 The disability classification for each domain with the exception of the cognitive domain was calculated from the answers to questions on the HSQ or the PQ see INIS Collaborative Group 2011 online supplement for more detail. If one questionnaire was missing, the calculation used only the answer on the other questionnaire. If the domain classification was unknown and a SHSQ had been received, the classification from that questionnaire was used for that domain only. Cognitive function was assessed in INIS by parents using the revised Parent Report of Childrens Abilities questionnaire PARCA-R1 Saudino 1998, as described previously INIS Collaborative Group 2011 online supplement. 