Information Network of Departments of Dermatology (IVDK, www.ivkd.org) were subjected to descriptive stratified and Poisson regression analysis.
  
  
  RESULTS
  The overall prevalence of positive patch test reactions was 5.23% (95% confidence interal 5.13-5.33%). Regarding time trends, there were significant increases for males aged 18-44 years and for females aged ≥45 years, and a significant variation of co-reactivity with nickel over time. Female sex almost doubled the risk of sensitization; age ≥45 years was associated with a 30% decrease in the risk of positive patch test reactions to cobalt, and atopic eczema with an approximately 20% increase.
  
  
  CONCLUSIONS
  Notwithstanding some diagnostic difficulties with the test preparation, a persistent, notable proportion of cobalt sensitization, isolated or coupled with nickel allergy, can be observed. This warrants further in-depth research into causative exposures, both at the workplace and in consumers.
authors.affiliation: Department of Medical Informatics, Biometry and Epidemiology, University of Erlangen/Nürnberg, D-91054, Erlangen, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Uter
authors.forename: Olaf
authors.initials: O
authors.lastname: Gefeller
authors.forename: Johannes
authors.initials: J
authors.lastname: Geier
authors.forename: Axel
authors.initials: A
authors.lastname: Schnuch
mesh_terms: D000293:Adolescent; D000328:Adult; D003035:Cobalt / Q000009:adverse effects*; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis* / Q000209:etiology*; D009783:Dermatitis, Occupational / Q000175:diagnosis / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009532:Nickel / Q000009:adverse effects; D010328:Patch Tests / Q000379:methods; D012044:Regression Analysis; D012307:Risk Factors; D013997:Time Factors; D055815:Young Adult
chemical_list: D003035:Cobalt; C029938:nickel sulfate; D009532:Nickel; C018021:cobaltous chloride
keywords: cobalt; contact sensitization; risk factors; time trend