Background: For over 20 years, researchers wanting to record, discuss and compare drug-related problems (DRPs) have had the task of choosing between a multiplicity of classification systems offering a variable number of categories identified as causes of DRPs and DRPs.
Objective: To characterise studies which have reported DRPs through the use of a DRP classification system to determine types of classification systems chosen, factors influencing their choice, and methodological issues that may have affected their application.
Method: A systematic search of MEDLINE, CINAHL, International Pharmaceutical Abstracts (Ovid), EMBASE and PubMed was performed. All English language studies reporting DRPs through the use of a classification system published between January 2000 and July 2013 were reviewed, with no limitation on the type of study.
Results: Of 2,774 articles screened, 268 met our inclusion criteria. We identified the use of 20 different types of DRP classification systems. Three quarters of studies modified an existing classification system or developed their own. Few studies stated reasons for choice of system. We identified issues such as variability in skills of data collectors, selective choice of patients and missing data, affecting application of classification systems and limiting quality, analysis and comparison of studies.
Conclusion: There appeared to be no consensus on preference or structure of classification systems. Future studies should consider addressing or acknowledging the methodological issues identified. Through identification and discussion of these problems, recommendations for future studies and for practice have been made.