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Don’t take Cushing’s syndrome screening guidelines literally: study

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – Widespread screening of overweight and obese adults for Cushing’s syndrome is not supported by a new study, even when one or more features of Cushing’s syndrome are present.

“Broad screening programs for Cushing’s syndrome in an obese population would likely lead to unnecessary testing, false-positive results and anxiety,” Dr. Smita K. Baid of the National Institutes of Health, Bethesda, Maryland and colleagues report in the October issue of the Journal of Clinical Endocrinology and Metabolism.

Using tests and criteria recommended by recent Endocrine Society guidelines for screening for Cushing’s syndrome, the research team “found no subject with the disorder among 369 people who were overweight or obese with a mean of five to six signs or symptoms” of the disorder, according to their report.

All subjects completed two or three tests: a 24-hour urine cortisol, and/or late-night salivary cortisol, and/or 1 mg dexamethasone suppression test (DST). An abnormal result on any of these tests triggered a repeat test and/or a dexamethasone-CRH test. Subjects with abnormal DST results and a low dexamethasone level were asked to repeat the test with 2 mg dexamethasone.

The guidelines suggest that Cushing’s syndrome should not be diagnosed unless two tests are abnormal. When the investigators applied this rule, the combined specificities of double combinations of urine free cortisol, DST, and/or salivary cortisol for excluding Cushing’s syndrome ranged from 84% to 90%. The specificity of urine free cortisol, DST and salivary cortisol together was 78%.

While roughly one fourth of the study subjects had at least one abnormal result, mean composite scores among subjects with and without test abnormalities were not significantly different, the investigators report.

This, they say, “highlights the difficulty in determining whom to screen and supports the fact that these screening tests were falsely positive.”

“We caution against a literal interpretation of the recent guidelines,” the authors write. Instead, they suggest that patients be monitored for worsening symptoms over time and then screened, if appropriate.

“Clinical judgment, taking into account the number and progression of symptoms, remains essential for the diagnosis of Cushing’s syndrome,” the researchers conclude.

J Clin Endocrinol Metab 2009;94:3857-3864.