The aims of this study were (1) to develop and validate the interactive CLAIM Test (iCLAIM Test) to measure children’s ability to assess claims about treatment effects and make informed health choices and (2) to measure this ability in Spanish primary school children using the developed test.

We followed a multistep process including (1) definition of the test scope, (2) selection of the questions, (3) translation process, (4) design and development of the online test, (5) external review with experts, (6) user-test with children and (7) cross-sectional validation study with Rasch analysis.

Spanish primary schools.

Twelve experts (75% women) participated in the review, 11 children (45% girls) participated in the user-test and 480 Spanish primary school children (46.5% girls) from fourth to sixth grades (9–12 years old) participated in the cross-sectional validation study.

The iCLAIM Test is an online, interactive and user-friendly test in Spanish that measures children’s ability to understand and apply key concepts of the informed health choices (IHC) Project when assessing claims about treatment effects and making IHCs. The test includes 30 questions: six demographic questions and 24 questions from the Claim Evaluation Tools item bank. Less than 40% of the students who participated in the cross-sectional validation study showed basic knowledge of the IHC Key Concepts and how to apply them, and less than 4% showed a clear knowledge. The test showed a good fit to the Rasch model and was acceptable to the target audience.

The iCLAIM Test is the first instrument validated for measuring children’s ability to assess treatment claims in Spain. In the future, we can tailor IHC education interventions and improve critical thinking skills about the health of Spanish children.