OBJECTIVES: To investigate the relationship between time horizon, Qalys, and Incremental Cost-Effectiveness Ratio (ICER) in the Health Technology Assessment (HTA) opinions of the French National Authority for Health (HAS).

METHODS: HTA opinions issued by the economic committee of HAS from 2014 to May 2024 were extracted from the HAS website, encompassing both drugs and medical devices. Products with available data on the time horizon and results (ICER and QALYs) were included in the analysis.

RESULTS: Out of 221 opinions currently available, 164 (75%) provided sufficient data for analysis and were not considered outliers. Among these, 52 opinions (31%) employed a "lifetime" time horizon, while 115 (69%) used a restricted time horizon. There was no statistically significant difference in ICER values between the two groups (p-value: 0.081).

A significant correlation was found between time horizon and the difference in QALYs, with a Pearson correlation coefficient of 0.546 (p-value: 2.23×10⁻¹⁴). This suggests that a longer time horizon is associated with a larger difference in QALYs, which may lead to misinterpretation of results.

Adjusting the difference in QALYs by the time horizon corrects this bias and facilitates comparison between opinions. As anticipated, the correlation after adjustment was non-significant (-0.024, p-value: 0.771).

CONCLUSIONS: Health economic evaluation results, such as ICER and QALYs, are influenced by various assumptions and driving parameters. The time horizon is a crucial factor that can lead to misinterpretations, particularly when comparing QALY results across different opinions. Adjusting QALYs by the time horizon can mitigate these discrepancies. These findings underscore the importance of considering the time horizon in HTA evaluations to ensure accurate and comparable results.