Do Researchers Consider the Inter-relationship Between Time to Assessment and Admission Severity in Acute Stroke?

Background

Stroke severity, often quantified by NIHSS at admission, evolves and may influence patients’ time to hospital arrival. The inclusion of timing in stroke severity assessment remains unclear in stroke research. Oversight of time to assessment can affect prognostic model interpretation, acute clinical decision-making, and the design of future clinical trials by considering admission severity in the context of time since symptom onset.

Aims

This study aimed to assess whether and, if so, how stroke researchers account for time from symptom onset to admission severity assessment in their analyses. We sought to compare this with approaches used by perinatal researchers, considering a similar statistical relationship between gestational age and birth weight.

Summary of review

Two reviewers systematically reviewed papers in leading specialty journals published in 2019 using NIHSS at admission and birth weight respectively as an explanatory factor in the statistical analysis. We targeted a minimum of 50 articles from each field to ensure 90% to identify approaches used in 5% or more of studies.

A total of 111 studies were included. Perinatal researchers considered the temporal variable gestational age more often than time to assessment in stroke studies (89% vs. 7%, chi-squared p<0.001). It was consequently included more often (56% vs. 5%, chi-squared p<0.001). Four methods, including stratification, distribution, regression and combined approaches, were found. Time to assessment was only included as a continuous (n=2) or categorical (n=1) factor alongside admission NIHSS in three studies. Methods for covariate selection, essential for the interpretation of statistical models, were rarely specified.

Conclusions

Few researchers explore the inter-relationship between baseline severity and time to assessment in stroke prognostication, in sharp contrast to consideration of timing in perinatal studies. Future research will investigate whether time to assessment or serial NIHSS in the hyper-acute phase could benefit both clinical practice and stroke research.