Comparability and validity of two clinical scores in the early differential diagnosis of acute stroke

Abstract

Objective: To compare two available clinical scores for the differential diagnosis of cerebral ischaemia and haemorrhage in acute stroke patients. Design: Prospective, multicentre study of acute stroke patients evaluated with computed tomography and Allen and Siriraj scores; the scores were tested for comparability (kappa statistic) and validity (sensitivity, specificity, positive and negative predictive values, diagnostic gain). The effect of a policy of using Allen and Siriraj scores to determine pathological type of stroke before computed tomography was calculated. Setting: Three hospitals in Italy, all participating in the international stroke trial, with different access facilities to computed tomography. Subjects: 231 consecutive patients who were screened in the three hospitals for possible inclusion in the international stroke trial from 1 November 1991 to 31 May 1993. Results: The prevalence of haemorrhage (diagnosed with computed tomography) was 14.7% (95% confidence interval 10.1% to 19.3%). Allen scores were “uncertain” in 44 cases and Siriraj scores in 38 cases; in the 164 cases with both the scores in the range of “certainty” kappa was 0.72. Sensitivity, specificity, positive and negative predictive values, and diagnostic gain for haemorrhage were 0.38, 0.98, 0.71, 0.91, and 0.58 for Allen scores and 0.61, 0.94, 0.63, 0.93, and 0.48 for Siriraj scores; positive predictive values for infarction were 91% for Allen scores and 93% for Siriraj scores. According to these data, of 1000 patients with acute stroke, 680 would be correctly and 70 wrongly diagnosed as “ischaemic” with the Allen score; the figures would be 671 and 48 with Siriraj score. Conclusion: When computed tomography is not immediately available and the clinician wishes to start antithrombotic treatment (or randomise patients in a clinical trial), the Siriraj score (and possibly the Allen score) can be useful to identify patients at low risk of intracerebral haemorrhage.