LAUSR

Background: In diagnosing subarachnoid haemorrhage (SAH), a non-contrast CT brain within 6 hours of symptom onset can yield a diagnostic sensitivity of up to 100% [1]. Cerebrospinal fluid samples can be analysed for xanthochromia if the diagnosis remains in doubt. We studied whether the test for xanthochromia was useful and cost effective in diagnosing SAH in our hospital, given that it is processed in another institution with significant associated costs. Methods: A retrospective analysis was done of all xanthochromia tests done from January 2014 to October 2016. Further data was collected from medical records of patients with ambiguous test results. Results: 206 requested tests for xanthochromia over 34 months with 178 results received. 167 (93.8%) results were negative, 10 (5.6%) ambiguous (e.g.“SAH not excluded”) and 1 (0.6%) was positive, leading to a diagnosis of SAH. None of those with ambiguous results were ultimately diagnosed with SAH. Conclusions: Xanthochromia is still a relevant test to diagnose SAH, but in a very small number of cases in our hospital. Given the proportion of positive tests (0.6%), we need to be more stringent about selecting patients who require this investigation. Xanthochromia is processed off site and costs a minimum of £106.50stg per test (€8,948 per year). We are in the process of identifying cases where the test did not add to the diagnostic process. In view of the high cost and low yield, better patient selection based on thorough history taking, decision rules such as the Ottawa Subarachnoid Haemorrhage rule, as well as timely CT scanning would cut down on unnecessary testing and result in significant savings. Reference 1. Perry JJ, Stiell IG, Sivilotti ML et al. Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study. BMJ 2011; 343: d4277.