Laboratory Test Utilization and Repeat Testing for Inpatients of Age 80 and Over in Australia: A Retrospective Observational Study

Abstract

Abstract Introduction Repeat laboratory testing is often necessary in hospitals. However, frequent blood draws can be harmful to older patients. The objective of this study was to identify the most frequently ordered laboratory tests and repeat testing rates for these tests among older inpatients. Methods A retrospective observational study of inpatients of age 80 years and over in 4 public hospitals in New South Wales, Australia, was conducted between 2008 and 2013. Proportions of laboratory tests and proportions of repeated tests among the most frequently used tests were reported. Results There were 42739 patients with 108003 admissions (56.2% women; 43.2% of ages 80–84). Of these admissions, 95.9% had a laboratory test, with 3012577 tests recorded. Five tests accounted for 62% of all tests and were present in 98.5% of admissions: electrolytes urea and creatinine (EUC; 18% of all tests ordered), complete blood count (CBC; 16.7%), calcium magnesium phosphate (CaMgPhos; 10.2%), liver function test (LFT; 9.0%), and C-reactive protein (CRP; 8.0%). Proportions of repeat tests for this group performed outside recommended minimum repeat intervals were 10.3% EUC, 8.9% CBC, 41.5% CRP, 68.2% CaMgPhos, and 65.2% LFT tests. An exponential increase in repeat testing for all 5 tests was observed around 24 h after a previous test. Conclusion Compliance with guidelines on repeat testing intervals among older patients is variable. A better understanding of the underlying reasons for repeat testing would allow targeting of interventions, including decision support, to improve laboratory use for older inpatients.