Source document verification

During the study period of UCAS Japan between 2001 and 2010, the hospital records and images of 956 patients from a random sample of 21 institutions were documented by outside investigators.

The results of analysis showed that document errors were minimal.

1. In 3% of cases, the aneurysm’s size needed revision of more than 1 mm.
2. Two cases of posterior communicating aneurysms discovered on routine angiography were found to have infundibular dilation and were deleted from the study.

These errors did not influence the results of the statistical analysis of the data.

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Copyright (c) Unruptured Aneurysm Study of Japan, Japan Neurosurgical Society