Putting Prevention into Practice
An Evidence-Based Approach
Screening for Thyroid Disease
Am Fam Physician. 2005 Apr 1;71(7):1369-1370.
LF, a 50-year-old woman, requests a “thyroid blood test.” You review the symptoms of hypothyroidism and hyperthyroidism with her and find that she has none of them. She still is concerned because “a doctor on television said all women should have this test.”
Case Study Questions
Based on recommendations from the U.S. Preventive Services Task Force (USPSTF), which one of the following statements should be considered in LF’s care?
A. Physicians should screen all adults for thyroid disease.
B. Physicians should not screen adults for thyroid disease.
C. Evidence is insufficient to recommend for or against routine screening for thyroid disease in adults.
D. Physicians should screen high-risk adults for thyroid disease.
E. Physicians should screen adults older than 50 years for thyroid disease.
Which one of the following statements about thyroid screening and treatment in screen-detected patients is correct?
A. The thyroid-stimulating hormone (TSH) test can detect subclinical thyroid disease.
B. Treatment of subclinical thyroid disease improves clinically important outcomes in adults with screening-detected disease.
C. When TSH is used for screening primary care populations, a positive screening test result almost always leads to a diagnosis of thyroid disease.
D. Subclinical hyperthyroidism is more common than subclinical hypothyroidism.
E. False-positive tests are less common in elderly patients.
Which of the following statements about adults with subclinical thyroid disease are correct?
A. Subclinical hyperthyroidism is associated with atrial fibrillation, dementia, and osteoporosis.
B. Subclinical hypothyroidism is associated with poor obstetric outcomes and poor cognitive development in children.
C. There is clear evidence that adults with subclinical hypothyroidism have a decreased quality of life.
D. Progression from subclinical to clinical disease in patients without a history of thyroid disease is not clearly established.
The correct answer is C. The USPSTF concluded that the evidence is insufficient to recommend for or against routine screening for thyroid disease in asymptomatic adults. The USPSTF found no controlled studies that examined whether routine screening for thyroid disease in the primary care setting leads to improved symptoms or other health outcomes. Although the yield of screening is greater in certain high-risk groups (e.g., postpartum women, persons with Down syndrome, elderly persons), the USPSTF found poor evidence that screening these groups leads to clinically important benefits. False-positive test results have the potential for harm, although the magnitude of harm is not known. There is good evidence of overtreatment with levothyroxine in many patients, but the long-term harmful effects of overtreatment are not known. As a result, the USPSTF could not determine the balance of benefits and harms of screening asymptomatic adults for thyroid disease.
The correct answer is A. Subclinical thyroid dysfunction is an abnormal biochemical measurement of thyroid hormones in patients without specific clinical signs or symptoms of thyroid disease and with no history of thyroid dysfunction or therapy. This includes patients with mildly elevated TSH and normal thyroxine (T4) and triiodothyronine (T3) levels (i.e., subclinical hypothyroidism) or low TSH and normal T4 and T3 levels (i.e., subclinical hyperthyroidism). Subclinical thyroid disease is much more common than overt disease in primary care populations. Up to 5 percent of women and 3 percent of men have subclinical hypothyroidism. Subclinical hyperthyroidism occurs in 1 percent of men older than 60 and 1.5 percent of women older than 60.
Screening for thyroid dysfunction can be conducted using the medical history, physical examination, or any of several serum thyroid function tests. The TSH test can detect subclinical thyroid disease. However, when TSH is used for screening primary care populations, the probability that an abnormal result represents true disease (i.e., positive predictive value) is lower. Furthermore, interpretation of a positive test result often is complicated in certain populations. For example, false-positive results are more common in elderly patients and in those with a severe underlying illness.
The correct answers are A, B, and D. Subclinical hyperthyroidism has been associated with atrial fibrillation, dementia, and, less clearly, osteoporosis. Subclinical hypothyroidism is associated with poor obstetric outcomes and poor cognitive development in children. Evidence for dyslipidemia, atherosclerosis, and decreased quality of life in adults with subclinical hypothyroidism in the general population is inconsistent and less convincing. Progression from subclinical to clinical disease in patients without a history of thyroid disease is not clearly established.
Helfand M. Screening for subclinical thyroid dysfunction in nonpregnant adults: a summary of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med. 2004;140:128–41.
Helfand M. Screening for thyroid disease. Systematic evidence review no. 23. Prepared by the Oregon Health and Science University Evidence-based Practice Center under contract no. 290–97–0018. Rockville, Md.: Agency for Healthcare Research and Quality, 2004. Accessed online January 31, 2005, at:http://www.ahrq.gov/clinic/prev/thyrdinv.htm.
U.S. Preventive Services Task Force. Screening for thyroid disease: recommendation statement. Ann Intern Med. 2004;140:125–7.
The case study and answers to the following questions on screening for thyroid disease are based on the recommendations of the U.S. Preventive Services Task Force (USPSTF), part of the Put Prevention into Practice program of the Agency for Healthcare Research and Quality (AHRQ). This recommendation was released in 2004. More detailed information on this subject is available in the USPSTF Recommendations and Rationale, the summary of the evidence, and the systematic evidence review on the USPSTF Web site (http://www.ahrq.gov/clinic/uspstfix.htm). The summary of the evidence and recommendation statement are available in print by subscription through the AHRQ Publications Clearinghouse (800–358–9295, e-mail,firstname.lastname@example.org).
Copyright © 2005 by the American Academy of Family Physicians.
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