RESEARCH METHODOLOGY - CODING PERCEIVED MORBIDITY IN GENERAL-PRACTICE- AN EVALUATION OF THE READ CLASSIFICATION AND THE INTERNATIONAL CLASSIFICATION OF PRIMARY-CARE (ICPC)

Objectives - To evaluate the Read Classification and the International Classification of Primary Care (ICPC). Methods - The Read Classificat ion was used to code the diagnoses for 3474 patient encounters, in a p ilot sample of three volunteer practices (11 general practitioners), a nd the ICPC was used to code 21,416 patient encounters in a stratified quota sample of 22 practices (59 general practitioners), in a survey aiming to relate prescribing to perceived diagnosis. Results/Experienc e - The Read Classification was found to be a detailed and exhaustive classification of medical diagnoses, but it was more time consuming to use than the ICPC, due to the complexity of the classification, the o ver-use of alpha characters compared to the ICPC, and the mixing of al pha characters with numeric digits within the codes. Encoding, decodin g and statistical analysis were found to be more straightforward using the ICPC compared with the Read Classification. The ICPC was found to be deficient in 40 important diagnoses, and these are listed. Conclus ion - The Read Classification was of limited value in this drug utiliz ation survey, in that the design of the code reduced its utility in st atistical analyses. The ICPC was an efficient code, which met the crit eria of exclusiveness, usefulness and hierarchy. The classification is not exhaustive enough to prevent loss of information as a result of c oding, but the authors' amendments virtually eliminated this problem. (C) 1997 John Wiley & Sons, Ltd.