The NSW Pathology Atlas of Variation: Part I - identifying emergency departments with outlying laboratory test–ordering practices

Study objective: Abdominal pain and chest pain are leading reasons for emergency department (ED) presentations, with laboratory tests frequently ordered to aid the diagnostic process. Our study aims to identify EDs with outlying laboratory ordering practices for patients presenting with undifferentiated abdominal pain and chest pain. Methods: This was a retrospective observational study of 519,597 patients who presented with the complaint of abdominal or chest pain at 44 major hospital EDs across New South Wales, Australia, from January 2017 to September 2018. For each condition, we evaluated the risk-adjusted rate of ordering at least 1 laboratory test and of each of the top 15 ordered tests. We used funnel plots to graph variations in test ordering and identify EDs with outlying test-ordering practices. EDs lying above or below the 99.8% funnel control limits were regarded as outliers. Results: From 3,360,152 unplanned presentations, abdominal pain and chest pain represented 8.8% (n=296,809) and 6.6% (n=222,788) of all cases, respectively. No major outliers were observed for ordering at least one laboratory test; however, variations were observed for individual tests. For abdominal pain, the top 3 tests with the highest ordering variation included glucose (20 outlier EDs), C-reactive protein (10 outliers), and calcium-magnesium-phosphate (7 outliers). For chest pain, the top 3 tests with the highest ordering variation were glucose (21 outlier EDs), C-reactive protein (17 outliers), and liver function test (14 outliers). Conclusion: Identifying EDs with outlying laboratory-ordering practices is the first step in initiating context-specific evaluation of whether outlying variations are unwarranted.