We screened more than 3300 study abstracts and identified 533 original cost-utility analyses. Thirty nine studies were excluded because they did not report numerical incremental cost effectiveness ratios. In total, 1433 cost effectiveness ratios were reported in these 494 studies, with a median of 2.0 (interquartile range 1-3) and a range of 1-20 ratios per study. Overall, 130 incremental cost effectiveness ratios (9%) were reported as cost saving (they saved money and improved health simultaneously), 124 (9%) were dominated by their comparators (had worse health outcomes and increased costs), and 1179 (82%) increased costs but improved health outcomes.
Most studies were published in the 1990s (). The citation impact factor in the year before publication was available for 449 studies (91%). Cardiovascular and infectious disease interventions were the most commonly studied. Most studies were from the United States. About 18% were sponsored by industry, almost half were sponsored by non-industry sources, and sponsorship could not be determined in 34% of studies.
Characteristics of 494 cost-utility analyses of health interventions published between 1976 and 2001
shows the frequency distribution of all 1433 incremental cost effectiveness ratios. The median (interquartile range) ratio per QALY was $20 133 ($4520-74 400). Approximately half of the ratios (712; 50%) were below $20 000/QALY, two thirds (974; 68%) were below $50 000/QALY, and more than three quarters (1129; 79%) were below $100 000/QALY. When analysed according to study sponsorship, median (range) ratios per QALY were $13 083 ($3600-33 000) for those sponsored by industry and $27 400 ($4600-96 600) for those with non-industry sponsors. The median (range) cost effectiveness ratio per QALY for studies with unknown sponsorship was $18 900 ($4 960-64 300). Restricting the analysis to the lowest and highest ratios reported by each study yielded median ratios of $8784/QALY and $31 104/QALY ().
Frequency distribution of 1433 incremental cost effectiveness ratios for health interventions
Frequency distribution of lowest (brown) and highest (white) incremental cost effectiveness ratios in each study
Several study characteristics were associated with reporting incremental cost effectiveness ratios below one or all three thresholds (). The more quoted journals with a citation impact factor above 4 were less likely to publish ratios below $20 000/QALY (crude odds ratio 0.60, 95% confidence interval 0.42 to 0.86) or $50 000/QALY (crude 0.56, 0.38 to 0.82) than less quoted journals with a lower impact factor. However, this finding was not significant within the multivariable model ().
Characteristics of studies associated with favourable incremental cost effectiveness ratios according to three threshold values. Values are odds ratios (95% confidence intervals)
Studies funded by industry were more likely to report cost effectiveness ratios less than $20 000/QALY (adjusted odds ratio 2.1, 1.3 to 3.3), $50 000/QALY (3.2, 1.8 to 5.7), or $100 000/QALY (3.3, 1.6 to 6.8) than studies funded by non-industry sources (). Studies carried out in the US and Europe were significantly less likely to find favourable incremental cost effectiveness ratios than studies carried out elsewhere. Studies with quality scores for methodology above 5.5 were significantly less likely to report ratios below $20 000/QALY (0.48, 0.33 to 0.70) and $50 000/QALY (0.57, 0.39 to 0.83). Within the multivariable model, the association with quality remained significant only for cost effectiveness ratios below $20 000/QALY (adjusted odds ratio 0.58, 0.37 to 0.91; ).