Elsevier

Academic Radiology

Volume 19, Issue 9, September 2012, Pages 1066-1074
Academic Radiology

Radiological alliance for health services research
Outcomes-based Assessment of a New Reference Standard for Delayed Cerebral Ischemia Related to Vasospasm in Aneurysmal Subarachnoid Hemorrhage

https://doi.org/10.1016/j.acra.2012.04.010Get rights and content

Rationale and Objectives

The purpose is to perform outcomes-based assessment of a new reference standard for delayed cerebral ischemia (DCI) related to vasospasm.

Materials and Methods

Retrospective study was performed with consecutive aneurysmal subarachnoid hemorrhage (A-SAH) patients between January 2002 and May 2009. A new reference standard for DCI was applied to the study population incorporating clinical and imaging criteria. Diagnostic accuracy was determined by chart diagnosis. Outcome measures for assessment included: permanent neurologic deficits, infarction, functional disability, treatment, and discharge status. Medical record review was performed by two blinded observers. Chi-square test calculated statistical significance between DCI and no DCI groups.

Results

A total of 137 patients were included; 59% (81/137) classified as DCI and 41% (56/137) as no DCI by the reference standard. Overall accuracy is 96% (95% confidence interval 92–99) with 100% sensitivity, 92% specificity, 94% positive and 100% negative predictive values. Patients classified as DCI had 40% (32/81) permanent neurologic deficits and 57% (46/81) infarction compared to 0% (0/56) classified as no DCI. DCI patients had 33% (27/81) functional disability compared to 13% (7/56) classified as no DCI. Ninety-four percent (76/81) DCI patients received treatment compared to 0% (0/56) classified as no DCI. DCI group had 46% (37/81) discharged to rehabilitation facilities and 11% (9/81) mortality compared to 25% (14/56) and 2% (1/56), respectively, in no DCI group. There are statistically significant differences (P < .0001) between DCI and no DCI groups for all outcome measures.

Conclusion

This new reference standard has high diagnostic accuracy for DCI related to vasospasm. The outcomes-based assessment further supports its accuracy in correctly classifying A-SAH patients.

Section snippets

Study Population

A retrospective study was performed including consecutive patients admitted to our institution with A-SAH between January 2002 and May 2009. Inclusion criterion was an admission diagnosis of A-SAH documented by noncontrast CT and/or cerebrospinal fluid analysis for SAH and CTA and/or DSA for a ruptured aneurysm. There were no exclusion criteria in this study. Institutional review board approval was obtained and written informed consent was waived.

Review of the medical records was performed for

Study Population Characteristics

A total of 137 consecutive A-SAH patients were included in the statistical analysis. Importantly, no patients were excluded from the study. Clinical and demographic characteristics of the study population are presented in Table 1.

Application of the Reference Standard Design

Applying this new reference standard to the study population, 59% (81/137) of patients were classified as DCI and 41% (56/137) as no DCI. A total of 81 patients were classified as DCI with 70% (57/81) at the primary level, 14% (11/81) at the secondary level, and 16%

Discussion

It is well-recognized that a perfect reference standard for DCI does not exist; however, the challenge remains to apply the best criteria in order to accurately classify patients in both clinical practice and research studies. DCI related to vasospasm after A-SAH is a complex entity involving delayed narrowing of the intracranial arteries that may lead to neurologic deterioration, cerebral infarction, and death. A review of the literature reveals that inconsistent terminology has been used to

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This publication was made possible by grant number 5K23NS058387-02 from the National Institute of Neurological Disorders and Stroke (NINDS), a component of the National Institutes of Health (NIH). Its contents are solely the responsibility of the authors and do not necessarily represent the official view of NINDS or NIH.

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