Misclassification problems in diagnosis-related groups. Cystic fibrosis as an example

Under the Medicare prospective payment system, which is based on diagnosis-related groups, patients with certain diseases may be inappropriately classified. To study this problem using cystic fibrosis as an example, we examined discharge-abstract data from 14 cystic fibrosis centers in a comparison of resource-use requirements by patients with cystic fibrosis and other patients in the same diagnosis-related group. There were 1763 patients with cystic fibrosis and 25,628 other patients in the 87 diagnosis-related groups that contained at least one patient with cystic fibrosis. For the eight diagnosis-related groups in which patients with cystic fibrosis were classified most often, the average length of stay of patients with cystic fibrosis was 14.9 days, as compared with an average of 8.3 days for the other patients (P less than 0.001). For three hospitals, we were able to convert charges to costs. The average cost of treating patients with cystic fibrosis was $7,262, as compared with $2,908 for all other patients in the same diagnosis-related group (P less than 0.001). The ratio between the costs of treating patients with cystic fibrosis and other patients (2.5) was greater than the ratio between the lengths of stay for the two groups (1.8), reflecting the more intense use of resources by the patients with cystic fibrosis. A possible solution to the problem of misclassification is to define one or more new diagnosis-related groups for cases of cystic fibrosis or determine a new location within the diagnosis-related group system so that patients with cystic fibrosis can be classified with patients who use similar amounts of resources.