Interobserver variability in the interpretation of computed tomography following aneurysmal subarachnoid hemorrhage

Clinical article

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Object

Numerous abnormal findings may be evident on CT scans after aneurysmal subarachnoid hemorrhage (SAH). Here, the authors assess the interobserver variability in the radiological interpretation of the initial CT scan following SAH.

Methods

Two experienced reviewers, a neurosurgeon and a neuroradiologist, independently prospectively reviewed the initial CT scans of 413 patients enrolled in the CONSCIOUS-1 trial. Measured variables included SAH, intraventricular hemorrhage, intracerebral hemorrhage, subdural hematoma, chronic infarction, midline shift, and hydrocephalus. To assess interobserver variability, weighted kappa values and intraclass correlation coefficients (ICCs) were calculated and Bland-Altman analysis was performed.

Results

Moderate to substantial agreement was found for most of the CT scanning findings. There was fair to moderate interobserver agreement between reviewers when determining the extent of SAH based on a descriptive categorical classification (kappa 0.41; 95% CI 0.33–0.49), and better agreement when a semiquantitative scale was used (ICC 0.56; 95% CI 0.49–0.62). There was poor agreement between reviewers for the presence of hydrocephalus (kappa 0.34; 95% CI 0.20–0.48), but substantial to near perfect agreement on ventriculocranial ratio measurements (ICC 0.77; 95% CI 0.72–0.81).

Conclusions

The authors' findings suggest that there is considerable interobserver variability in the interpretation of CT scans after SAH. Quantitative measures may reduce interobserver variability in comparison with qualitative or categorical scales. Variability in interpretation of CT scans has implications for patient care and conduct of clinical trials. It may be beneficial to develop standardized assessments to ensure consistent evaluation of measured variables.

Abbreviations used in this paper: EDH = epidural hematoma; ICC = intraclass correlation coefficient; ICH = intracerebral hemorrhage; IVH = intraventricular hemorrhage; SAH = subarachnoid hemorrhage; SDH = subdural hematoma; VCR = ventriculocranial ratio.

Article Information

Address correspondence to: R. Loch Macdonald, M.D., Ph.D., St. Michael's Hospital, 30 Bond Street, Toronto, Ontario M5B 1W8, Canada. email: MacdonaldLo@smh.ca.

Please include this information when citing this paper: published online August 5, 2011; DOI: 10.3171/2011.7.JNS11725.

© AANS, except where prohibited by US copyright law.

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Figures

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    A: Scatter diagram of Hijdra score for 2 reviewers in 413 patients. B: Bland-Altman plot of interobserver variability in interpretation of subarachnoid clot burden using the Hijdra score. Upper and lower bars represent 95% limits of agreement, and the center bar represents the mean. C and D: Scatter diagram (C) and Bland-Altman analysis (D) for intraventricular clot burden measured using the modified Graeb score. E and F: Scatter diagram (E) and Bland-Altman analysis (F) for hydrocephalus measured using the VCR.

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