American Society for Clinical Laboratory Science

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September 13, 2021

Do not use serum cortisol levels as initial screening for adrenal hyperfunction [Cushing syndrome], instead consider superior strategies provided in the justification.

Serum cortisol levels do not provide high-end diagnostic accuracy or sensitivity when used as an initial diagnostic test. Late night salivary cortisol samples employing an approved collection device, 24-hour urine free cortisol [UFC], or a 1 mg overnight dexamethasone suppression test [DST] should be used as an initial test. These tests have a high diagnostic accuracy for Cushing syndrome [CS]. Multiple screening tests may need to be performed based on the variability of hypercortisolism in CS. Two measurements of abnormal cortisol levels with these tests are recommended for an initial diagnosis, further workup should be referred to an endocrinologist to make the final diagnosis. Each of these tests has different limitations and should be chosen based on the lifestyle and medical history of the patient. Patients with erratic sleep schedules or shift workers would not obtain accurate results from a late-night salivary cortisol test. Women taking oral estrogen, those taking antiepileptic drugs [phenytoin and phenobarbitone], and pregnant women could have falsely elevated cortisol levels as CYP3A4 metabolizes dexamethasone with the DST. UFC tests require rigorous collection management and should not be used on patients experiencing renal failure, or those suspected to have mild CS. Exogenous glucocorticoid use must be excluded before performing these biochemical tests.

These items are provided solely for informational purposes and are not intended as a substitute for consultation with a medical professional. Patients with any specific questions about the items on this list or their individual situation should consult their physician.

How The List Was Created

George Fritsma, MS, MLS (ASCP), and the late Cindy Johns, MS, MLS (ASCP) hosted a plenary presentation “Enhancing Laboratory Communication to Reduce Extra-analytical Errors” at the ASCLS Clinical Laboratory Educators’ Conference in Boston in February 2017. Their talk referenced the ABIMF Choosing Wisely initiative. Subsequent discussions resulted in the ASCLS Board of Directors appointing a Choosing Wisely task force that evolved to a standing committee. The committee is composed of ASCLS members representing all medical laboratory science disciplines.

The committee collaborated with respective ASCLS Scientific Assemblies in developing and reviewing recommendations, which the Board of Directors reviewed and accepted for publication. The recommendations were subsequently reviewed in collaboration with the ASCP Test Utilization Steering Committee prior to submission.



American Society for Clinical Laboratory Science (ASCLS) recommendations were developed under the leadership of ASCLS’s Choosing Wisely Committee and the ASCLS president and executive vice president. The Committee examined numerous options based on evidence available through an extensive review of  the literature and member proposals. Subject matter experts from the ASCLS Scientific Assemblies reviewed and recommended approval of their respective recommendations, which are subsequently approved by the ASCLS Board of Directors. The recommendations were subsequently reviewed in collaboration with the ASCP Test Utilization Steering Committee prior to submission.


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