Medicare Coverage of Routine Screening for Thyroid Dysfunction (2003) / Chapter Skim
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4. Screening for Thyroid Dysfunction
4. Screening for Thyroid Dysfunction
Pages 32-43
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From page 32... ...
We take advantage of the evidence review, which was conducted concurrently by Dr. Mark Helfand of the Oregon Health & Science University Evidence-based Practice Center for the Task Force; the review is contained in Appendix B of this volume.
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From page 33... ...
for early detection of cervical cancer; a blood cholesterol test to detect blood lipid abnormalities that may put someone at risk of heart attack, stroke, and other conditions; and mammography, which may detect early breast cancers that are more curable than when they become palpable to the patient or the professional. As a rule, society may tolerate less than perfect accuracy in a screening test and, if unavoidable, a higher level of adverse effects due to the screening test or its later clinical consequences than in primary prevention because of the high likelihood of emerging disease being present.
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From page 34... ...
Issues in Screening for Thyroid Dysfunction When considering screening for thyroid dysfunction, several issues concerning the application of the screening principles require discussion. First, as noted elsewhere in this volume, thyroid dysfunction is more than one condition.
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From page 35... ...
There is also the clinical situation in which a patient is tested for thyroid dysfunction because it is a known cause or aggravating factor for some other condition, such as atrial fibrillation or hyperlipidemia. For the purposes of this Committee's analysis anyone with recognized symptoms or a history of any kind of thyroid disease or exposure to an agent known to be thyrotoxic will not be considered a potential screening subject, and the search for thyroid dysfunction as a cause or complicating factor in patients with other conditions will not be considered a screening procedure.
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From page 36... ...
The distinction between biochemically defined "subclinical" or "overt" thyroid dysfunction in the screening population is less likely to be meaningful in terms of either burden of disease or potential to benefit from treatment. EVIDENCE OF EFFICACY OF SCREENING FOR THYROID DYSFUNCTION The Committee considered the evidence concerning the efficacy of biochemical screening for thyroid dysfunction using serum TSH levels in several ways: (1)
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From page 37... ...
, or prevention of progression to overt hypothyroidism, with any associated morbid consequences (Effect Cal. If the screening TSH level, however, is abnormally low and the free T4 is normal, then a designation of subclinical hyperthyroidism is made (Path D)
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From page 38... ...
Morbidity With respect to subclinical hyperthyroidism in persons not known to have thyroid disease, Helfand found one good-quality observational study showing that a low TSH level was associated with a substantially increased risk of atrial fibrillation. Although the clinical consequences of atrial fibrillation in such patients have not been studied longitudinally, this condition is generally associated with increased risk of stroke and other conditions and with a higher risk of death (Effect Did.
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From page 39... ...
Mortality With regard to the impact of subclinical hyperthyroidism on total mortality associated with subclinical hyperthyroidism, Helfand found one study where mortality was higher among those with low serum TSH levels. However, there was no adjustment for co-morbidity, which, as noted in Chapter 2, may cause low TSH levels in the absence of thyroid dysfunction and therefore create an association between low TSH levels and mortality that would be neither causal nor related to thyroid disease.
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From page 40... ...
Some patients found by screening to have overt hypothyroidism had symptoms of which the treating physicians were unaware, and in uncontrolled "pre/post" studies, reductions in high blood cholesterol levels were reported. Evidence of Efficacy of Treatment for Subclinical Hyperthyroidism Helfand found no controlled trials of the treatment for subclinical hyperthyroidism.
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From page 41... ...
These include nervousness, palpitations, atrial fibrillation, and exacerbation of angina pectoris. The randomized trials reviewed by Helfand did not systematically report adverse events, but some were reported incidentally and were of the types noted earlier.
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From page 42... ...
While treatment of subclinical hyperthyroidism effectively eliminates the biochemical condition, it usually leads to a hypothyroid state and to other adverse effects. Properly designed clinical studies are needed to determine whether treatment reduces the risks associated with hyperthyroidism, such as atrial fibrillation, and whether benefits outweigh adverse effects.
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From page 43... ...
United States Preventive Services Task Force.
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