Cost-effectiveness analysis of universal hypothyroidism screening in the general population aged 30-65 years in Spain

Hypothyroidism is an endocrine disorder that often begins in a subclinical form but can lead to non-specific symptoms and cardiovascular problems. Its prevalence is higher among women, and a significant proportion of cases remain undiagnosed. While previous studies assessed screening in specific populations (e.g. pregnant women, older adults), this study evaluates the cost-effectiveness of population-wide screening in adults aged 30-65 from the Spanish National Health System (NHS) perspective.

A cost-effectiveness Markov model was developed, simulating seven health states: subclinical hypothyroidism (undiagnosed and controlled), overt hypothyroidism (undiagnosed and controlled), euthyroid state, cardiovascular event, and death. Two strategies were compared: population-based screening versus no screening. Model inputs-transition probabilities, prevalence, costs, utilities, and screening effectiveness-were obtained from published literature. A panel of four clinical experts validated the model structure and assumptions. Lifetime costs and quality-adjusted life-years (QALYs) were estimated, and the incremental cost-effectiveness ratio (ICER) was calculated. Probabilistic, sensitivity, and scenario analyses were conducted.

Population-based screening for hypothyroidism in individuals aged 30-65 resulted in an incremental cost of €34.7 million and 6,037 QALYs gained over 35 years, yielding an ICER of €5,745/QALY, significantly below the Spanish willingness-to-pay threshold (€21,000/QALY). Screening also resulted in 33,215 additional diagnoses of subclinical hypothyroidism and 6,870 fewer cases of overt hypothyroidism. It was cost-effective in 99% of probabilistic simulations and under all tested screening intervals (1-5 years).

Key limitations include the use of constant transition probabilities and some inputs from international sources. Nonetheless, expert validation supports the model's relevance. The analysis adopts a conservative approach, excluding potential additional benefits like hyperthyroidism detection or integration with routine bloodwork, which could improve cost-effectiveness. Overall, hypothyroidism screening is a cost-effective strategy for the Spanish NHS, improving early detection, preventing progression, and enhancing quality of life in a frequently underdiagnosed population.