TABLE 3

Statistical model estimates

ParametersLinear mixed modelInterpreted estimates
Estimate#95% CIp-valueEstimate95% CI
Mean parameters
 Below 2 weeks of age
  Newborn scheduled measurement (intercept)3.6793.457–3.900<0.000139.6 ppb31.7–49.4 ppb
 Above 2 weeks of age
  Infant scheduled measurement (intercept)4.2764.052–4.500<0.000171.9 ppb57.5–90.0 ppb
  Infant RTI measurement−1.556−1.786 to −1.326<0.0001−78.9%−83.2 to −73.4%
  Infant age months0.0520.037–0.068<0.00015.4%3.7–7.0%
Variance parameters
 Between-subject variance (random intercept)0.0680.029–0.3080.04
 Within-subject variance (residual error)0.490.400–0.607<0.0001

RTI: respiratory tract infection. #: estimated parameters from the linear mixed model used for analysis of log-transformed nasal nitric oxide (NO). Newborn babies only had scheduled measurements. For healthy infants (HI) >2 weeks old only, the model included RTI (yes/no) and age (months). A random intercept for each child was used in the random part of the model. : estimates transformed to the nasal NO scale (a ratio scale, determined as the antilog of the estimated mean parameters, exp(estimate)). Intercepts are to be interpreted as median values whereas differences between groups are reported as percentages.