Present-at-admission diagnoses improve mortality risk adjustment and allow more accurate assessment of the relationship between volume of lung cancer operations and mortality risk

Background. Mortality risk adjustment is a key component of studies that examine the statistical relationship between hospital lung cancer operation volume and in-hospital mortality. Previous studies of this relationship have used different methods of adjusting for factors that influence mortality risk, but none have adjusted for differences in comorbid disease using only diagnoses identified as present-at-admission. Methods. This study uses adjustments for conditions identified as present-at-admission to examine, the statistical relationship between the volume of lung cancer operations and mortality among 14,456 Californiia hospital patients, and compares these results to other methods of risk adjustment similar to those used in previous studies. Results. Mortality risk adjustment using present-at-admission diagnoses yielded better discrimination and explained more of the variability in observed deaths. Large increases in hospital procedure volume were associated with much smaller decreases in mortality risk than those estimated using comparable risk adjustment models. Conclusions. Present-at-admission diagnoses can be used to improve mortality risk adjustment and may allow a more accurate assessment of the relationship between Procedure volume and mortality risk.