Red cell distribution width in subclinical hypothyroidism.

e have read the article “The value of red blood cell distribution width (RDW) in subclinical hypothyroidism” by Hea Min Yu and cols. (1). They aimed to investigate the relationship between the subclinical hypothyroidism and RDW levels in a healthy population. They concluded that RDW levels were correlated with euthyroid and subclinical thyroid status. This study gives important information on this clinically relevant condition. Thanks to the authors for their contribution. We think that some points should be discussed. Some markers have been found to be associated with early and late complications in many conditions. Inflammatory cytokines, high-sensitivity C-reactive protein (CRP), natriuretic peptides, neurohormones have recently established to be useful markers for diagnosis and prognosis in many diseases. However, these markers are very expensive and are not easily used in clinical practice. Elevated RDW is a measure of the variabi-lity in size of circulating erythrocytes and is expressed as the coefficient of variation of the erythrocyte volume. As several routine haematology instruments can analyse erythrocyte volume, RDW is available in most clinical settings. The ready availability of this parameter without additional cost may encourage its wider use in clinical pra-ctice. Several studies have reported that elevated RDW levels are associated with poor prognosis in the setting of atherosclerosis, heart failure, stroke, peripheral arterial dis -ease, older age (2). However, RDW may also reflect ethnicity, neurohumoral activa-tion, renal dysfunction, hepatic dysfunction, nutritional deficiencies (i.e. iron, vitamin B