The cost-effectiveness of three thyroid function testing strategies for suspicion of hypothyroidism in a primary care-setting.
OBJECTIVE
To determine the sensitivity and specificity of thyroxine (T4) and the cost-effectiveness of three testing strategies in the diagnosis of hypothyroidism in a primary care setting.


METHODS
1) A retrospective chart review to determine sensitivity and specificity of T4 in diagnosing hypothyroidism; a cost-effectiveness analysis comparing ordering an initial T4 test alone, an initial thyroid-stimulating hormone (TSH) test alone, and T4 and TSH tests together in diagnosing hypothyroidism; a sensitivity analysis was performed on critical assumptions.


METHODS
Primary care adult practice of a health maintenance organization.


METHODS
Eight hundred sixteen consecutive patients suspected of having hypothyroidism who had both T4 and TSH tests performed.


METHODS
None.


RESULTS
The sensitivity of a T4 cut-off of 7 micrograms/dl (90.3 nmol/L) in diagnosing primary hypothyroidism was 93% (95% confidence interval = 85-100%) and the specificity was 68% (95% confidence interval = 65-71%). The cost-effectiveness ratios of using an initial T4 or TSH test were about the same across a wide range of test characteristics and disease prevalence estimates. As the ratio of T4 to TSH test charges declines from 0.6 to 0.2, the marginal cost of the TSH-first method increases from $3,500 to $18,000 for each additional hypothyroid patient identified. Ordering both tests together was very costly compared with the single test methods ($125,000 for each additional case diagnosed) and remained so under a wide range of assumptions.


CONCLUSIONS
When hypothyroidism is suspected, a TSH-first testing approach is generally preferable due to its greater sensitivity and, under most assumptions, only small increment in average or marginal cost per case compared with a T4-first method.
Schectman
J M
JM
Department of Health Care Sciences, George Washington University Medical Center, Washington, DC 20037.
Pawlson
L G
LG
D003362:Cost-Benefit Analysis; D006801:Humans; D007037:Hypothyroidism / Q000175:diagnosis*; D011320:Primary Health Care / Q000191:economics*; D012372:ROC Curve; D013960:Thyroid Function Tests / Q000191:economics*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood
D013972:Thyrotropin; D013974:Thyroxine