TY - JOUR T1 - On the diagnosis of subclinical hypothyroidism JF - British Journal of General Practice JO - Br J Gen Pract SP - 1000 LP - 1001 VL - 57 IS - 545 AU - Adel AA Ismail Y1 - 2007/12/01 UR - http://bjgp.org/content/57/545/1000.abstract N2 - Subclinical hypothyroidism is usually an asymptomatic condition, diagnosed when there are no specific symptoms or signs of thyroid dysfunction but the patient has an elevated serum thyroid stimulating hormone (TSH) in the face of normal circulating thyroid hormone levels. The diagnosis is therefore biochemical, based almost entirely on a raised TSH concentration. Furthermore, at TSH concentration of 10mU/L or above, thyroid replacement may be considered.1,2 The prevalence of this condition in different population studies varied from 1% to 17%, with the highest prevalence in the elderly.1,3,4TSH in serum is measured by immunoassay technology which relies on an ‘induced fit’ between the antibody and the antigen. In this interaction, the antibody essentially recognises shape; that is, the antigen three-dimensional shapes plus the electron cloud at the site of binding. For this reason, immunoassay technology is inherently less robust than conventional routine biochemical tests and is more prone to produce analytically wrong results if endogenous interfering antibodies are present. Furthermore, this form of interference could occur despite the strictest laboratory control schemes because interference is unique to a particular sample.5The prevalence of analytical interference leading to erroneous immunoassay results is in all … ER -