Validation of a new concept: aptitudes of psychiatric nurses caring for depressed patients

Validation is vital for operationalising a new concept into a measurement instrument. The measurement of human attributes is usually done with questionnaire items in ordered categories. Our objective was to validate a questionnaire capable of measuring, at the ordinal level, the aptitude of psychiatric nurses caring for depressed patients. We used expert panels, experimentation, categorical principal component analysis, and parametric and non-parametric item response theory to develop such a questionnaire and assess its validity. Expert panels delineated five aspects and 29 components of aptitude and formulated 32 items. Four consecutive exploratory experiments were performed to gauge and calibrate the items and their response categories into a semantic frame of reference and a socio-cultural and job context of nurses. This resulted in a questionnaire comprising three aspects of aptitude. Fourteen questionnaire items with a different number of response categories assessed aptitude. Appropriate techniques shed light onto how nurses understand and respond to items in the questionnaire. Before it can be reliably used in a different context, the questionnaire needs to be re-evaluated for validity. Moreover, validity needs to be re-established for translated versions. In conclusion, validation is a process. Understanding that the scope and limitations of a questionnaire develop as it is being used requires validity to be re-established at each step of development