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Table 1 Characteristics of the studies meeting inclusion criteria

From: Which interactions matter in economic evaluations? A systematic review and simulation study

 Completed studiesProtocols and terminated studiesOverall
Publication yeara200918% (7/40)50% (7/14)26% (14/54)
200810% (4/40)14% (2/14)11% (6/54)
20075% (2/40)29% (4/14)11% (6/54)
200610% (4/40)0% (0/14)7% (4/54)
200515% (6/40)0% (0/14)11% (6/54)
2000–200428% (11/40)7% (1/14)6% (3/54)
Pre-200015% (6/40)0% (0/14)9% (5/54)
Mainly/entirely publicly funded75% (30/40)100% (14/14)81% (44/54)
Country where research doneUnited Kingdom28% (11/40)43% (6/14)31% (17/54)
United States38% (15/40)7% (1/14)30% (16/54)
Other individual country23% (9/40)29% (4/14)24% (13/54)
Multinational13% (5/40)21% (3/14)15% (8/54)
Disease areaCardiovascular disease45% (18/40)0% (0/14)33% (18/54)
Musculoskeletal13% (5/40)14% (2/14)13% (7/54)
Cancer15% (6/40)0% (0/40)11% (6/54)
Smoking, drugs or alcohol13% (5/40)29% (4/14)17% (9/54)
Other25% (10/40)57% (8/14)33% (18/54)
Factors target different diseases3% (1/40)14% (2/14)6% (3/54)
Type of interventionbPharmaceutical45% (18/40)36% (5/14)43% (23/54)
Physiotherapy, exercise and related15% (6/40)29% (4/14)19% (10/54)
Nutrition8% (3/40)14% (2/14)9% (5/54)
Surgery13% (5/40)7% (1/14)11% (6/54)
Training, counselling, incentives and logistical interventions50% (20/40)43% (6/14)48% (26/54)
Sample sizecMean (range)3420 (126, 20,536)1371 (132, 4733)3002 (126, 20,536)
< 200 patients13% (5/39)7% (1/14)11% (6/53)
200–999 patients38% (15/39)36% (5/14)38% (20/53)
> 1000 patients49% (19/39)29% (4/14)43% (23/53)
Type of economic evaluationCost-effectiveness analysis68% (27/40)0% (0/14)50% (27/54)
Cost-effectiveness and cost-utility analysis18% (7/40)43% (6/14)24% (13/54)
Cost-utility analysis8% (3/40)29% (4/14)13% (7/54)
Cost-consequence analysis8% (3/40)0% (0/14)6% (3/54)
Cost-utility and cost-benefit analysis0% (0/40)7% (1/14)2% (1/54)
Depends on results0% (0/40)7% (1/14)2% (1/54)
Not stated0% (0/40)14% (2/14)4% (2/54)
Cluster-randomised13% (5/40)43% (6/14)20% (11/54)
Type of designFull factorial88% (35/40)86% (12/14)87% (47/54)
Partial factorial10% (4/40)7% (1/14)9% (5/54)
Incomplete factorial3% (1/40)7% (1/14)4% (2/54)
Factorial matrix size2 factors & 2 levels2 (e.g. 2 × 2, 2 × 2 + 1, or double 2 × 2)78% (31/40)71% (10/14)76% (41/54)
> 2 factors each with 2 levels (e.g. 2x2x2)10% (4/40)0% (0/14)7% (4/54)
2 factors with > 2 levels on ≥1 factor (e.g. 3 × 2)10% (4/40)21% (3/14)13% (7/54)
> 2 factors with > 2 levels on ≥1 factor (e.g. 3x2x2)3% (1/40)7% (1/14)4% (2/54)
Primary clinical endpointAssumed no interaction53% (21/40)29% (4/14)46% (25/54)
Included interaction term23% (9/40)7% (1/14)19% (10/54)
Unclear25% (10/40)64% (9/14)35% (19/54)
Base case economic evaluationAssumed no interaction40% (16/40)7% (1/14)31% (17/54)
Included interaction term53% (21/40)0% (0/14)39% (21/54)
Unclear8% (3/40)93% (13/14)30% (16/54)
Presentation of uncertaintyNone48% (19/40)48% (19/40)
Present using confidence intervals and/or scatter graphs15% (6/40)15% (6/40)
Cost-effectiveness acceptability curvesPair-wise comparison(s)23% (9/40)23% (9/40)
Multiple comparison(s)8% (3/40)8% (3/40)
Pair-wise and multiple comparison(s)8% (3/40)8% (3/40)
  1. a Completed studies are categorised by the year when the first paper describing the results of the economic evaluation was published, while protocols are categorised by the date the protocol was published
  2. b Numbers add up to > 100% since 16 studies/protocols evaluated two or more different types of intervention
  3. c Excludes one cluster-randomised study for which the number of patients was not reported