Thinking About the Future: A Review of Prognostic Scales Used in Acute Stroke

There is not one survivor in the world than gives a damn about prognostication. They all want to know EXACT stroke rehab protocols and the efficacy rating of them.  Useless.  So you are advocating the nocebo effect whereby survivors should live down to their rehab predictions? Like the many times doctors have told patients; 'You won't recover,  or walk again'.

Thinking About the Future: A Review of Prognostic Scales Used in Acute Stroke

Bogna A. Drozdowska, Sarjit Singh and Terence J. Quinn^*

• Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, United Kingdom

Background: There are many prognostic scales that aim to predict functional outcome following acute stroke. Despite considerable research interest, these scales have had limited impact in routine clinical practice. This may be due to perceived problems with internal validity (quality of research), as well as external validity (generalizability of results). We set out to collate information on exemplar stroke prognosis scales, giving particular attention to the scale content, derivation, and validation.

Methods: We performed a focused literature search, designed to return high profile scales that use baseline clinical data to predict mortality or disability. We described prognostic utility and collated information on the content, development and validation of the tools. We critically appraised chosen scales based on the CHecklist for critical Appraisal and data extraction for systematic Reviews of prediction Modeling Studies (CHARMS).

Results: We chose 10 primary scales that met our inclusion criteria, six of which had revised/modified versions. Most primary scales used 5 input variables (range: 4–13), with substantial overlap in the variables included. All scales included age, eight included a measure of stroke severity, while five scales incorporated pre-stroke level of function (often using modified Rankin Scale), comorbidities and classification of stroke type. Through our critical appraisal, we found issues relating to excluding patients with missing data from derivation studies, and basing the selection of model variable on significance in univariable analysis (in both cases noted for six studies). We identified separate external validation studies for all primary scales but one, with a total of 60 validation studies.

Conclusions: Most acute stroke prognosis scales use similar variables to predict long-term outcomes and most have reasonable prognostic accuracy. While not all published scales followed best practice in development, most have been subsequently validated. Lack of clinical uptake may relate more to practical application of scales rather than validity. Impact studies are now necessary to investigate clinical usefulness of existing scales.

Introduction

Outcomes following a stroke event can range from full recovery, through varying degrees of disability to death. Given the subsequent need for intervention planning, resource use, and lifestyle adjustments, predicting outcome following stroke is of key interest and importance to patients, their families, clinicians, and hospital administrators. Various tools exist to assist in estimating stroke-related prognosis. For example, the ABCD2 score uses clinical features to predict risk of stroke following transient ischemic attack (TIA) (1). Although there are criticisms of ABCD2, it is widely used and included in stroke guidelines (2).

Scales for predicting acute stroke outcomes from baseline features are also described in the scientific literature (3–5). Often prognosis scales report mortality; however, given the disabling nature of stroke, scales predicting death and/or longer-term disability may be more useful in the stroke setting (6). However, these prognostic scales have had limited clinical traction and have not been incorporated into routine clinical practice (3). There are many plausible reasons why these scales have not been adopted by the stroke community (6). In an acute setting, scales may be perceived as being too complex to use or may require information that is not routinely available (for example, sophisticated neuroimaging) (3). Clinicians may moreover be concerned that scales are inherently too generic, and may not provide insight over what the clinician can conclude based on individual patient factors and clinical gestalt (7).

For many scales, clinicians may simply not be convinced of their utility or the rigor of the underpinning science. These points can be addressed by describing the validity of the scales. Issues with validity could relate to the methodological quality of the initial derivation of the scale (internal validity) or the generalizability of a scale to a real-world population (external validity). Robust evidence of validity requires assessment of the scale in cohorts independent of the population used to derive that scale (8). However, In some areas of stroke practice, for example rehabilitation, it has been demonstrated that independent validation studies are lacking for many scales (5).

Collating evidence around the quality of the research that led to development of prognostic scales and also the results of subsequent validation work could be useful for various stakeholders. For clinicians it may convince of the utility, or lack of utility, of certain tools; for researchers it may point to common methodological limitations that need to be addressed in future work and for policy developers, if a certain tool has a more compelling evidence base than others, then this scale may be preferred in guidelines.

Previous reviews have reported that many stroke prognosis scales have similar properties such as discrimination and calibration. These reviews also highlight the limited evidence for external validity of many commonly used stroke scales (9, 10). Distinguishing an optimal prognostic tool may not be possible based on psychometric properties alone and factors such as feasibility and acceptability in the real world setting need to be considered.

We sought to collate and appraise a selection of exemplar published stroke scales, designed for use in acute care settings. We used these as a platform to discuss methodological quality of prognostic scale development, while also considering potential barriers or facilitators to implementation of the scales in clinical practice.