The International Cooperative Study on the Timing of Aneurysm Surgery
The International Cooperative Study on the Timing of Aneurysm Surgery evaluated the results of surgical and medical management in 3521 patients between December, 1980, and July, 1983. At admission, 75% of patients were in good neurological condition and surgery was performed in 83%. At the 6-month evaluation, 26% of the patients had died and 58% exhibited a complete recovery. Vasospasm and rebleeding were the leading causes of morbidity and mortality in addition to the initial bleed. Predictors for mortality included the patient's decreased level of consciousness and increased age, thickness of the subarachnoid hemorrhage clot on computerized tomography, elevated blood pressure, preexisting medical illnesses, and basilar aneurysms. The results presented here document the status of management in the 1980's 1).
Olijnyk et al. reviewed the International Cooperative Study on the Timing of Aneurysm Surgery (ICSTAS), a landmark observational study on the management of ruptured aneurysm patients. They discussed the impact of the ICSTAS lesson on the interpretation of future observational studies using Big Data.
Per-protocol (or as-treated) analyses can be misleading: The ICSTAS study provided 'as-treated' results clearly in favour of delayed surgery, while overall management or ITT results showed no difference between early and delayed surgery. A contemporary RCT showed that early surgery was best. ICSTAS' lesson is that observational studies can provide misleading results when intent-to-treat categories are not predefined in the first place.
Intent-to treat analyses are the most appropriate way to analyze data, whether from randomized trials or observational studies. This observation has momentous consequences. A science of medical practice is impossible without predefined questions regarding optimal care 2).