Quality of life in childhood immune thrombocytopenia: International validation of the kids’ ITP tools

Abstract
Background
The Kids ITP Tools (KIT) is a disease‐specific measure of health‐related quality of life for children with immune thrombocytopenia (ITP). To facilitate use in international trials it has been cross‐culturally adapted for France, Germany, the United Kingdom and Uruguay. This study assessed the validity and reliability of the translated KIT in comparison to generic quality of life measures.

Methods
Children 2–18 years of age with ITP and their parents were recruited in France, Germany, the United Kingdom and Uruguay. Participants completed the KIT, PedsQL and KINDL. We examined the Pearson’s correlation between these measures for our pooled sample and estimated the reliability over a 2‐week time period. Findings were further explored by country.

Results
A total of 127 families (81 children self‐reported) participated. Mean child‐reported scores were: KIT 74.3 (SD = 15.3), PedsQL 81.3 (SD = 13.0), and KINDL 70.5 (SD = 14.3). Corresponding mean parent proxy‐reported scores were: 70.6 (SD = 18.1), 75.7 (SD = 16.8) and 72.3 (SD = 12.7), respectively. Correlation between KIT and the generic measures was consistent with our a priori hypothesis (PedsQL r = 0.54, KINDL r = 0.48, both P  < 0.0001). Child KIT scores for newly diagnosed ITP patients were significantly lower than for chronic ITP patients (67.3 vs. 77.3; P  = 0.005). There was a significant correlation (P  < 0.001) between the child and parent proxy KIT scores (ICC = 0.52). Child KIT test‐retest reliability was acceptable at 0.71.

Conclusions
The cross‐culturally translated KIT is valid and reliable with acceptable correlation to the PedsQL and KINDL. There is a significant difference in child self‐reported KIT scores between newly diagnosed and chronic ITP.