Residual coding in ICHPPC: the size of the problem and its impact on research.

In initial field trials of the International Classification of Health Problems in Primary Care (ICHPPC), the number of problems coded in residual (;other') categories was <5 per cent. Since then, there have been no published analyses of the residual category. Problems have been coded and computerized for over eight years at the Medical University of South Carolina Department of Family Medicine model practice. An analysis of that experience demonstrates that 14.3 per cent of the 85,000 problems were coded as residuals. Many classes or subclasses had >40 per cent coded as residuals. A residual as large as this is a major deterrent for research or practice analysis in a residency setting in anything more than a general category or descriptive manner. If many residuals also occur in other settings, this aspect of the code as well as the coding itself will need further study and improvement.