Skip to main content

Accuracy of automated computer-aided risk scoring systems to estimate the risk of COVID-19: a retrospective cohort study

Abstract

Background

In the UK National Health Service (NHS), the patient’s vital signs are monitored and summarised into a National Early Warning Score (NEWS) score. A set of computer-aided risk scoring systems (CARSS) was developed and validated for predicting in-hospital mortality and sepsis in unplanned admission to hospital using NEWS and routine blood tests results. We sought to assess the accuracy of these models to predict the risk of COVID-19 in unplanned admissions during the first phase of the pandemic.

Methods

Adult ( > = 18 years) non-elective admissions discharged (alive/deceased) between 11-March-2020 to 13-June-2020 from two acute hospitals with an index NEWS electronically recorded within ± 24 h of admission. We identified COVID-19 admission based on ICD-10 code ‘U071’ which was determined by COVID-19 swab test results (hospital or community). We assessed the performance of CARSS (CARS_N, CARS_NB, CARM_N, CARM_NB) for predicting the risk of COVID-19 in terms of discrimination (c-statistic) and calibration (graphically).

Results

The risk of in-hospital mortality following emergency medical admission was 8.4% (500/6444) and 9.6% (620/6444) had a diagnosis of COVID-19. For predicting COVID-19 admissions, the CARS_N model had the highest discrimination 0.73 (0.71 to 0.75) and calibration slope 0.81 (0.72 to 0.89) compared to other CARSS models: CARM_N (discrimination:0.68 (0.66 to 0.70) and calibration slope 0.47 (0.41 to 0.54)), CARM_NB (discrimination:0.68 (0.65 to 0.70) and calibration slope 0.37 (0.31 to 0.43)), and CARS_NB (discrimination:0.68 (0.66 to 0.70) and calibration slope 0.56 (0.47 to 0.64)).

Conclusions

The CARS_N model is reasonably accurate for predicting the risk of COVID-19. It may be clinically useful as an early warning system at the time of admission especially to triage large numbers of unplanned admissions because it requires no additional data collection and is readily automated.

Peer Review reports

Introduction

The novel coronavirus SARS-CoV-2, which was declared as a pandemic on 11-March 2020, which produces the newly identified disease ‘COVID-19’ in patients with symptoms (Coronaviridae Study Group of the International Committee on Taxonomy of Viruses [1]), has challenged health care systems worldwide.

Patients with COVID-19 admitted to a hospital can develop severe disease with life-threatening respiratory and/or multi-organ failure [2, 3] with a high risk of mortality. It is recommended that patients at risk of deterioration are referred to critical care. The appropriate early assessment and management of patients with COVID-19 are important in ensuring high-quality care [4, 5].

In the UK National Health Service (NHS), the patient’s vital signs are monitored and summarised into a National Early Warning Score (NEWS) [6]. NEWS is calculated from six physiological variables or vital signs—respiration rate, oxygen saturation, temperature, systolic blood pressure, heart rate and level of consciousness (alert, voice, pain, unresponsive) and use of supplemental oxygen. NEWS points are allocated according to clinical observations (see Table S1).

We have developed four automated, computer-aided risk scores to predict the patient’s risk of mortality (CARM_N & CARM_NB) and sepsis (CARS_N & CARS_NB) following emergency medical admission to hospital [7,8,9,10]. The _N models use NEWS and the _NB models incorporate routine blood test results. We refer to this suite of risk equations as computer-aided risk scoring systems (CARSS).

Our aim in this study was to assess the accuracy of CARSS in predicting the risk of COVID-19 in unplanned admissions to a teaching hospital during the first phase of the novel coronavirus SARS CoV-2 (COVID-19) pandemic. We are not developing new risk prediction models, we are assessing the performance of existing models, re-purposed for COVID-19.

Methods

Setting & data

Our cohort of unplanned admissions is from two acute hospitals which are approximately 65 km apart in the Yorkshire & Humberside region of England—Scarborough hospital (n 300 beds) and York Hospital (YH) (n 700 beds), managed by York Teaching Hospitals NHS Foundation Trust. For this study, the two acute hospitals are combined into a single dataset and analysed collectively. The hospitals have electronic NEWS scores and vital signs recording which is routinely collected as part of the patient’s process of care (see Table S1).

We considered all adult (age ≥ 18 years) emergency medical admissions (excluding ambulatory care area patients), discharged (alive/deceased) during 3 months (11 March 2020 to 13 June 2020), with electronic NEWS recorded within ± 24 h of admission. This on-admission NEWS score is referred to as the index NEWS.

For each emergency admission, we obtained a pseudonymised patient identifier, patient’s age (years), gender (male/female), discharge status (alive/dead), admission and discharge date and time, diagnoses codes based on the 10th revision of the International Statistical Classification of Diseases (ICD-10) [11, 12], NEWS (including its subcomponents respiratory rate [breaths per minute], temperature [oC], systolic pressure [mmHg], pulse rate [beats per minute], oxygen saturation [percentage], oxygen supplementation [yes/no], and alertness level [alert, voice, pain, unconscious] ) [6, 13], blood test results (albumin [g/L], creatinine [umol/L], haemoglobin [g/l], potassium [mmol/L], sodium [mmol/L], urea [mmol/L], and white cell count [109 cells/L]), and Acute Kidney Injury (AKI) score.

Table 1 Four risk scores for predicting the risk of mortality and sepsis, known as computer-aided risk scoring systems (CARSS)

We had developed and externally validated four risk scores: (1) CARM_N for predicting in-hospital mortality based on NEWS [10]; (2) CARM_NB for predicting in-hospital mortality that incorporates routine blood test results [7]; CARS_N for predicting sepsis based on NEWS [9]; CARS_NB for predicting sepsis that incorporates routine blood test results [8] (see Table 1). These four equations are collectively known as computer-aided risk scoring systems (CARSS), calculated using index NEWS and blood test results. We excluded records where the index NEWS (or blood test results) was not within ± 24 h (± 96 h) or was missing/not recorded at all (see Table S2).

The ICD-10 code ‘U071’ was used to identify records with COVID-19. We searched primary and secondary ICD-10 codes for ‘U071’ for identifying COVID-19. We also linked positive laboratory results for COVID-19 swabs to an automated diagnostic coding entry in the patient electronic health record.

Statistical analyses

We report discrimination and calibration statistics as performance measures for CARSS [14].

We determined the discrimination of CARSS using the concordance statistic (c-statistic) that gives the probability of randomly selected patients who experienced COVID-19 had a higher risk score than a Non-Covid-19 patient. For a binary outcome (COIVD-19/Non-Covid-19), the c-statistic is the area under the Receiver Operating Characteristics (ROC) curve [15]. The ROC curve is a plot of the sensitivity, (true positive rate), versus 1-specificity, (false positive rate), for consecutive predicted risks. A c-statistic of 0.5 is no better than tossing a coin, whilst a perfect model has a c-statistic of 1. In general, values less than 0.7 are considered to show poor discrimination, values of 0.7 to 0.8 can be described as reasonable, and values above 0.8 suggest good discrimination [16].

Calibration measures a model’s ability to generate predictions that are on average close to the average observed outcome and can be readily seen on a scatter plot (y-axis observed risk, x-axis predicted risk). Perfect predictions should be on the 45° line. We internally validated and assessed the calibration for all the models using the bootstrapping approach [17, 18]. The overall statistical performance was assessed using the scaled Brier score which incorporates both discrimination and calibration [14]. The Brier score is the squared difference between actual outcomes and predicted risk of COVID-19, scaled by the maximum Brier score such that the scaled Brier score ranges from 0 to 100%. Higher values indicate superior models. The 95% confidence interval for the scaled Brier score was calculated using bootstrap approach [19].

We followed the STROBE guidelines to report the findings [20]. All analyses were undertaken using R [21] and Stata [22]. The 95% confidence interval for the c-statistic was computed using DeLong’s method as implemented in the pROC library [23].

Results

Cohort description

There were 6480 discharges over 3 months. We excluded 36 (0.6%) records because the index NEWS was not recorded within ± 24 h of the admission date/time or NEWS was missing or not recorded at all (see Table S2). We further excluded 1175 (18.1%) because absence of blood test results.

The prevalence of COVID-19 was 9.6% (620/6444) and of these 32% (199/620) deceased at discharge. The demographic, vital signs and outcome profiles of the COVID-19 versus non-COVID-19 admissions and discharge deceased versus discharged alive are shown in Table 2 and Figure S1-S2. COVID-19 admissions were older (73.3 vs. 67.7, p < 0.001), more likely to be male (54.7% vs. 50.1%, p < 0.001), with higher index NEWS (4.0 vs. 2.5, p < 0.001). They also had longer hospital stay (7.3 days vs. 3.0 days, p < 0.001) and higher in-hospital mortality (32.1% vs. 5.8%, p < 0.001). The average CARSS (CARM_N, CARM_NB, CARS_N, CARS_NB) risk was generally higher for COVID-19 admissions and for those who were deceased at discharge.

Statistical modelling results

We assessed the four CARSS models (CARM_N, CARM_NB, CARS_N, CARS_NB) performance according to discrimination (c-statistic) and calibration (graphically) in predicting the risk of COVID-19 (see Table 3; Figs. 1 and 2).

Fig. 1
figure 1

Receiver Operating Characteristic curve for four CARSS models in predicting the risk of COVID-19. CARM_N: for predicting mortality with NEWS data only; CARM_NB: for predicting mortality with NEWS and Blood test results data; CARS_N: for predicting sepsis with NEWS data only; CARS_NB: for predicting sepsis with NEWS and Blood test results data

Fig. 2
figure 2

External validation of CARSS models, respectively for predicting the risk of COVID-19. NB: We limit the risk of COVID-19 to 0.40 for visualisation purpose because beyond this point, we have few patients

For predicting COVID-19 admissions, the CARS_N model performed better than others in terms of discrimination 0.73 (95%CI 0.71 to 0.75) and calibration slope 0.81 (95%CI 0.72 to 0.89) compared to other CARSS models: CARM_N (discrimination: 0.68 (0.66 to 0.70) and calibration slope 0.47 (0.41 to 0.54)), CARM_NB (discrimination: 0.68 (0.65 to 0.70) and calibration slope 0.37 (0.31 to 0.43)), and CARS_NB (discrimination: 0.68 (0.66 to 0.70) and calibration slope 0.56 (0.47 to 0.64)).

Table 2 Characteristics of emergency medical admissions in COVID-19 versus non-COVID-19 who discharged alive/deceased
Table 3 Performance of CARSS models for predicting the risk of COVID-19

Discussion

We assessed the performance of four computer-aided risk scores to predict the risk of COVID-19 in unplanned admissions to hospital. We found that the CARS_N model for sepsis (based on NEWS) had the best performance for predicting the risk of COVID-19. CARS_N was developed for predicting sepsis and we found it has good discrimination and calibration compared to other CARSS models. This may reflect the reported overlap in features between sepsis and COVID-19, such as hyper inflammation and coagulopathy which also contribute to disease severity and death in COVID-19 patients [24]. Zhou et al. [25] found that the Sequential Organ Failure Assessment (SOFA) score (for sepsis) is associated with in-hospital mortality in COVID-19 patients.

A recent systematic review identified models to predict mortality from COVID-19 with c-statistics that ranged from 0.87 to 1 [26]. However, despite these high c-statistics, the review authors cautioned against the use of these models in clinical practice because of the high risk of bias and poor reporting of studies which are likely to have led to optimistic results [26]. The main advantages of our models are that they are (1) rigorously developed and externally validated, (2) designed to incorporate data which are already available in the patient’s electronic health record thus place no additional data collection or computational burden on clinicians and (3) are readily automated. The CARS_N model is particularly attractive because it uses NEWS data which can be available within a short while (< 30 min) of admission and so can support early clinical decision making about patients, which is essential to ensuring safe, high quality care.

There are several limitations to our study: (1) This data is from a single NHS Trust, and to understand the extent to which these findings are generalisable, further study is required (2) We used the index NEWS and blood test results which reflects the ‘on-admission’ risk of mortality of the patients. Nonetheless, NEWS and blood test results are repeatedly updated for each patient according to local hospital protocols (Figure S5 in supplementary material) (3) We identified COVID-19 based on ICD-10 code ‘U071’ which was determined by COVID-19 swab test results (hospital or community) and clinical judgment and so our findings are constrained by the accuracy of these methods [27, 28] (4) We have used NEWS in our data but since the NEWS2 is now widely used, further study is required to determine the accuracy of NEWS2 based models [29].

Conclusion

The CARS_N model is reasonably accurate for predicting the risk of COVID-19. It may be clinically useful as an early warning system at the time of admission especially to triage large numbers of unplanned admissions because it requires no additional data collection and is readily automated.

Data availability

The data that support the findings of this study are available from NHS York hospital trust but restrictions apply to the availability of these data, which were used under license for the current study, and so are not publicly available. However, if anyone is interested in the data, then they should contact the R&D offices in the first instance https://www.research.yorkhospitals.nhs.uk/about-us1/our-directorates/.

References

  1. Gorbalenya AE, Baker SC, Baric RS, de Groot RJ, Drosten C, Gulyaeva AA, et al. The species severe acute respiratory syndrome-related coronavirus: classifying 2019-nCoV and naming it SARS-CoV-2. Nat Microbiol. 2020;5:536–44. https://doi.org/10.1038/s41564-020-0695-z.

    Article  CAS  Google Scholar 

  2. Onder G, Rezza G, Brusaferro S. Case-fatality rate and characteristics of patients dying in relation to COVID-19 in Italy. JAMA - J Am Med Association. 2020;323:1775–6. https://doi.org/10.1001/jama.2020.4683.

    Article  CAS  Google Scholar 

  3. Vincent JL, Taccone FS. Understanding pathways to death in patients with COVID-19. Lancet Respiratory Med. 2020;8:430–2. https://doi.org/10.1016/S2213-2600(20)30165-X.

    Article  CAS  Google Scholar 

  4. Hao B, Sotudian S, Wang T, Xu T, Hu Y, Gaitanidis A, et al. Early prediction of level-of-care requirements in patients with COVID-19. Elife. 2020;9:1–23. https://doi.org/10.7554/ELIFE.60519.

    Article  Google Scholar 

  5. Wang T, Paschalidis A, Liu Q, Liu Y, Yuan Y, Paschalidis IC. Predictive models of mortality for hospitalized patients with COVID-19: Retrospective Cohort Study. JMIR Med Inf. 2020;8. https://doi.org/10.2196/21788.

  6. Royal College of Physicians. National Early Warning Score (NEWS): Standardising the assessment of acuteillness severity in the NHS - Report of a working party. 2012. https://www.rcplondon.ac.uk/file/32/download.

  7. Faisal M, Scally A, Jackson N, Richardson D, Beatson K, Howes R et al. Oct. Development and validation of a novel computer-aided score to predict the risk of in-hospital mortality for acutely ill medical admissions in two acute hospitals using their first electronically recorded blood test results and vital signs: a cross-section. BMJ Open (accepted 2018). 2018.

  8. Faisal M, Scally A, Richardson D, Beatson K, Howes R, Speed K, et al. Development and external validation of an automated computer-aided risk score for predicting sepsis in emergency medical admissions using the patient’s first electronically recorded vital signs and blood test results. Crit Care Med. 2018;46:612–8. https://doi.org/10.1097/CCM.0000000000002967.

    Article  PubMed  Google Scholar 

  9. Faisal M, Richardson D, Scally AJ, Howes R, Beatson K, Speed K, et al. Computer-aided national early warning score to predict the risk of sepsis following emergency medical admission to hospital: a model development and external validation study. CMAJ. 2019;191:E382–9. https://doi.org/10.1503/cmaj.181418.

    Article  PubMed  PubMed Central  Google Scholar 

  10. Faisal M, Richardson D, Scally A, Howes R, Beatson K, Mohammed M. Performance of externally validated enhanced computer-aided versions of the National Early warning score in predicting mortality following an emergency admission to hospital in England: a cross-sectional study. BMJ Open. 2019;9.

  11. Organization WH. ICD-10: international statistical classification of diseases and related health problems: tenth revision. https://apps.who.int/iris/handle/10665/42980.

  12. Jolley RJ, Quan H, Jetté N, Sawka KJ, Diep L, Goliath J, et al. Validation and optimisation of an ICD-10-coded case definition for sepsis using administrative health data. BMJ Open. 2015;5:e009487.

    Article  PubMed  PubMed Central  Google Scholar 

  13. Royal College of Physicians. NHS England approves use of National Early Warning Score (NEWS. ) 2 to improve detection of acutely ill patients. 2017. https://www.rcplondon.ac.uk/news/nhs-england-approves-use-national-early-warning-score-news-2-improve-detection-acutely-ill.

  14. Steyerberg EW. Clinical prediction models. A practical approach to development, validation and updating. Springer; 2008.

  15. Steyerberg EW, Vickers AJ, Cook NR, Gerds T, Gonen M, Obuchowski N, et al. Assessing the performance of prediction models: a framework for traditional and novel measures. Epidemiology. 2010;21:128–38.

    Article  PubMed  PubMed Central  Google Scholar 

  16. Hanley JA, McNeil BJ. The meaning and use of the area under a receiver operating characteristic (ROC) curve. Radiology. 1982;143:29–36.

    Article  CAS  PubMed  Google Scholar 

  17. Steyerberg EW, Harrell FE, Borsboom GJJ, Eijkemans MJ, Vergouwe Y, Habbema JDF. Internal validation of predictive models: efficiency of some procedures for logistic regression analysis. J Clin Epidemiol. 2001;54:774–81.

    Article  CAS  PubMed  Google Scholar 

  18. Harrell FE. rms: Regression Modeling Strategies http://cran.r-project.org/package=rms. 2015.

  19. Mantalos P, Zografos K. Interval estimation for a binomial proportion: a bootstrap approach. http://dx.doi.org/101080/00949650701749356. 2008;78:1251–65. https://doi.org/10.1080/00949650701749356.

  20. Von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP. The strengthening the reporting of Observational studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. PLoS Med. 2007;4:1623–7. https://doi.org/10.1371/journal.pmed.0040296.

    Article  Google Scholar 

  21. R Development Core Team. R: A language and environment for statistical computing. R Foundation for Statistical Computing http://www.r-project.org/. 2015.

  22. StatCorp, Stata. Release 14. Statistical Software. College Station, TX: StataCorp LP; 2016.

    Google Scholar 

  23. Robin X, Turck N, Hainard A, Tiberti N, Lisacek F, Sanchez JJ-CC, et al. pROC: an open-source package for R and S + to analyze and compare ROC curves. BMC Bioinformatics. 2011;12:77.

    Article  PubMed  PubMed Central  Google Scholar 

  24. Beltrán-García J, Osca-Verdegal R, Pallardó FV, Ferreres J, Rodríguez M, Mulet S, et al. Sepsis and coronavirus disease 2019. Crit Care Med. 2020;Publish Ah:1–4.

    Google Scholar 

  25. Zhou F, Yu T, Du R, Fan G, Liu Y, Liu Z, et al. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. Lancet. 2020;395:1054–62. https://doi.org/10.1016/S0140-6736(20)30566-3.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  26. Wynants L, Van Calster B, Collins GS, Riley RD, Heinze G, Schuit E, et al. Prediction models for diagnosis and prognosis of covid-19: systematic review and critical appraisal. BMJ. 2020;369:18. https://doi.org/10.1136/bmj.m1328.

    Article  Google Scholar 

  27. Corfield AR, Lees F, Zealley I, Houston G, Dickie S, Ward K et al. Utility of a single early warning score in patients with sepsis in the emergency department. 2012.

  28. Churpek MM, Snyder A, Han X, Sokol S, Pettit N, Howell MD, et al. Quick Sepsis-related Organ failure Assessment, systemic inflammatory response syndrome, and early warning scores for detecting clinical deterioration in infected patients outside the Intensive Care Unit. Am J Respir Crit Care Med. 2017;195:906–11.

    Article  PubMed  PubMed Central  Google Scholar 

  29. Faisal M, Mohammed M, Richardson D, Fiori M, Beatson K. Development and validation of automated computer-aided risk scores to predict in-hospital mortality for emergency medical admissions with COVID-19: a retrospective cohort development and validation study. BMJ Open. 2022;12:e050274. https://doi.org/10.1136/BMJOPEN-2021-050274.

    Article  PubMed  Google Scholar 

Download references

Acknowledgements

For the purposes of open access, the author has applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising from this submission.

Funding

This research was supported by the Health Foundation. The Health Foundation (Award No 7380) is an independent charity working to improve the quality of healthcare in the UK.

This research was supported by the National Institute for Health and Care Research (NIHR) Yorkshire and Humber Patient Safety Research Collaboration (NIHR Yorkshire and Humber PSRC). The views expressed in this article are those of the authors and not necessarily those of the NHS, the Health Foundation, the NIHR, or the Department of Health and Social Care.

Author information

Authors and Affiliations

Authors

Contributions

MFa and MAM had the original idea for the work. KB and MFi provided the data extracts. MFa undertook the statistical analyses with support from MAM. MFa, MAM, and DR wrote the first draft of the paper. DR provided clinical perspectives. All others contributed to the final paper and have approved the final version. MAM & MFa will act as study guarantors.

Corresponding author

Correspondence to Mohammed Amin Mohammed.

Ethics declarations

Ethics approval and consent to participate

This study used anonymised data and received ethical approval from the Health Research Authority (HRA) and Research Ethics Committee (REC) of Health and Care Research Wales (HCRW). Ethical approval was granted by the Leeds Ethics committee (reference number 19/HRA/0548). All methods were carried out in accordance with relevant guidelines and regulations. The informed consent to participate is not applicable as this is retrospective study and used only anonymised data. The requirement for informed consent was waived by the Leeds Ethics Committee (reference number 19/HRA/0548) because of the retrospective nature of the study.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Role of the funding source

The funders of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary Material 1

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Faisal, M., Mohammed, M.A., Richardson, D. et al. Accuracy of automated computer-aided risk scoring systems to estimate the risk of COVID-19: a retrospective cohort study. BMC Res Notes 17, 109 (2024). https://doi.org/10.1186/s13104-024-06773-0

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1186/s13104-024-06773-0

Keywords