Health State Utilities in Latent and Active Tuberculosis

Background: Tuberculosis (TB) remains a major public health threat worldwide. Numerous cost-effectiveness analyses of TB screening and treatment strategies have been recently published, but none have utilized quality-adjusted life-years as recommended because of the lack of utilities for TB health states. Objective: To characterize and compare utility scores from either active TB or latent TB infection (LTBI) participants. Methods: Consenting patients attending a population-based screening and treatment clinic were administered the Short Form 36 (SF-36), the Health Utilities Index 2/3 (HUI2/3), and a general health visual analog scale (VAS) along with demographic questions. SF-36 scores were converted to Short Form 6D (SF-6D) utility scores using an accepted algorithm. Utility results were compared across scales, and construct validity was assessed. Results: A total of 162 TB patients (78 LTBI and 84 active TB) with available SF-36 and all four utility scores (Health Utilities Index 2, Health Utilities Index 3, SF-6D and VAS) were included in the analysis. Those with active TB had significantly lower SF-36 and utility scores than those with LTBI. Although all appeared to exhibit construct validity, the HUI2/3 and the VAS appeared to have significant ceiling effects, whereas the SF-6D had significant floor effects. Conclusions: Health state utility values for active TB and LTBI have been determined using different instruments. The three measures did not generate identical utility scores. The HUI2/3 was limited by ceiling effects, whereas the SF-6D appeared to display floor effects.