title: Poor validity of self-reported HBV vaccination among young heroin users in Spain supports the policy "don't ask, draw a blood sample, vaccinate and try to schedule another visit".
abstract: OBJECTIVE
  To assess the validity of self-reported hepatitis B virus vaccination status in young heroin users.
  
  
  METHODS
  Cross-sectional study among 949 street-recruited young injection heroin users (IHUs) and non-injection heroin users (NIHUs) in Madrid, Barcelona and Seville. Face-to-face interviews and dried blood spot tested for anti-HBc and anti-HBs. The validity of self-reported vaccination status was assessed comparing with the serological status. The percentage of agreement with the kappa (kappa) statistic and the positive predictive value were calculated.
  
  
  RESULTS
  The percentage of agreement between self-reported and serologic vaccination status was 51.9% overall, with little difference by city (53.1% in Barcelona, 49.0% in Madrid and 51.5% in Seville) or between IHUs (51.3%) and NIHUs (53.0%). All the kappa scores were lower than 0.1. The positive predictive value of self-reports was less than 25% in all categories analysed, except in the city of Barcelona (37%). Among those who indicated that they had been vaccinated, 31% were actually susceptible.
  
  
  CONCLUSIONS
  In areas with a high prevalence of infection and rising coverage of vaccination the policy "don't ask, take a blood sample, give a dose of vaccine and try to schedule another visit" should be recommended in clinical practice.
authors.affiliation: Centro Nacional de Epidemiología, Instituto de Salud Carlos III, Madrid, C/Sinesio Delgado 6, 28029 Madrid, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: de la Fuente
authors.forename: Carlos
authors.initials: C
authors.lastname: Toro
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Brugal
authors.forename: Fernando
authors.initials: F
authors.lastname: Vallejo
authors.forename: Vicente
authors.initials: V
authors.lastname: Soriano
authors.forename: Gregorio
authors.initials: G
authors.lastname: Barrio
authors.forename: Rosario
authors.initials: R
authors.lastname: Ballesta
authors.forename: María J
authors.initials: MJ
authors.lastname: Bravo
mesh_terms: D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D006291:Health Policy; D006508:Hepatitis Antibodies / Q000097:blood; D006509:Hepatitis B / Q000097:blood / Q000517:prevention & control*; D006512:Hepatitis B Core Antigens / Q000276:immunology; D006514:Hepatitis B Surface Antigens / Q000276:immunology; D003932:Heroin; D006801:Humans; D008297:Male; D013030:Spain; D015819:Substance Abuse, Intravenous; D011795:Surveys and Questionnaires; D014505:Urban Population; D014611:Vaccination; D014761:Viral Hepatitis Vaccines / Q000008:administration & dosage*
chemical_list: D006508:Hepatitis Antibodies; D006512:Hepatitis B Core Antigens; D006514:Hepatitis B Surface Antigens; D014761:Viral Hepatitis Vaccines; D003932:Heroin