1. Comparing the Use of Diagnostic Tests in Canadian and US Hospitals Steven J Katz, Laurence F McMahon and Willard G Manning Medical Care. 34(2):117-125, February 1996

2. Primary question : Hospital expenditures per capita are 1/3 higher in the US than in Canada, But total hospital days per capita in the US are much lower. Why?

3. Possible reasons: Hospital resource prices may be higher in the US (e.g. employee wages) US hospitals may use more resources to provide clinical services (e.g. higher investment in technology in the US) Comparable patients may receive more clinical services in US hospitals

4. Previous research: Hospital employee wages appear similar between countries (Haber et al, 1992) Administrative costs and the cost of maintaining higher capacity of technology much greater in the US (Redelmeier and Fuchs, 1993, Himmelstein and Woolhandler, 1986, and Danzon, 1992) However, past studies on differences in volume of clinical services provided to inpatients have produced inconsistent results.

5. Purpose of this paper: To examine international differences in the level of diagnostic services provided to inpatients by comparing utilization of radiology and laboratory tests received by a selection of inpatients admitted to eight hospitals in Canada and the US.

6. Methods - Hospital Selection: Two university hospitals and two large community hospitals were selected in each country with comparable numbers of inpatient days and inpatient beds In 1991: –US university hospitals: 511,406 inpatient days, 1566 beds –Canadian university hospitals: 431,822 inpatient days, 1743 beds –US community hospitals: 281,496 inpatient days, 1121 beds –Canadian community hospitals: 287,845 inpatient days, 1020 beds Each hospital also had in-hospital availability of advanced diagnostic services such as CT, MRI, nuclear medicine and ultrasound.

7. Methods - Patient Selection: Patients with selected primary diagnoses that were frequent sources of admission in both countries were included in the study. The diagnoses were: –Medical: cerebral vascular accidents (DRG 14), pneumonia (DRG 89, 90), myocardial infarction (DRG 121, 122) –Surgical: appendectomy (DRG 167), hip fracture (DRG 210), major joint procedures (DRG 209) and hysterectomy (DRG 358, 359) Patients with hospital stays longer than DRG Medicare outlier threshold were excluded to minimize differences in patient population between countries.

9. Methods – Measuring Utilization: All radiology, hematology and biochemistry tests were obtained for patients discharged with selected diagnoses during 1990 and 1991 from computerized databases from each hospital. Tests were aggregated into clinical categories: –radiology: radiographs, CT/MRI, ultrasound, nuclear medicine, vascular studies –laboratory: hematology, basic biochemistry, advanced biochemistry

10. Methods – Measuring Utilization: Each test was assigned a relative value unit (RVU) based on measured differences in relative cost for the direct cost of performing test. RVUs were summed by clinical category for each patient, then mean RVUs were compared between countries by category for medical and surgical patients adjusting for age, gender, DRG and university status Radiology tests were weighted based on technical component of the Medicare Resource Based Relative Value Scale. Laboratory tests were weighted using cost-to-charge ratios calculated by the U of M finance department.

11. Analysis: Radiology use modeled in two parts: –Logistic function used to model probability of having any test since 7% of medicine patients did not receive any radiology test –OLS regression using natural log transformation to model utilization among those who did have tests Laboratory tests modeled using OLS regression on log (RVU) to calculate adjusted means Covariates used in both models: –Four linear age splines (20,40,60,80) –Gender, DRG, University hospital status –Country/Age and Country/DRG interactions

13. Conclusions: Comparable patients admitted to US hospitals received more diagnostic tests than their Canadian counterparts These differences were mostly due to: –higher use of radiology by medical patients in the US –greater use of high-cost testing, especially in elderly population, in US hospitals

14. Comments: Cannot generalize these results, since not all hospitals in Canada are likely to have same availability of high- tech equipment as US hospitals RVUs for procedures in Canada may actually be different from the US standards used in this study