Supplementary Digital Content 1. Example of search strategy and results returned (date of search 01/03/2013)

# / Terms entered / Search carried out / PubMed
1 / health service / health services[MeSH Terms] OR ("health"[All Fields] AND "services"[All Fields]) OR "health services"[All Fields] OR ("health"[All Fields] AND "service"[All Fields]) OR "health service"[All Fields] / 1681245
2 / healthcare OR health care / ("delivery of health care"[MeSH Terms] OR ("delivery"[All Fields] AND "health"[All Fields] AND "care"[All Fields]) OR "delivery of health care"[All Fields] OR "healthcare"[All Fields]) OR ("delivery of health care"[MeSH Terms] OR ("delivery"[All Fields] AND "health"[All Fields] AND "care"[All Fields]) OR "delivery of health care"[All Fields] OR ("health"[All Fields] AND "care"[All Fields]) OR "health care"[All Fields]) / 1231106
3 / ambulatory care / ambulatory care[MeSH Terms] OR ("ambulatory"[All Fields] AND "care"[All Fields]) OR "ambulatory care"[All Fields] / 70443
4 / hospital / hospitals[MeSH Terms] OR "hospitals"[All Fields] OR "hospital"[All Fields] / 2649336
5 / outpatient OR out-patient / ("outpatients"[MeSH Terms] OR "outpatients"[All Fields] OR "outpatient"[All Fields]) OR ("outpatients"[MeSH Terms] OR "outpatients"[All Fields] OR ("out"[All Fields] AND "patient"[All Fields]) OR "out patient"[All Fields]) / 219819
6 / 1 OR 2 OR 3 OR 4 OR 5 / 4431632
7 / utilisation OR utilization / utilisation[All Fields] OR ("utilization"[Subheading] OR "utilization"[All Fields]) / 247645
8 / Cost / economics[Subheading] OR "economics"[All Fields] OR "cost"[All Fields] OR "costs and cost analysis"[MeSH Terms] OR ("costs"[All Fields] AND "cost"[All Fields] AND "analysis"[All Fields]) OR "costs and cost analysis"[All Fields] / 540569
9 / Expenditure / health expenditures[MeSH Terms] OR ("health"[All Fields] AND "expenditures"[All Fields]) OR "health expenditures"[All Fields] OR "expenditure"[All Fields] / 42637
10 / 7 OR 8 OR 9 / 765770
11 / Human immunodeficiency virus OR HIV OR AIDS / (("hiv"[MeSH Terms] OR "hiv"[All Fields] OR ("human"[All Fields] AND "immunodeficiency"[All Fields] AND "virus"[All Fields]) OR "human immunodeficiency virus"[All Fields]) OR ("hiv"[MeSH Terms] OR "hiv"[All Fields])) OR ("acquired immunodeficiency syndrome"[MeSH Terms] OR ("acquired"[All Fields] AND "immunodeficiency"[All Fields] AND "syndrome"[All Fields]) OR "acquired immunodeficiency syndrome"[All Fields] OR "aids"[All Fields]) / 342385
12 / Patient characteristics / ("patients"[MeSH Terms] OR "patients"[All Fields] OR "patient"[All Fields]) AND characteristics[All Fields] / 215275
13 / Determinants / determinants[All Fields] / 98474
14 / Predictors / predictors[All Fields] / 112007
15 / 12 OR 13 OR 14 / 408350
16 / 6 AND 10 AND 11 AND 15 / 1299