Dear Editor,

We have recently [1] read Sim et al's article entitled “Vitamin D deficiency and anemia: a cross-sectional study”.

Although most of the myelofibrosis with anemia in children reported by us [2–4] was due to 25 hydroxy cholecalciferol (25 OH CC; 25OH D3) deficiency, we could not find correlation between anemia and rickets due to 25 OH CC deficiency, which is in contrast to the authors' findings [5].

We suspect that the author's findings of anemia in patients with low level 25 OH CC was related mostly to renal insufficiency. Since eGFR was less than 60 mL/min/1.72 m2 more often in the low 25 OH (<30) group (80.8%) than in the control group (53.2%), while more frequent in patients with diabetes (65.4% vs 43.0%; p < 0,01). Erythocyte-stimulating agents were also prescribed more often for this group (p < 0,01).

We wish that the authors had also determined calcium, phosphorus, 1,25 dihydroxy cholecalciferol (1,25 (OH)2 CC), and parathormone levels in their patients.

Therefore, we believe that the correlation should be extrapolated in patients without renal insufficiency.