Meningococcal vaccine coverage in Hajj pilgrims
1343 identifying haemorrhagic stroke; and (d) its use in the emergency setting should be assessed on the basis of pretest probability. The latter deserves a few additional remarks. The proportion of patients with a defi nite stroke seen by Chalela and colleagues (61% is much lower than that reported from comparable settings, 2,3 where emergency department physicians correctly identifi ed 89 91% of acute stroke patients before doing brain imaging. A high pretest probability is likely to off set the expected advantage of MRI over CT. 4 Moreover, CT is as helpful as MRI in identifying bleeding, which cannot be clinically detected. Therefore, when a patient's referral for brain imaging is based on a good quality clinical examination, MRI is no better than a standard CT scan. In our post evaluation survey, all participants agreed that MRI should replace CT if a low pretest probability of acute stroke (eg, 60 70% is expected. Students who assessed the paper were:
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