Age and laboratory costs for hospitalized medical patients.

Objective: To examine the hypothesis that older hospitalized patients have higher laboratory costs than younger patients in the same severity-adjusted diagnosis-related group (DRG).

Design: We obtained hospital case mix data sets (1995-1997) from the Massachusetts Division of Health Care Finance and Policy. We selected discharge abstracts from 4 medical DRGs, at 5 large academic hospitals (n = 15,265) and 5 midsized community hospitals (n = 10,540), for analysis. We converted laboratory and blood product charges to direct costs using the department-specific ratio of cost to charges. We adjusted diagnostic groups for severity of comorbid conditions and complications using the refined DRG method.

Main Outcome Measures: Hospital length of stay (LOS), laboratory direct cost (LDC) per hospitalization, LDC per hospital day, and ratio of LDC to total direct cost.

Results: Hospital LOS was longer for older patients in all comparisons. Laboratory direct cost per hospitalization was higher for older patients in some DRGs, but lower in other DRGs. Laboratory direct cost per hospital day was almost always less for older patients than for younger patients, both at academic and community hospitals. Data stratification by gender, admission status, and principal diagnosis yielded substantially the same pattern of cost differences observed within the larger data set.

Conclusions: Older medical patients have longer hospital stays and generally higher costs. These patients also have a significantly decreased rate of laboratory resource consumption over the course of hospitalization (LDC per hospital day), as well as lower laboratory costs as a proportion of total costs. Age-specific differences in LOS and cost parameters were essentially unchanged after controlling for several potential sources of bias.