METHODS: We developed a state-transition Markov model to compare the incremental cost per quality-adjusted life-year (QALY) gained between two different screening strategies and the strategy of no screening. Our screening strategies consist of a one-time screen in the first trimester of pregnancy using either anti-thyroid peroxidase (anti-TPO) antibodies or thyroid-stimulating hormone (TSH), followed by further testing if the screen is positive and subsequent treatment of women with hypothyroidism. The model accounts for medical consequences of autoimmune thyroid disease and hypothyroidism such as gestational hypertension, postpartum thyroiditis, and potential low IQ in the infants of untreated hypothyroid mothers. We performed a lifetime analysis taking a societal perspective. Using available literature and expert judgment we made base-case assumptions on the age at pregnancy (25 years), disease prevalence (10.4% for anti-TPO antibody positivity, 2.2% for TSH elevation), sensitivity and specificity of the anti-TPO test (90% and 95% respectively), cost of screening ($20 for anti-TPO and $23 for TSH screening), annual levothyroxine medication cost ($131) and other variables. We varied all assumptions widely in sensitivity analyses.
RESULTS: In the base-case analysis, TSH screening dominated the strategy of no screening. Screening using anti-TPO antibodies was cost-effective compared with screening using TSH, at $15,958 per QALY. This compares favorably to the cost-effectiveness of other well accepted screening practices. In sensitivity analyses, screening with anti-TPO antibodies remained cost-effective compared with TSH screening, while the latter continued to dominate the no screening strategy across a wide range of ages at screening, costs of screening, costs of treatment, and probabilities of adverse outcomes. The results were most influenced by the probability of diagnosing hypothyroidism in unscreened subjects or subjects with a normal screening test and by the probability that TSH is elevated in anti-TPO antibody negative subjects.
CONCLUSIONS: Screening pregnant women for autoimmune thyroid disease using TSH is cost-saving compared with no screening, while screening using anti-TPO antibodies is economically favorable compared with TSH screening. The medical community should strongly consider screening pregnant women with anti-TPO antibodies in the first trimester.