The Value of Thoracic Computed Tomography Scans in Clinical Diagnosis: A Prospective Study

Abstract

BACKGROUND: Computed tomography (CT) scans are used extensively to investigate chest disease because of their cross-sectional perspective and superior contrast resolution compared with chest radiographs. These advantages lead to a more accurate imaging assessment of thoracic disease. The actual use and evaluation of the clinical impact of thoracic CT has not been assessed since scanners became widely available.OBJECTIVE: To identify patterns of utilization, waiting times and the impact of CT scan results on clinical diagnoses.DESIGN: A before and after survey of physicians who had ordered thoracic CT scans.SETTING: Vancouver General Hospital – a tertiary care teaching centre in Vancouver, British Columbia.SUBJECTS: Physicians who had ordered CT scans.INTERVENTION: Physicians completed a standard questionnaire before and after the CT scan result was available.MEASUREMENTS: Changes in the clinical diagnosis, estimates of the probabilities for the diagnosis both before and after the CT scan, and waiting times.RESULTS: Four hundred fifty-four thoracic CT cases had completed questionnaires, of whom 80% were outpatients. A change in diagnosis was made in 48% of cases (25% with a normal CT scan and 23% with CT scan findings that indicated a different diagnosis). The largest change in probability scores for the clinical diagnosis before and after the CT scan was 43.9% for normal scans, while it was 36.3% for a different diagnosis and 26.3% for the same diagnosis. High-priority scans were associated with decreased waiting time (−7.89 days for each unit increase in priority).CONCLUSIONS: The CT scan results were associated with a change in diagnosis in 48% of cases. Normal scans constituted 25% of the total and had the greatest impact scores. Waiting times were highly correlated with increased urgency of the presenting problem.