Health state utilities in latent and active tuberculosis

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.

To characterize and compare utility scores from either active TB or latent TB infection (LTBI) participants.

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.

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.

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.