Clsi Ep28 -

Mrs. Eleanor Park, 68, came in for fatigue. Her TSH was 3.9 mIU/L—within the manufacturer’s range but above Aliyah’s verified upper limit of 3.2. Using the lab’s new narrow interval, the computer flagged it as Abnormal-High . The junior resident started her on low-dose levothyroxine.

So when the new automated immunoassay analyzer arrived, she knew the drill. The manufacturer’s reference intervals for thyroid-stimulating hormone (TSH) were neatly printed in the manual: 0.4–4.0 mIU/L. But EP28 was clear: Verify before use. Don’t trust, verify. clsi ep28

“Reference intervals may need to be partitioned by age, sex, or other factors… especially for analytes like TSH, where values increase with age.” Mrs. Eleanor Park

Mrs. Park wasn’t abnormal. Aliyah’s reference population was just too young. clsi ep28