Aléxia Gabriela Silva Vieira, Ana Carolina Pereira Nunes Pinto, Amanda Alves Assis Garcia, Ricardo Kenji Nawa, Caroline Gomes Mól, Josué DR Duenas, Álvaro N Atallah, Gentle S Shrestha, Marcus J Schultz, Humberto Saconato, Virginia FM Trevisani
Version published: 29 June 2026
https://doi.org/10.1002/14651858.CD016115
Abstract
Objectives
This is a protocol for a Cochrane Review (prognosis). The objectives are as follows:
To determine whether prognostic models can be used for predicting the occurrence of ICU admission and mortality within the index hospital admission, and post‐discharge survival at reported follow‐up time points, up to one year, in critically ill adults not yet admitted to the ICU.
The objective in PICOTS format is as follows.
- Population: critically ill adults not yet admitted to the ICU
- Index prognostic model: available prognostic models with or without external validation
- Comparator: not applicable
- Outcomes: ICU admission, ICU and hospital mortality, and post‐discharge survival
- Timing: for ICU admission or transfer, ICU mortality, and hospital mortality outcomes, the timing will be in hospital. For post‐discharge survival, the timing will be up to 28 days, 1 to 3 months, 6 months, and 1 year after hospital discharge.
- Setting: acute hospital wards and emergency care departments
Background
Description of the health condition and context
In 2021, the worldwide average of intensive care unit (ICU) beds was 8.73 per 100,000 people across 87 countries, with patients staying between 5 and 18.5 days [1, 2]. The length of ICU stay is commonly affected by the severity of illness of the patient, and can be influenced by care management timeliness. Unplanned or delayed ICU admissions are concerning, and impact about 9% to 40% of patients [3, 4]. Nearly 90% of such admissions result from new or worsening conditions and delayed recognition of clinical deterioration [5, 6], thus increasing costs, the healthcare providers' workload, and the risk of serious adverse events (such as cardiac arrest) and death [7, 8]. Predicting admission to ICU and mortality by using prognostic models, especially in patients not yet admitted to the ICU, may be key to promoting individualised and patient‐centered care in potentially critically ill patients.
Description of the prognostic model
A prognostic model is a mathematical equation that integrates multiple predictors to provide a reliable estimate of an individual's risk of experiencing a specific outcome [9, 10]. These models may incorporate a range of predictive factors, such as clinical and physiological parameters, and generate a numerical estimate of the risk of outcomes including mortality, prolonged hospitalisation, and adverse events (e.g. cardiac arrest) [11, 12, 13, 14]. To date, no prognostic model has been established as a gold standard for predicting ICU admission or mortality outside the ICU. This may be partly explained by the heterogeneity of these patient populations assessed in different clinical settings, such as hospital emergency departments and acute hospital wards, with varying severity of illness, comorbidities, and timing of assessment. Heterogeneity may also arise from differences in healthcare resources, monitoring capacity, escalation pathways, ICU admission thresholds, and geo‐economic contexts. In addition, the prediction of ICU admission is particularly challenging because this outcome is partly resource‐dependent. Even when a model accurately identifies patients with greater clinical severity or higher risk, ICU admission may not occur if ICU beds are unavailable or if local admission thresholds differ. Although most models have undergone extensive validation, primarily in high‐income countries, their predictive performance varies [15, 16, 17, 18, 19, 20, 21]. Also, the range of outcomes assessed in published systematic reviews remains limited [22, 23, 24].
Why it is important to do this review
Several systematic reviews have evaluated prognostic models for patients cared outside the ICU. However, they considered a limited set of outcomes, such as mortality, length of stay, and models’ accuracy for predicting the outcomes. In addition, there were methodological limitations, such as limited search strategy, absence of tools to assess risk of bias, and limited inclusion of different prognostic models [14, 22, 25, 26, 27, 28, 29, 30]. A comprehensive search strategy is needed to identify methodologically sound models for predicting admission to ICU and mortality in critically ill adults. This evaluation should consider various settings and patient profiles to improve equity, personalisation, and accuracy in decision‐making. This review is highly relevant to physicians who must choose whether to request an ICU bed, a change to the patient care plan, or recommend surveillance. It is also relevant to conduct future research on external validation of existing prognostic models, potential impact studies of such models, and research on developing new prognostic models.
Read the full protocol on the Cochrane Library