Analysis of association between covariates and repeated measurements of forced expiratory volume in 1 s % predicted, from multilevel models
Covariate | B coefficient (95% CI)# | p-value | p-value from likelihood ratio test for interaction with age¶ | Patients included in analysis+ |
Sex | 4.02 (−4.02–12.05) | 0.33 | 108 | |
BMI | 0.31 (−0.17–0.79) | 0.21 | 108 | |
Age at diagnosis | 0.001 (−0.35–0.35) | 1.00 | 59 | |
Nasal nitric oxide | 0.10 (−0.01–0.22) | 0.09 | 68 | |
Ciliary beat frequency | 6.47 (−15.76–2.82) | 0.17 | 101 | |
Pseudomonas aeruginosa | −0.37 (−2.37–1.63) | 0.72 | 107 | |
Ciliary ultrastructure by TEM | 0.03§ | 0.04 | 97 | |
Normal or inconclusive | 0.00 | |||
Outer±inner arm defect | 3.90 (−7.01–14.80) | |||
Microtubular defects | 10.29 (−23.59–3.01) | |||
Extent of bronchiectasis | −0.18 (−0.41–0.05)ƒ | 0.122 | 0.03 | 68 |
Severity of bronchial wall dilatation | −0.17 (−0.36–0.02)ƒ | 0.08 | 0.01+ | 68 |
Bronchial wall thickness | −0.29 (−0.56– −0.01)ƒ | 0.045 | 0.06+ | 68 |
Small airway plugging (continuous) | −0.29 (−0.46– −0.13)ƒ | <0.001 | 0.196+ | 68 |
Large airway plugging | −0.63 (−1.08– −0.17)ƒ | 0.007 | 0.19+ | 68 |
Mosaicism | −0.26 (−0.46– −0.07)ƒ | 0.008 | 0.16+ | 68 |
BMI: body mass index; TEM: transmission electron microscopy. #: B coefficients are to be interpreted as the change in forced expiratory volume in 1 s (FEV1) for each unit change of the covariate after adjusting for age at which the measurement was made; ¶: tests for interaction with age assess whether these covariates affect how FEV1 changes as patients get older; +: patients included in each of these regression analyses had non-missing data for FEV1, age at the time the FEV1 measure was taken, the covariate under study, and ciliary ultrastructure where this was adjusted for; §: the p-value for this covariate relates to the covariate as a whole rather than one level or another; ƒ: after additionally adjusting for ciliary ultrastructure.