The efficacy of intravenous iodinated contrast media in the diagnostic accuracy of cranial computed tomography (CT) in patients with a possible missed diagnosis at Dr George Mukhari Hospital, Pretoria

Abstract

Objective: The objective was to determine the incidence of missed pathology on normal non contrast enhanced cranial computed tomography (NECT).Method: Records of cranial computed tomography scans done over a 12 month period at the Dr George Mukhari Hospital were evaluated by three readers. The NECT and contrast enhanced cranial computed tomography (CECT) were read at separate occasions and readers did not have access to a history, each other’s interpretation or to their own interpretation of the NECT when the CECT was evaluated. The data was evaluated and analysed after the 3 readers had seen the cases individually. Interpretation discrepancies were resolved during a meeting between all 3 readers and consensus was reached. Cases with missed pathology on the NECT were evaluated retrospectively at a joint meeting between the 3 readers to determine whether the pathology was visible on the NECT and thus to determine the combined reader error rate. Results: In this study 3.28 % of cases had pathology missed by 3 readers on the NECT. Retrospective viewing reduced this to 1.42% indicating a reader error of 1.85%. This incidence of missed pathology correlates with the most recent studies done. Having a thorough medical history of the patient and selecting those with clinical findings indicating the need for a CECT will reduce the incidence of missed pathology.Conclusion: Patients with a normal NECT and no fever, meningism, confusion, focal/lateralizing signs, a history of tuberculosis or tumours, or risk factors for dural venous sinus thrombosis have a very small chance of missed pathology on NECT. The risk of contrast induced adverse events outweighs the risk of missing pathology on a normal NECT provided there is no clinical indication necessitating a CECT. Omitting unnecessary CECT will in turn reduce the risk of intravenous iodinated contrast and the radiation exposure to the patient. These two factors will ultimately reduce the running cost of the CT department and increase the throughput of patients. Alternatively omitting the NECT will reduce the radiation exposure to the patient.Reporting errors can be reduced by assessing and managing risk factors in each department i.e. viewing conditions and workload.