Reliability of report coding of hospital referrals in primary care versus practice-based coding

Coding of medical data according to a suitable classification is useful to epidemiological research in primary care but its implementation at practice -based level may be considered as extra work by participating practitioners . Secondary coding from reported data can be considered as a possible alter native to practice-based coding. The purpose of this study was to assess th e inter-rater reliability of report coding versus practice-based coding of morbidity data. Via teleinformatics, 300 French general practitioners from the French Sentinel epidemiological network transmitted in free text, on a continuous real-time basis, the health problems generating each hospital re ferral they made since August 1997. All these reports were centrally coded according to the International Classification of Primary Care (ICPC). A sub sample of 120 reports were coded in local practices for comparison. Codes r esulting from blind centralized free-text coding were compared with practic e-based codes. For the 120 referrals reported, the kappa measure of agreeme nt for the number of codes was 0.65 (95% confidence interval [CI], CI: 0.52 -0.77), and for the chapters selected, 0.84 (95% CI: 0.78-0.91). Discrepanc ies attributable to the centralized coding only occurred for 7.5% of the re ferrals, and were due to the lack of specificity of the information transmi tted as free text. A thesaurus of correspondences between problem(s) genera ting referrals and ICPC codes was built from 5000 referrals, and has been u sed routinely for the automated report coding of an additional sample of 16 91 referrals. We conclude that centralized coding is a reliable alternative to practice-based coding in primary care, provided that physicians give su fficiently specific information.