METHODS
Details on the materials, methods, definitions of variables and
statistical approach may be found in the Supplementary Appendix.
Briefly, 905 plasma samples originating from the time of birth (cord
blood, n=376), 1 year (n=195) and 8 years (n=334) from the Manchester
Asthma and Allergy Study (MAAS) were analysed for their chemokine
content (Figure S1). Plasma levels of CCL18 were measured using an
in-house DuoSet ELISA kit (R&D Systems) and an in-house multiplex bead
assay was setup for analysis of circulating CCL17, CCL22, CXCL10 and
CXCL11.
The chemokine levels were thereafter associated to asthma and allergic
sensitisation, and CCL18 levels were additionally related to
multivariable outcomes. To study whether chemokine levels predicted
asthma or allergic sensitisation, binomial logistic regression analyses
were performed on natural log transformed chemokine data. Longitudinal
analyses were performed using generalised estimating equations (GEE).
Population-averaged GEE models were developed to investigate whether the
effect of natural log-transformed chemokine levels on the development of
asthma or sensitisation changed over time. All models were adjusted for
parental atopy, parental smoking and gender. Resulting coefficients
represent the increased/decreased
odds of the respective outcome per log-unit increase in chemokine
levels.
Analyses were conducted in GraphPad Prism 824, IBM
SPSS Statistics version 2525, and Stata 15
software.26