. Author manuscript; available in PMC: 2012 Mar 24.

Published in final edited form as: Kidney Int. 2011 Aug 17;80(9):992–999. doi: 10.1038/ki.2011.247

Table 3.

Association of variant hemoglobin and higher-dose ESA^a

	Univariate analysis		Multivariate analysis^b		Simplified analysis^c
	OR (95% CI)	P-value	OR (95% CI)	P-value	OR (95% CI)	P-value
Logistic regression
Variant Hgb	2.05 (0.92–4.56)	0.08	3.31 (1.20–9.11)	0.02	3.02 (1.26–7.25)	0.01
	IRR (95% CI)	P-value	IRR (95% CI)	P-value	IRR (95% CI)	P-value
Poisson regression
Variant Hgb	1.60 (0.98–2.64)	0.06	1.94 (1.16–3.25)	0.01	2.03 (1.24–3.31)	0.005

Abbreviations: CI, confidence interval; ESA, erythropoiesis-stimulating agent; HbAS, hemoglobin S trait; OR, odds ratio.

Hemoglobin variants included sickle cell trait (HbAS) and hemoglobin C trait. Higher-dose erythropoiesis-stimulating agent defined as ≥6500 U/treatment (≥19,500 U/week). Poisson regression used to more closely approximate risk ratio as odds ratio as determined by logistic regression likely overstates effect estimate, as outcome was common (29.9%).

Multivariate analysis from fully adjusted model—adjusted for percent of missed treatments, albumin, dialysis access, dialysis vintage, Kt/V, ferritin, iron saturation, intact parathyroid hormone, dialysis unit, history of gastrointestinal bleeding, and iron dose per treatment.

Simplified analysis or ‘final model’ derived from full model with removal of covariates by backward elimination via change in estimate testing—adjusted for percent of missed treatments, albumin, and dialysis access.