Validation of the Essen Stroke Risk Score and the Stroke Prognosis Instrument II in Chinese Patients
Background and Purpose—Little was known about the predictive accuracy of the Essen Stroke Risk Score and the Stroke Prognostic Instrument II in Chinese patients with stroke.
Methods—We evaluated the predictive accuracy of both Essen Stroke Risk Score and Stroke Prognostic Instrument II scores for both recurrent stroke and combined vascular events using data from a prospective cohort of 11 384 patients with acute ischemic stroke and transient ischemic attack admitted to 132 urban hospitals throughout China.
Results—The cumulative 1-year event rates were 16% (95% CI, 15%–16%) for recurrent stroke and 18% (95% CI, 18%–19%) for combined vascular events. Both event rates were significantly higher in patients with transient ischemic attack and increased significantly from lower to higher Essen Stroke Risk Score and Stroke Prognostic Instrument II categories. Essen Stroke Risk Score and Stroke Prognostic Instrument II had similar predictive accuracies for each study outcome.
Conclusions—In Chinese patients with ischemic stroke or transient ischemic attack, both Essen Stroke Risk Score and Stroke Prognostic Instrument II scores are equally able to stratify the risk of recurrent stroke and combined vascular events.
Recurrent stroke and subsequent cardiac events after stroke are major contributors to disability and mortality for stroke victims.1 Identification of those patients at high risk of recurrent stroke and/or cardiac events is critically important for both inpatient management and outpatient care. Several predictive scores have been developed to help stratify the risk of recurrent stroke and/or cardiac events for patients with transient ischemic attack (TIA) and ischemic stroke, including the Essen Stroke Risk Score (ESRS) and the Stroke Prognostic Instrument II (SPI-II) score. Although both ESRS and SPI-II have been validated in Western populations,2,3 the performance of these scores has not been examined in large Chinese stroke patient populations.
Data for patients with TIA or ischemic stroke from the China National Stroke Registry (CNSR) were used in this report. The design, rationale, and baseline information of CNSR has been described previously.4 In brief, CNSR was a nationwide prospective hospital-based cohort study of consecutive patients with stroke aged ≥18 years admitted to 132 hospitals within 14 days after the onset of symptoms between September 2007 and August 2008 in China. Stroke and TIA were defined based on World Health Organization criteria.5 Except for TIA, all the diagnoses were confirmed by brain CT or MRI. Detailed baseline data were abstracted prospectively using paper-based registry forms. Patients or their authorized proxies were contacted by telephone 3, 6, and 12 months after symptom onset. The study was approved by the central Institutional Review Board at Beijing Tiantan Hospital. Written informed consent was obtained from the patient or his or her legally authorized representative.
The study outcomes were recurrent stroke and combined vascular event. A recurrent stroke was defined as a newly diagnosed stroke in a patient in whom the initial symptoms had substantially or fully recovered. A combined vascular event was defined as any event including recurrent stroke, myocardial infarction, or cardiovascular death.
Proportions were used for categorical variables; mean with SD were used for continuous/score variables. Chi-square tests were used to compare categorical variables; Student t test was used for continuous/score variables. The cumulative event rates and the corresponding 95% CIs of outcomes were calculated based on a binomial distribution. We estimated the discrimination of ESRS and SPI-II to predict 1-year cumulative recurrent stroke and combined vascular event using the area under the curve by c-statistic. We used 1000 bootstrap samples to estimate the 95% CI for each c-statistic. All tests were 2-tailed, and P<0.05 was considered statistically significant. All analyses were conducted using SAS 9.1.
There were 11 384 eligible patients with TIA (1061) or ischemic stroke (10 323) in our analysis, after excluding 1381 (10.5%) patients with a history of atrial fibrillation and 851 (7.0%) patients without follow-up. The patients with and without complete follow-up were comparable in terms of the prevalence of baseline risk factors and clinical characteristics (Supplemental Table; http://stroke.ahajournals.org).
The cumulative 1-year event rates were 16% (95% CI, 15%–16%) for recurrent stroke and 18% (95% CI, 18%–19%) for combined vascular event. Both event rates were significantly higher in TIA, especially for patients in lower ESRS and SPI-II score categories compared with patients with ischemic stroke. In addition, both event rates increased significantly for patients from lower to higher ESRS and SPI-II score categories (Table 1).
ESRS and SPI-II scores had similar predictive accuracy for either recurrent stroke or cumulative vascular events, and there were no statistically significant differences in area under the curve values for each outcome using either ESRS or SPI-II score (Table 2).
Our results showed that both ESRS and SPI-II scores were equally able to stratify the risk of recurrent stroke and combined vascular events in a Chinese stroke population and the area under the curve values were similar to a recent study in German patients with stroke.2 These scores may help the clinicians to identify the patients at high risk of recurrent stroke and/or cardiac events and raise the awareness of managing risk factors for both inpatient treatment and outpatient care. However, the relatively low accuracy may raise concerns for the usefulness of these 2 predictive scores in individual treatment decisions and secondary prevention.
There were limitations in this study. The study sites were selected from urban areas and may represent the institutes having better inpatient and outpatient care; the rates for recurrent stroke and cardiac events may be underestimated. In addition, some of the cardiovascular deaths may be misdiagnosed. Because the analysis was performed only in patients who completed the 1-year follow-up, there may be potential biases in estimation of event rates and calculation of prediction accuracies.
Sources of Funding
This study was funded by the Ministry of Science and Technology and the Ministry of Health of the People's Republic of China (grant no. 2008ZX09312-008 and 2009CB521905).
The online-only Data Supplement is available at http://stroke.ahajournals.org/lookup/suppl/doi:10.1161/STROKEAHA.111.624148/-/DC1.
- Received April 25, 2011.
- Revision received June 29, 2011.
- Accepted July 19, 2011.
- © 2011 American Heart Association, Inc.
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