Study design and outcome measures in studies on aneurysmal subarachnoid hemorrhage

Methods of performing and reporting randomized clinical trials (RCTs) are available, but weaknesses still occur. For observational studies, methodology is less well described, and weaknesses are even more likely. In recent guidelines for patients with subarachnoid hemorrhage (SAH), 25% of treatment recommendations are based on clinical trials. To interpret the results of research on the therapeutic effect of treatment modalities, definition of outcome measures is essential. We assessed quality of study design and outcome measures and presence and precision of definitions concerning major complications of SAH in studies evaluating treatment strategies in patients with aneurysmal SAH.

We retrieved and reviewed all articles on treatment strategies in patients with SAH that fulfilled a prespecified set of criteria and were published during 1990-1999 in 10 general, neurosurgical, or neurological journals. We categorized articles into RCTs, observational studies with a control group, and observational studies without a control group. We assessed study design by means of a prespecified set of methodological criteria. For outcome measures we assessed whether a prespecified outcome measurement was defined and whether any handicap scale was used. For complications after SAH we assessed whether the definition included a description of the clinical features and a technical investigation with criteria for abnormal results.

We identified 18 RCTs, 24 observational studies with a control group, and 41 uncontrolled observational studies. Two RCTs, no observational studies with a control group, and 15 observational studies without a control group met all criteria for study design. A primary outcome measure was specified in 67 of the 83 studies and was defined in 59. Any measure of handicap or information on degree of dependence was given in 65 of 83 studies. A complete definition of delayed cerebral ischemia was given in 13 of 66 studies, of rebleeding in 2 of 26 studies, and of hydrocephalus in 2 of 14 studies.

Most studies on treatment strategies in SAH suffer from methodological weaknesses. This implies that current management of patients with SAH is based on weak evidence.