Retrospective analysis of evidence base for tests used in diagnosis and monitoring of disease in respiratory medicine

OBJECTIVES: To determine how many common clinical tests used in a respiratory medicine outpatient clinic are based on high quality evidence. DESIGN: Retrospective review of case notes. Record of first three tests for each patient. Diagnostic tests, tests used to assess existing condition, explicit trials of therapy were included. Literature search for supporting evidence and grading of best evidence for each test. SETTING: Inner city university teaching hospital in the United Kingdom. PARTICIPANTS: All new outpatients referred to a single respiratory medicine team over a period of three months. MAIN OUTCOME MEASURES: Proportion of tests supported by level 1a-1c evidence (scale developed by Centre for Evidence Based Medicine). RESULTS: Only half the tests that were used to make or exclude a diagnosis and a fifth of the tests used to assess a known condition were supported by level 1a-1c evidence. There was no evidence to support trials of therapy. CONCLUSIONS: A large proportion of clinical tests in respiratory medicine are not supported by level 1a-1c evidence. None of the therapeutic trials that were used were supported by evidence.