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”

ObjectivesTo assess the validity of self-reported hepatitis B virus vaccination status in young heroin users.Study designCross-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 (κ) statistic and the positive predictive value were calculated.ResultsThe 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 κ 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.ConclusionsIn 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.