Table 3. Costs of the SBI intervention, per person. Type of costs Approaching patients by GP-assistant Checking AUDIT score 8+, by GP Further screening by GP Brief intervention by GP Follow-up sessions by GP doi:10.1371/journal.pone.0005696.t003 Unit 1 min 1 min 5 min 10 min 20 min Unit price 0.66 2.19 2.19 2.19 2.19 Costs J0.66 J2.19 J10.95 J21.9 J43.8 been demonstrated. Wutzke et al. [23] concluded that there is no remaining effect after a period of 10 years when there are no regular check-ups. However, Nilssen [24] concluded that the impact of a brief intervention appears to be long lasting, up till 9 years after the provision of the intervention. In our study, we assumed that health effects only accrue if behavioural changes are maintained lifelong. The fraction of the Table 4. Summary of assumptions and input data. Assumptions Discount rate Time horizon Target population Distributions used in PSA Relative risks Fraction of the target population that agrees to be screened Sensitivity of the screening instrument Specificity of the screening instrument Fraction for second interview Decrease in alcohol consumption Fraction of decrease in alcohol consumption maintained aPooled estimate from all studies selected and described in Bertholet et al. [10]. A logistic random effects regression analyses with only a constant was carried to obtain the effect estimate and the uncertainty surrounding it. bPooled estimate from all studies selected and described in the systematic review by Fiellin et al. [12]. A logistic random effects regression analyses with only a constant was carried to obtain the effect estimate and the uncertainty surrounding it. cBertholet et al. [10]. doi:10.1371/journal.pone.0005696.t004 PLoS ONE | www.plosone.org 6 May 2009 | Volume 4 | Issue 5 | e5696 Excessive Alcohol Use initial decrease in alcohol consumption that is maintained in the long run was drawn from a uniform distribution with minimum 0 and maximum 1. Costs of the SBI intervention The costs of opportunistic screening and subsequent interven- tion were calculated by using a so-called bottom-up method as advocated in the Dutch Pharmacoeconomic guidelines [43]. All elements of the screening and intervention were identified and thereby the resources needed. These units and unit prices are displayed in Table 3. Altogether, the screening process costs about J14,- per person. Providing brief intervention costs about J22,- per person, and follow-ups costs are J44,- per person. Target population In this modelling study, the target population consisted of all people between age 20 and 65 who visit the GP in a particular year, which according to Statistics Netherlands (CBS), is approximately 7.2 million [6]. Current practice scenario SBI scenario 4% costs and 1.5% effects 80 years (lifetime) Risky drinkers aged between 20 and 65 who visit the GP yearly (50%) Lognormal distributions derived from meta analyses Holman [35] 4% costs and 1.5% effects 80 years (lifetime) Risky drinkers aged between 20 and 65 who visit the GP yearly (50%) Lognormal distributions derived from meta analyses Holman [35] Logit distribution (1/(1+e2x) with x normally distributeda: Mean: 1.802 SD: 0.237 Mean: 0.800 SD: 0.490 Mean: 2.763 SD: 0.168 Mean: 1.149 SD: 0.216 Mean: 1.149 SD: 0.216 Minimum: 0 Maximum: 1 Normal distributionc Uniform distribution Logit distribution (1/(1+e2x) with x normally distributedb: Logit distribution (1/(1+e2x) with x normally distributedb: Logit distribution (1/(1+e2x) with x normally distributeda: