A scoping review to create a framework for the steps in developing condition-specific preference-based instruments de novo or from an existing non-preference-based instrument: use of item response theory or Rasch analysis.

BACKGROUND: There is no widely accepted framework to guide the development of condition-specific preference-based instruments (CSPBIs) that includes both de novo and from existing non-preference-based instruments. The purpose of this study was to address this gap by reviewing the published literature on CSPBIs, with particular attention to the application of item response theory (IRT) and Rasch analysis in their development. METHODS: A scoping review of the literature covering the concepts of all phases of CSPBI development and evaluation was performed from MEDLINE, Embase, PsychInfo, CINAHL, and the Cochrane Library, from inception to December 30, 2022. RESULTS: The titles and abstracts of 1,967 unique references were reviewed. After retrieving and reviewing 154 full-text articles, data were extracted from 109 articles, representing 41 CSPBIs covering 21 diseases or conditions. The development of CSPBIs was conceptualized as a 15-step framework, covering four phases: 1) develop initial questionnaire items (when no suitable non-preference-based instrument exists), 2) establish the dimensional structure, 3) reduce items per dimension, 4) value and model health state utilities. Thirty-nine instruments used a type of Rasch model and two instruments used IRT models in phase 3. CONCLUSION: We present an expanded framework that outlines the development of CSPBIs, both from existing non-preference-based instruments and de novo when no suitable non-preference-based instrument exists, using IRT and Rasch analysis. For items that fit the Rasch model, developers selected one item per dimension and explored item response level reduction. This framework will guide researchers who are developing or assessing CSPBIs.

International drug price comparisons: quality assessment / Comparación internacional de precios de medicamentos: evaluación de la calidad

OBJECTIVE: To quantitatively summarize results (i.e., prices and affordability) reported from international drug price comparison studies and assess their methodological quality. METHODS: A systematic search of the most relevant databases-Medline, Embase, International Pharmaceutical Abstracts (IPA), and Scopus, from their inception to May 2009-was conducted to identify original research comparing international drug prices. International drug price information was extracted and recorded from accepted papers. Affordability was reported as drug prices adjusted for income. Study quality was assessed using six criteria: use of similar countries, use of a representative sample of drugs, selection of specific types of prices, identification of drug packaging, different weights on price indices, and the type of currency conversion used. RESULTS: Of the 1 828 studies identified, 21 were included. Only one study adequately addressed all quality issues. A large variation in study quality was observed due to the many methods used to conduct the drug price comparisons, such as different indices, economic parameters, price types, basket of drugs, and more. Thus, the quality of published studies was considered poor. Results varied across studies, but generally, higher income countries had higher drug prices. However, after adjusting drug prices for affordability, higher income countries had more affordable prices than lower income countries. CONCLUSIONS: Differences between drug prices and affordability in different countries were found. Low income countries reported less affordability of drugs, leaving room for potential problems with drug access, and consequently, a negative impact on health. The quality of the literature on this topic needs improvement.

OBJETIVO: Resumir cuantitativamente los resultados (p. ej., precios y asequibilidad) presentados en estudios de comparación internacional de precios de medicamentos y evaluar su calidad metodológica. MÉTODOS: Se llevó a cabo una búsqueda sistemática en las bases de datos más importantes -Medline, Embase, International Pharmaceutical Abstracts y Scopus, desde la fecha de inicio hasta mayo del 2009- para identificar artículos de investigación original que comparaban precios de medicamentos entre distintos países. Se obtuvo y se registró la información sobre los precios de los medicamentos de los trabajos que fueron aprobados para ser incorporados en esta revisión. Para evaluar la asequibilidad se consideró la adaptación de los precios en función de los ingresos. Se evaluó la calidad de los estudios tomando como parámetro seis criterios: el uso en países similares, el uso de una muestra representativa de medicamentos, la selección de tipos específicos de precios, la descripción del tipo de envasado, las diferentes ponderaciones aplicadas a los índices de precios y el tipo de cambio empleado. RESULTADOS: De los 1-828 estudios encontrados, se incluyeron 21. Solo un estudio cumplió adecuadamente con todos los criterios de calidad. Se observó una amplia diferencia de calidad entre los estudios a causa de los diversos métodos empleados para comparar los precios de los medicamentos, tales como, diferentes índices, parámetros económicos, tipos de precio y canasta de medicamentos. Por lo tanto, se consideró que la calidad de los estudios publicados era deficiente. Si bien los resultados de los estudios son muy diversos, en general, los medicamentos fueron más costosos en los países de ingresos más altos. Sin embargo, una vez ajustados los precios en función de la asequibilidad, se observa que los países de ingresos más altos tienen precios más asequibles que los países de bajos ingresos. CONCLUSIONES: Se encontraron diferencias en los precios de los medicamentos y la asequibilidad entre los diferentes países. En los países de ingresos bajos, se registró un grado menor de asequibilidad, lo que origina posibles problemas de acceso a los medicamentos y, en consecuencia, tiene repercusiones negativas sobre la salud. Es necesario mejorar la calidad de los estudios dedicados a este tema.