A subarachnoid haemorrhage-specific outcome tool.

Functional outcome after subarachnoid haemorrhage has traditionally been assessed using scales developed for other neurological conditions. The modified Rankin score and Glasgow Outcome Scale are most commonly used. Employment of these scales in subarachnoid haemorrhage is hampered by well recognized limitations. We set out to develop and validate a new condition-specific subarachnoid haemorrhage outcome tool (SAHOT). Items addressing diverse aspects of the impact of subarachnoid haemorrhage were collected during focus groups involving patients, next-of-kin and multidisciplinary professionals involved in subarachnoid haemorrhage management. After a series of iterative revisions, the resultant questionnaire was applied to patients and their next-of-kin at 1, 3 and 6 months post-subarachnoid haemorrhage. Rasch methodology was used to finalize the structure of the questionnaire and explore the extent to which SAHOT scores met Rasch-based criteria of successful measurement. The SAHOT was further assessed using traditional scale evaluation techniques, and validated in a second separate subarachnoid haemorrhage patient cohort. The final SAHOT included 56 items dealing with cognitive, physical, and behavioural/psychological consequences of subarachnoid haemorrhage. Rasch analysis indicated the scale successfully measured functional outcome post-subarachnoid haemorrhage. Three item scoring categories produced the best scale performance. There was no evidence of differential item functioning between patients and next-of-kin. The SAHOT was found to be acceptable, have good convergent and divergent validity, good discrimination and excellent responsiveness. It was successfully validated in a second subarachnoid haemorrhage patient cohort. The SAHOT offers the first subarachnoid haemorrhage-specific scientifically robust outcome measure with potential utility in neurovascular clinical services and research studies.