[The pediatrician and exclusive breastfeeding].

be taken into account. Another relevant factor is that, apart from the quality of the x-rays themselves, the entire assessment was performed under ideal conditions, which makes the study appropriate to assess efficacy and not effectiveness.8 It can be further deduced that, under true working conditions, with time scarce and less wellqualified personnel, that interobserver variation would be greater still. As the group of children studied were all hospitalized, the external validity of this research is limited to more serious cases and cannot be extrapolated to cover outpatients treatment.