TABLE 2.
Contributions of covariates to variability in the BMI-z5to10 phenotype as determined by using univariate linear regression analysis with the subsequent generation of residual phenotypes (BMI-zadj and BMI-zadjFEV) by using multivariate regression analyses1
| Univariate regression analysis |
Multivariate regression analyses |
|||
| BMI-z5to10 |
BMI-zadj (n = 965) | BMI-zadjFEV (n = 943) | ||
| Coefficient (95% CI) | No. of subjects in the analysis | Coefficient (95% CI) | Coefficient (95% CI) | |
| Female sex | −0.09 (−0.19 to 0.01) | 1124 | −0.12 (−0.23 to −0.02) | −0.15 (−0.25 to −0.05) |
| P | 0.08 | 0.02 | 0.004 | |
| Birth cohort | 0.10 (0.06–0.14) | 1124 | 0.10 (0.06–0.14) | 0.08 (0.03–0.12) |
| P | <0.001 | <0.001 | <0.001 | |
| Age at CF diagnosis | 0.06 (0.01–0.11) | 895 | — | — |
| P | 0.01 | — | — | |
| Diagnosis by NBS | 0.09 (−0.15 to 0.33) | 975 | — | — |
| P | 0.45 | — | — | |
| F508del homozygosity | −0.06 (−0.18 to 0.06) | 1124 | — | — |
| P | 0.33 | — | — | |
| Pancreatic insufficiency | −0.35 (−0.55 to −0.14) | 1124 | −0.33 (−0.53 to −0.13) | −0.32 (−0.52 to −0.12) |
| P | 0.001 | 0.001 | 0.002 | |
| History of MI | −0.19 (−0.33 to −0.05) | 965 | −0.16 (−0.29 to −0.02) | −0.13 (−0.25 to 0.00) |
| P | 0.01 | 0.03 | 0.04 | |
| Presence of a gastrostomy | −0.45 (−0.61 to −0.29) | 918 | — | — |
| P | <0.001 | — | — | |
| FEVq6to10 (/10 percentile points) | 0.10 (0.08–0.13) | 1096 | — | 0.10 (0.08–0.13) |
| P | <0.001 | — | <0.001 | |
| Public insurance | −0.03 (−0.15 to 0.08) | 1055 | — | — |
| P | 0.57 | — | — | |
Coefficient (95% CI) denotes the magnitude of the effect of each covariate with the 95% CI of each coefficient in parentheses. P values are for the significance of the coefficient derived by using linear regression (Stata IC 11 software; StataCorp). BMI-zadj, average BMI z score from 5 to 10 y of age adjusted for female sex, birth cohort, pancreatic insufficiency, and history of meconium ileus; BMI-zadjFEV, average BMI z score from 5 to 10 y of age adjusted as for BMI-zadj plus for FEVq6to10; BMI-z5to10, average BMI z score from 5 to 10 y of age; CF, cystic fibrosis; FEVq6to10, average cystic fibrosis–specific forced expiratory volume in 1 s percentile for all measures obtained from 6 to 10 y of age; MI, meconium ileus; NBS, newborn screen.