Table 2.

Characteristics of included studies

	1990–1998 (n = 87)		1999–2004 (n = 196)		1990–2004 (n = 283)
	No. (%) studies		No. (%) studies		No. (%) studies
By study type
Cost minimization	16	(18.4)	23	(11.7)	39	(13.8)
Cost consequence	13	(14.9)	34	(17.4)	47	(16.6)
Cost effectiveness (life years gained)	17	(19.5)	35	(17.9)	52	(18.4)
Cost effectiveness (clinical outcome)	38	(43.7)	88	(44.9)	126	(44.5)
Cost utility	3	(3.5)	15	(7.7)	18	(6.4)
Cost benefit	0	(0)	1	(0.5)	1	(0.4)
By study design
Alongside RCT	3	(3.5)	31	(15.8)	34	(12.0)
Modeling study	53	(60.9)	101	(51.5)	154	(54.4)
Combination RCT/Modeling	3	(3.5)	15	(7.7)	18	(6.4)
Observational	28	(32.2)	49	(25.0)	77	(27.2)
By study perspective (as stated by authors)
Not stated	51	(58.6)	75	(38.3)	126	(44.5)
Third party payer (e.g., insurance)	32	(36.8)	83	(42.4)	115	(40.6)
Societal	4	(4.6)	24	(12.2)	28	(9.9)
Other (mainly 'patients')*	0	(0)	14	(7.1)	14	(5.0)
By disease category (ICD-9 category heading)
Circulatory system	22	(25.3)	35	(17.9)	57	(20.1)
Neoplasms	13	(14.9)	23	(11.7)	36	(12.7)
Infectious and parasitic	12	(13.8)	20	(10.2)	32	(11.3)
Nervous system and sense organs	4	(4.6)	20	(10.2)	24	(8.5)
Endocrine, nutritional, metabolic	7	(8.1)	15	(7.7)	22	(7.8)
Other*	29	(33.3)	83	(42.3)	112	(39.6)
By level of care
Curative	63	(72.4)	148	(75.5)	211	(74.6)
Rehabilitative	2	(2.3)	6	(3.1)	8	(2.8)
Preventive	22	(25.3)	42	(21.4)	64	(22.6)
By intervention type
Pharmaceutical	49	(56.3)	96	(49.0)	145	(51.2)
Medical procedure	6	(6.9)	38	(19.4)	44	(15.6)
Screening	12	(13.8)	16	(8.2)	28	(9.9)
Other*	20	(23.0)	46	(23.5)	66	(23.3)

* Summarized over extracted categories