Strengths and weaknesses
Our study has several strengths. First, it is based on a large
population of children and adults covering a wide range of ages (range:
2-80), with detailed assessment of both RSV and RV-specific IgG levels
and personal factors. Moreover, this population includes a subpopulation
of individuals with respiratory viruses IgG assessment in both childhood
and early adulthood allowing to specifically characterize change in IgG
levels at the individual level over time. Novel and validated
micro-array techniques were used to assess IgG levels. Then, different
antigens were studied, related to two different respiratory viruses, RSV
and RV. For RV, the analyses were based on micro-arrayed VP1 N-terminal
peptides from a panel of the most representative RV strains covering the
three genetic species.
We acknowledge that our study also suffers from some limitations. First,
we did not have any information about the number of infections or the
time at which viral infection occurs. Consequently, we were unable to
assess the time elapsed between the last viral infection and the time of
blood sampling. Secondly, some personal factors, like genetic factors
which could interact with personal factors, were not considered in this
analysis, and should deserve further investigation but are out of the
scope of the present study. Furthermore, the large majority of our
population is Caucasian, and generalization of our results to other
ethnic groups cannot be done, but allows analyzing a homogenous
population, therefore limiting risk for confounding bias. Additionally,
one has to consider that a percentage of subjects (≥ 55%) had an
allergic sensitization. Finally, given the EGEA study design, asthma
could be considered as a collider bias and may distort the association
investigated (40). However, the fact that all the patterns of
associations reported in this study were stable regardless of the asthma
status supports the absence of collider bias in our results.