The systematic review and meta-analysis performed by Tasche and colleagues1 appears to have been carried out with commendable thoroughness. The results seem clear cut: sodium cromoglycate is ineffective as maintenance therapy in children with asthma. However, their conclusions are not objective but depend in the final analysis on their multivariate regression model. Perhaps this is where the most important bias has crept into the analysis.

As in the case of many new drugs, clinical trials are first carried out in adults, later in schoolchildren, and finally (if ever) in infants and pre-schoolchildren. This appears to have been the …