Incorrect diagnosis of thyroid disease by junior doctors

Thyroid function tests (TFTs) are commonly performed on elderly patients admitted to hospital. Several diseases and commonly used drugs may alter thyroid function test results. We assessed the knowledge of such interactions among 50 junior doctors in our departments: 60% were unaware that (in our laboratory) the normal range for TFTs is the same in those above 65 years as in those below; 72% correctly noted the effect of an acute illness, while only 48% correctly noted the effect of a chronic illness on test results; 72% were well aware of common drug effects such as those of the oral contraceptive pill, but only 22% and 42% knew of the potentially more important interactions in the elderly with the salicylates and phenytoin respectively. Thyroid screening in elderly people is important. The knowledge of interactions between drugs, disease states and the normal range of biochemical assays used in routine thyroid screening needs to be improved if thyroid function tests are to be interpreted appropriately.