Statistical analysis
Continuous variables were expressed in terms of mean, median, standard deviation and range. Categorical variables were presented using frequency and percentages. Chi-square test was used to compare severe infection, infection involving respiratory system, infection involving systems other than respiratory system, between children with normal immunoglobulin levels and hypoglobulinaemia and different age groups and risk groups. Logistic regression analysis was performed to find the risk of severe infection with respect to different parameters. P-value <0.05 was considered as significant.