LOW ERYTHROPOIETIN LEVELS IN CYSTIC-FIBROSIS

Polycythemia is the usual compensatory response to chronic tissue hypo xia. Despite tissue hypoxia, patients with cystic fibrosis (CF) are fr equently anemic and almost never polycythemic. We measured the blood l evels of hemoglobin (Hg) and erythropoietin (EPO) in anemic and nonane mic patients with CF. These levels were then compared to normal and an emic control subjects. The central venous oxygen content (CvO(2)), par tial pressure of oxygen (PvO(2)), and percent hemoglobin-oxygen satura tion (SvO(2)) were then correlated with EPO levels in anemic patients with and without CF. The EPO levels of patients with CF and anemia wer e significantly lower than those of control subjects with the same deg ree of anemia (12.39+/-1.49 versus 60.94+/-23.65; p <0.05) and were no t significantly different from those of nonanemic patients with CF and normal subjects. EPO levels in nonanemic patients with CF did not dif fer from those of normal subjects. The National Institutes of Health ( NIH) scores (disease severity) were lower in the anemic CF group than in the nonanemic group of patients with CF. CvO(2), PvO(2), and SvO(2) were significantly lower in the anemic CF group than in the control g roup with anemia (8.2 versus 10.2 ml/dl, 32 versus 40 mm Hg and 57 ver sus 71%, p <0.01). EPO levels were lower in the CF group but not signi ficantly; Albumin levels were lower in the anemic CF group than in the control group with anemia (3.12+/-0.09 versus 4.0+/-0.10; p <0.01). V itamin levels and iron storage were in the normal range or higher in b oth groups of patients. EPO levels were lower in the anemic CF patient s despite the presence of tissue hypoxia. The presence of anemia in so me of our CF patients may be related to inadequate EPO production, sin ce iron stores and vitamin levels were adequate for bone marrow produc tion. The low EPO levels could be secondary to malnutrition, since the CF group with anemia had lower albumin levels and lower NIH scores. O ur data indicate that when CF becomes more severe, the expected increa se in EPO production in response to chronic tissue hypoxia is not suff icient to meet the demands for red cell production.