High positive computed tomography yields in the emergency department might not be a positive finding

There is growing pressure to reduce unnecessary computed tomography (CT) imaging requests that the radiology department receives from the emergency department (ED); however, information on acceptable usage rates and diagnostic yields remains scanty.

To describe the indications, clinical categories and positive yield rates of patients receiving CT scans in the ED.

A retrospective record review was done of all patients who received CT scans at an urban, adult academic ED during a 4-month period. Primary outcomes were to establish CT scan usage and positive yield rates. Other outcomes included analysis of indications, demographics and anatomical areas scanned.

Scans (n=1 010) were analysed. The median age of patients was 36 (range 4 - 93) years. Male patients received 64.3% of all scans, as well as 75.7% of the scans performed for trauma. The majority of the scans were for trauma patients. However, non-trauma patients had a higher positive yield; the non-trauma positive yield rate was 61.8% compared with the trauma positive yield rate of 47.1% (p<0.001). The majority of scans performed were of the head (58%) and neck (20%), with lowest positive yield rates of 48.9% and 17%, respectively. The overall CT scan usage rate was 4.6% and overall positive rate 53.8%.

A negative CT scan does not necessarily mean that the test was not indicated. Higher positive yield rates may reflect insufficient use of CT scanning by the ED. Local guidelines should be established to ensure judicious and effective clinical use of CT scans.