Table 2.

Multivariable mixed regression model of longitudinal change in spirometry parameters over time in 197 children with sickle cell anemia enrolled between 4 and 18 years of age, and followed prospectively for a median of 4.7 years in the Sleep and Asthma Cohort (SAC) study

1a. Multivariable model of change in FEV1 %predicted#
Covariate	B	95% CI	P value
Male sex	0.20	−3.15 –   3.56	0.91
Age	−0.30	−0.56 – −0.05	0.02
Asthma	−2.29	−6.05 –   1.48	0.23
Hydroxyurea use	1.14	−0.88 –   3.16	0.27
Hemoglobin at baseline	0.99	−0.46 –   2.44	0.18
White blood cell count at baseline	0.16	−0.32 –   0.65	0.50
Reticulocyte count at baseline	0.13	−0.19 –   0.46	0.41
Pain incidence rate	−0.03	−0.34 –   0.29	0.87
ACS incidence rate	−0.05	−0.87 –   0.77	0.91
1b. Multivariable model of change in FVC %predicted#
Male sex	1.37	−2.21 –   4.94	0.45
Age	−0.20	−0.45 –   0.06	0.13
Asthma	−0.38	−4.41 –   3.64	0.85
Hydroxyurea use	2.12	0.14 –   4.12	0.04
Hemoglobin at baseline	0.98	−0.56 –   2.53	0.21
White blood cell count at baseline	0.22	−0.29 –   0.74	0.40
Reticulocyte count at baseline	0.13	−0.21 –   0.47	0.46
Pain incidence rate	−0.03	−0.34 –   0.27	0.83
ACS incidence rate	−0.60	−1.40 –   0.19	0.14
1c. Multivariable model of change in FEV1/FVC %predicted*
Male sex	−0.74	−2.47 –   1.00	0.40
Age	−0.07	−0.21 –   0.07	0.35
Asthma	−1.74	−3.68 –   0.21	0.08
Hydroxyurea use	−0.45	−1.72 –   0.81	0.48
Hemoglobin at baseline	0.06	−0.70 –   0.81	0.88
White blood cell count at baseline	−0.04	−0.29 –   0.21	0.73
Reticulocyte count at baseline	0.04	−0.13 –   0.20	0.67
Pain incidence rate	0.01	−0.20 –   0.21	0.96
ACS incidence rate	0.34	−0.19 –   0.86	0.21

Abbreviations: ACS=acute chest syndrome; SCA=sickle cell anemia; IRR=incidence rate ratio; CI=confidence interval

^#Includes random intercepts and slopes

^*Includes random intercepts

^*Mann-Whitney U test

^§Mid-p exact test