Estimated Prevalence of Injection Drug Use in Spain

"Concerning the estimated number of injecting drug users, valid answers of 1551 named injecting users were obtained in the 2011 Household Survey on Alcohol and Drugs (EDADES), a total of 741 (48%)of whom had started treatment for drug abuse or dependence according to those surveyed, which, applied to the 3,549 injecting users (injection within the 12 months immediately prior to being admitted to treatment) who were admitted to treatment in Spain in 2010 led to an estimate of 7,393 (3,549/0.48) recent injecting drug users in 2010 who would not be in OMT [Opioid Maintenance Treatment]. To estimate the number of injecting users who were patients in OMT in 2010, it is assumed, as in previous years, that 40% of this population has used heroin within the last 12 months and that 17% thereof have been injecting drug users. Thus, the estimate would be of at least (81,022 patients in OMT in 2010 x 40% who have used heroin within the last 12 months = 32,408 and 32,408 x 17% injecting = 5,509).
"Hence, based on the treatment indicator data and on the estimated number of injecting users among those patients in OMT, estimates would be found of 12,902 (7,393 + 5,509) recent (within the last 12 months) injecting drug users, meaning a 8.1% decline in the estimated number of injecting drug users in comparison to the figures estimated for 2009, mainly at the expense of a decline in the number of injecting users admitted for treatment in 2010.
"One must bear in mind that, in the 2011 Spanish National Report, a review was conducted of the relative importance the injecting route has among those admitted to treatment for heroin use in general and among the group of those considered “older” (long-duration users older than 39 years of age) in particular, it was deemed appropriate to assume an injecting use among those undergoing OMT treatment similar to that which is found both among all of those admitted to treatment for heroin and among the “older” group, which was 17% in 2009 and remained unchanged in 2010. The percentage employed previously had been 40%, which is not in keeping with the decline in injecting use among heroin users recorded over the past few years.
"However, when, instead of using the number of injecting users admitted to treatment, the estimated number of injecting users who had undergone some treatment for drug abuse or dependence in 2009 was used (6,186 individuals, calculated based on the number of drug users for whom care was provided in 2010 = 93,732, multiplied by 6.6%, which is the percentage of those admitted for treatment – for any drug- in 2010 who had injected drugs within the last 12 months), an estimate was calculated of 12,888 (6,186/0.48 = 12,888). Lastly, on adding the estimated number of injecting users among those undergoing OMT, the figure of 18,397 (12,888 + 5,509) recent injecting users is calculated.
"Therefore, the estimated figure of recent injecting users (within the last 12 months) would fall within the range of 12,902 – 18,397 individuals."