(Updated March 26) The US Preventive Services Task Force (USPSTF) has again concluded there is insufficient evidence to recommend screening for thyroid dysfunction in adults who are not pregnant and who are asymptomatic, according to an article published online March 23 in the Annals of Internal Medicine.
This recommendation follows on the heels of a similar recommendation published October 27, 2014, in the same journal, in which the USPSTF also concluded there was insufficient evidence to make any recommendation for or against thyroid screening in asymptomatic adults. They also had made the same recommendation 10 years earlier.
"While screening and treating asymptomatic adults for thyroid dysfunction is common, there is very limited evidence that evaluates whether these practices lead to improved health outcomes," task force member Jessica Herzstein, MD, MPH, said in a USPSTF statement.
"I think the task force is correct and did an excellent job reviewing the literature and coming to a reasonable conclusion," Kenneth Burman, MD, chief, endocrinology section, MedStar Washington Hospital Center, Washington, DC, told Medscape Medical News.
"But that is different than an individual patient being seen by a primary care physician, and if a patient has symptoms that may be compatible with thyroid disease, whether it's hypo- or hyperthyroidism, then appropriate laboratory tests should be performed."
Clinically Meaningful Benefits Unclear
The USPSTF members also found there was insufficient evidence that screening for thyroid dysfunction in asymptomatic nonpregnant adults leads to any clinically important benefits.
In contrast, "indirect evidence points to the likelihood of important and frequent harms associated with screening in asymptomatic persons," write Michael L LeFevre, MD, MSPH, and colleagues on behalf of the USPSTF.
Foremost among these harms are frequent false-positive results and the psychological burden of labeling someone with a disorder.
The task force members also feel that much of the overdiagnosis and overtreatment of thyroid dysfunction occurring in the United States is likely the consequence of screening, particularly because thyroid dysfunction is defined by silent biochemical parameters and not a set of reliable and consistent clinical symptoms.
In 2013, a single name brand of thyroid hormone was the most commonly prescribed drug in the United States.
To inform their updated recommendation, researchers reviewed both randomized controlled trials, as well as observational studies, of screening and treatment published through July 2014.
No trials directly assessed the benefits and harms of screening for thyroid dysfunction vs no screening.
The task force found adequate evidence that screening can detect "abnormal" serum thyroid-stimulating hormone (TSH) levels in asymptomatic patients.
"However, what constitutes an abnormal TSH level is uncertain," task force members write.
Members also suggested there is professional disagreement about the appropriate cut points for lower and upper boundaries of normal TSH levels, both in the general population and in subgroups, such as older adults, where values differ from the overall population.
"Many people can have slight abnormalities in their thyroid test and not experience any symptoms," task-force co–vice chair Kirsten Bibbins-Domingo, MD, PhD, pointed out in a USPSTF news release.
In contrast, Dr Burman argued that the normal TSH range is well established, although he agrees that it has not been proven that a mildly abnormal TSH is associated with any significant medical issue.
"There is also a difference between obtaining enough credible evidence to recommend screening for an adult population, whether they are pregnant or not, as compared to case findings, and case findings are more relevant for individual patients who are being seen by individual physicians, generally for a particular symptom," Dr Burman said.
Dr Burman noted, too, that the elderly, especially those older than 80 and 90 years, have different normal TSH values from those of younger adults and may require special consideration.
Aggressive Case Finding Should Be the Norm
Indeed, both the American Thyroid Association and the American Society of Clinical Endocrinology recommend that physicians consider screening for hypothyroidism in patients older than 60 years, as well as taking an aggressive case-finding approach in patients who are at risk for hypothyroidism and for women who are planning pregnancy.
The American Association of Clinical Endocrinology agrees and is stressing that "aggressive case finding" is an appropriate alternative in certain patient groups that are at highest risk "for developing life-altering overt thyroid disease." These include:
Patients over 60, in whom symptoms of hypothyroidism are often minimal, absent, or atypical.
Newborns (continued mandatory screening for congenital hypothyroidism recommended).
Those with autoimmune disease often associated with thyroid disease (eg, type 1 diabetes).
Patients with a prior history of thyroid disease or thyroid surgery or an abnormal thyroid exam or who are taking drugs known to affect the thyroid.
Patients with a family history of thyroid illness.
AACE president R Mack Harrell, MD, from Memorial Health Systems, Florida, said: "My fear is that the USPSTF's statement about a 'lack of data' to justify thyroid-disease screening will be incorrectly interpreted as a 'lack of clinical need' to find and treat thyroid disease.
"We've come a long way with diagnosis and treatment of thyroid disease over the past 90 years, and we don't need to return to the bad old days," he stressed.
Dr Burman said: "The task force recommendation does not change my practice, because obviously it is a referral practice, and most patients come with a potential thyroid disorder.
"However, I think the [USPSTF] recommendation supports in general what the primary care physician is already doing, or should be doing, and that is asking patients appropriate questions and assessing them for signs or symptoms of hypothyroidism, and then assessing thyroid function where appropriate," he added.
Symptoms May Differ Now
Separately, a new paper in Family Practice, published online March 17, has found that the symptoms associated with thyroid disease in one GP practice in the United Kingdom differed from those generally reported as being associated with hypothyroid.
Drs Alexander Werhun and William Hamilton of University of Exeter Medical School, United Kingdom, examined the primary care records relating to every TSH test taken over a year from August 2012.
There were 2035 patients (12% of the practice population) who had TSH testing that year — of these, 35 (1.7%) had a TSH > 4.5 mIU/L, suggesting hypothyroidism, and seven (0.3%) had TSH < 0.01 mIU/L, suggesting hyperthyroidism.
Features associated with an abnormal TSH were pregnancy (odds ratio [OR], 41), constipation (OR, 9.7), palpitations (OR, 23), hair loss (OR, 21), weight gain (OR, 18), and diarrhea (OR, 13). In a separate analysis, only pregnancy and constipation were associated with a raised TSH, and the remaining features with a low TSH.
The symptoms associated with thyroid disease differ from those generally reported, say Drs Werhun and Hamilton, which they suggest could be because fewer patients are now presenting with advanced thyroid disease.
The upshot is that thyroid testing could be better targeted without missing diagnoses, they conclude.
"Otherwise Asymptomatic" Is Problematic in the Elderly
Mark Williams, MD, clinical professor of medicine, University of North Carolina School of Medicine, Wilmington, and professor emeritus of geriatric medicine, University of Virginia Health System, Charlottesville, told Medscape Medical News he also thinks there is not enough evidence to screen completely asymptomatic patients younger than 65 years who are not pregnant. That said, he notes that the task force did not bracket their recommendation with any age limit.
"For me, as a practicing geriatrician, the term 'otherwise asymptomatic,' which the task force uses, is problematic," Dr Williams said.
Thyroid disease is notorious for producing vague nonspecific symptoms such as fatigue, loss of energy, mental slowness, and apathy, he said.
"Since we all have ups and downs, what is symptomatic and what isn't?" Dr Williams asked.
It is also not uncommon for him to see an elderly person with significant hypothyroidism that had been written off as an insidious decline in function resulting from old age.
"I think the task force is correct not to mandate thyroid function tests as part of screening in completely asymptomatic, vigorous, nonpregnant adults [younger than 65 years]," Dr Williams said.
"However, the risks [of thyroid function screening] are very low, and the benefits are potentially great, so astute clinicians may consider thyroid function tests when they individualize care."
Dr Burman has disclosed no relevant financial relationships. Dr Williams has served as a director, officer, partner, employee, advisor, consultant, or trustee for BioMotion Analytics. Drs Werhun and Hamilton declare they have no relevant financial relationships.
Ann Intern Med. Published online March 23, 2015. Full text
Fam Pract. Published online March 17, 2015. Abstract
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Cite this: USPSTF: Thyroid Screens Not Supported in Asymptomatic Adults - Medscape - Mar 24, 2015.