To the Editor:Recently, the original article entitled "Red Cell Distribution Width Is a Risk Factor for Hip Fracture in Elderly Men Without Anemia" reported by Kim and colleagues attracted our interest. (1) They found that red cell distribution width (RDW) value was significantly associated with future hip fracture risks in older men without anemia. We thank the authors for their valuable contribution to the literature, but we would like to mention a few important points.RDW is a laboratory index that measures the size change of circulating red blood cells, and its importance by physicians has increased in recent years. (2) Although in previous years it was used in the diagnosis of anemia, in recent years it has been emphasized that it is an independent prognostic marker for mortality, especially in patients with cardiovascular and gastrointestinal system diseases. (3,4) RDW can be affected by many situations. These are mainly ethnicity, thyroid disease, nutritional (folate, vitamin B12, and iron deficiency) conditions, bone marrow dysfunction, malignancy, inflammatory diseases, drug use that may affect hematological parameters, renal dysfunction, and hepatic dysfunction. (5,6) It would have been useful if the authors had also reported the effect of these factors, and it is a confusing source of bias. Although it is believed RDW can be used in the follow-up and treatment of many diseases with its applicability, it appears that prospective, multicenter studies are needed for its use in trauma patients.