Predictive value of signs and symptoms in the diagnosis of subarachnoid hemorrhage among stroke patients

Clinical diagnosis of subarachnoid hemorrhage (SAH) is frequently misdiagnosed with intracerebral hemorrhage (ICH) or cerebral infarction (CI), which delays appropriate referral. This study was undertaken to create a clinical index to select, among stroke patients, those with the highest probability of having a SAH. Clinical data of patients with acute stroke were evaluated with the X(2) and the Fisher exact test; a p value <0.05 was considered significant. Significant variables were included in a ''log-lineal regression analysis'' where those with an odds ratio (OR) 95% confidence limits not including the unit were considered to construct an index using the odds ratio coefficient (C). The results indicated that of 197 records which were included, 22 cases of SAH and 175 of ICH or CI were demonstrated. Kappa coefficients for observer variation in clinical data retrieval was 0.91. After ''log-lineal regression analysis'' was carried out the following variables were significant: neck stiffness (C=3, OR=21); lack of focal neurologic signs (C=2, OR=6.88); and age less than or equal to 60 years (C=1.5, OR=4.35). A fourth variable, seizures (C=1, OR=3.25), was marginally significant (p=0.07), but added predictive value to the index. The positive predictive values of the sum of the coefficients were: 0=0%; 1-2=3%; 2.5-3.5=21%; 45=40%; 6.5=75%; 7.5=100%. In conclusion, when a stroke patient shows neck stiffness, or any combination of young age, lack of focal neurologic signs or seizures (a score greater than or equal to 2.5, the index has a 91% sensitivity and 82% specificity), he/she must be referred to a tertiary care center.