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.
- In 3% of cases, the aneurysm’s size needed revision of more than 1 mm. (All within 2mm.)
- Location of aneurysm was erroneously registered in 0.7% of cases. Two cases of posterior communicating aneurysms discovered on routine angiography were found to have infundibular dilation and were deleted from the study.
- In 3.4% of cases, there are defective data of family history and past medical history.
- Follow-up modified Rankin scale was recorded incorrectly more than or equal to 2points in 1% of cases.
Above listed points were corrected in each institution.
These errors did not influence the results of the statistical analysis of the data.