Table 6.

ITPA Variants and ITPase Deficiency Are Associated With a Reduction in the Week 4 Hb Level: Multivariate Logistic Regression Modeling of Qualitative Week 4 Anemia (Hb Reduction > 3 g/dL)

ITPA Variant	Odds Ratio	95% CI	P Value
rs1127354	0.051	0.006–0.46	0.0082
rs7270101	0.141	0.04–0.46	0.0012
ITPA Variant	Adjusted Odds Ratio*	95% CI	Adjusted P Value*
rs1127354	0.033	0.003–0.33	0.0039
rs7270101	0.106	0.03–0.38	0.0006
ITPase Deficiency Variable	Odds Ratio	95% CI	P Value
Grade 0/1/2/3	0.137	0.05–0.35	3.52 × 10−5

The two ITPA variants were strongly and independently associated with protection from Hb reduction > 3 g/dL in week 4. The strength of association of the ITPase deficiency variable with week 4 anemia was greater than that for either ITPA variant alone (the complete multivariate logistic regression model, including odds ratios for all variables, is shown in Supporting Information Table 2). The covariates were age, sex, body mass index, baseline Hb level, baseline glomerular filtration rate, METAVIR F3–F4 versus F0–F2, and RBV starting dose (mg/kg). Neither the HCV RNA level nor the HCV genotype was significantly associated with Hb reduction in univariate analyses.

^*Adjusted odds ratios and independent P values were calculated with models in which the other functional variant was already included.