Table 3. Regression coefficients for unadjusted and adjusted models of EPO levels by etiology.

Unadjusted modela
Etiology of the anemia	R2adj	Coefficiente	95% CI	p-value
Chronic kidney disease	0.214	0.29	0.18, 0.48	< 0.001 f
Chronic disease	0.137	0.42	0.27, 0.66	< 0.001 f
Myelodysplastic syndrome (confirmed)	0.019	1.65	1.08, 2.51	0.020 f
Myelodysplastic syndrome (suspected)	-0.010	1.04	0.54, 2.01	0.898
Myelodysplastic syndrome (all)	0.014	1.58	1.04, 2.40	0.031 f
Anemia of unknown etiology	0.148	0.43	0.31, 0.58	< 0.001 f
Other etiology	0.006	1.40	0.89, 2.20	0.151
Multifactorial etiology	0.031	0.54	0.29, 1.04	0.065
Model adjusted for hemoglobinb
Etiology of the anemia	R2adj	Coefficiente	95% CI	p-value
Chronic kidney disease	0.338	0.29	0.19, 0.46	< 0.001 f
Chronic disease	0.357	0.49	0.33, 0.72	< 0.001 f
Myelodysplastic syndrome (confirmed)	0.324	1.30	0.91, 1.84	0.147
Myelodysplastic syndrome (suspected)	0.346	1.13	0.67, 1.92	0.638
Myelodysplastic syndrome (all)	0.332	1.28	0.91, 1.80	0.161
Anemia of unknown etiology	0.339	0.61	0.46, 0.82	0.001 f
Other etiology	0.320	1.21	0.83, 1.76	0.322
Multifactorial etiology	0.386	0.48	0.29, 1.24	0.006 f
Model adjusted for hemoglobin and eGFRc
Etiology of the anemia	R2adj	Coefficiente	95% CI	p-value
Chronic kidney disease	0.389	0.52	0.29, 0.92	0.025 f
Chronic disease	0.421	0.54	0.37, 0.77	0.001 f
Myelodysplastic syndrome (confirmed)	0.387	1.30	0.93, 1.82	0.118
Myelodysplastic syndrome (suspected)	0.421	1.14	0.69, 1.87	0.600
Myelodysplastic syndrome (all)	0.393	1.29	0.93, 1.79	0.130
Anemia of unknown etiology	0.410	0.73	0.55, 0.97	0.028 f
Other etiology	0.419	1.09	0.77, 1.56	0.626
Multifactorial etiology	0.509	0.78	0.47, 1.30	0.345
Model adjusted for hemoglobin, eGFR and comorbidity indexd
Etiology of the anemia	R2adj	Coefficiente	95% CI	p-value
Chronic kidney disease	0.405	0.49	0.28, 0.87	0.015 f
Chronic disease	0.432	0.51	0.36, 0.74	0.001 f
Myelodysplastic syndrome (confirmed)	0.386	1.29	0.92, 1.81	0.134
Myelodysplastic syndrome (suspected)	0.419	1.19	0.72, 1.97	0.500
Myelodysplastic syndrome (all)	0.392	1.27	0.92, 1.77	0.150
Anemia of unknown etiology	0.417	0.72	0.55, 0.96	0.025 f
Other etiology	0.416	1.09	0.76, 1.55	0.636
Multifactorial etiology	0.506	0.74	0.43, 1.26	0.262

^a Unadjusted model: ln EPO = B ∙ etiology

^b Model adjusted for hemoglobin: ln EPO = B ∙ etiology + C₁ ∙ Hb

^c Model adjusted for hemoglobin and eGFR: ln EPO = B ∙ etiology + C₁ ∙ Hb + C₂ ∙ eGFR

^d Model adjusted for hemoglobin, eGFR and comorbidity index: ln EPO = B ∙ etiology + C₁ ∙ Hb + C₂ ∙ eGFR + C₃ ∙ comorbidity

^e The etiology coefficient has been back-transformed using the exponential function (e^B) and thus values represent the ratio of EPO for each given etiology relative to the reference group

^f p<0.05