Development and validation of a new Prescription Quality Index

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • Many studies raise serious questions about the prescribing appropriateness and prescription quality. However, there is a lack of a single measure that will capture all facets of prescription quality. • Evaluation of prescriptions was usually based on expert judgement of practitioners. • Definition of prescription quality, reference model, validity and reliability of the measurement tools, and other data such as the number, type and severity of diagnosis of patients were usually insufficient or lacking. WHAT THIS STUDY ADDS • The Prescription Quality Index (PQI) was developed with a strong structural foundation and was able to capture the clinical, clerical and legal requirement of a prescription. • Extensive psychometric testing was performed on the PQI and the new tool demonstrated acceptable validity and reliability. • The PQI has been shown to be a valid, reliable and responsive tool to measure quality of prescriptions in chronic diseases. AIMS The aims were to develop and validate a new Prescription Quality Index (PQI) for the measurement of prescription quality in chronic diseases. METHODS The PQI were developed and validated based on three separate surveys and one pilot study. Criteria were developed based on literature search, discussions and brainstorming sessions. Validity of the criteria was examined using modified Delphi method. Pre-testing was performed on 30 patients suffering from chronic diseases. The modified version was then subjected to reviews by pharmacists and clinicians in two separate surveys. The rater-based PQI with 22 criteria was then piloted in 120 patients with chronic illnesses. Results were analysed using SPSS version 12.0.1 RESULTS Exploratory principal components analysis revealed multiple factors contributing to prescription quality. Cronbach's α for the entire 22 criteria was 0.60. The average intra-rater and inter-rater reliability showed good to moderate stability (intraclass correlation coefficient 0.76 and 0.52, respectively). The PQI was significantly and negatively correlated with age (correlation coefficient −0.34, P < 0.001), number of drugs in prescriptions (correlation coefficient −0.51, P < 0.001) and number of chronic diseases/conditions (correlation coefficient −0.35, P < 0.001). CONCLUSIONS The PQI is a promising new instrument for measuring prescription quality. It has been shown that the PQI is a valid, reliable and responsive tool to measure quality of prescription in chronic diseases.