External validation of the QCovid risk prediction algorithm for risk of COVID-19 hospitalisation and mortality in adults: national validation cohort study in Scotland

Colin R. Simpson, Chris Robertson, Steven Kerr, Ting Shi, Eleftheria Vasileiou, Emily Moore, Colin McCowan, Utkarsh Agrawal, Annemarie Docherty, Rachel Mulholland, Josie Murray, Lewis Duthie Ritchie, Jim McMenamin, Julia Hippisley-Cox, Aziz Sheikh

Research output: Contribution to journalArticlepeer-review

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Abstract

BACKGROUND: The QCovid algorithm is a risk prediction tool that can be used to stratify individuals by risk of COVID-19 hospitalisation and mortality. Version 1 of the algorithm was trained using data covering 10.5 million patients in England in the period 24 January 2020 to 30 April 2020. We carried out an external validation of version 1 of the QCovid algorithm in Scotland. 

METHODS: We established a national COVID-19 data platform using individual level data for the population of Scotland (5.4 million residents). Primary care data were linked to reverse-transcription PCR (RT-PCR) virology testing, hospitalisation and mortality data. We assessed the performance of the QCovid algorithm in predicting COVID-19 hospitalisations and deaths in our dataset for two time periods matching the original study: 1 March 2020 to 30 April 2020, and 1 May 2020 to 30 June 2020. 

RESULTS: Our dataset comprised 5 384 819 individuals, representing 99% of the estimated population (5 463 300) resident in Scotland in 2020. The algorithm showed good calibration in the first period, but systematic overestimation of risk in the second period, prior to temporal recalibration. Harrell's C for deaths in females and males in the first period was 0.95 (95% CI 0.94 to 0.95) and 0.93 (95% CI 0.92 to 0.93), respectively. Harrell's C for hospitalisations in females and males in the first period was 0.81 (95% CI 0.80 to 0.82) and 0.82 (95% CI 0.81 to 0.82), respectively. 

CONCLUSIONS: Version 1 of the QCovid algorithm showed high levels of discrimination in predicting the risk of COVID-19 hospitalisations and deaths in adults resident in Scotland for the original two time periods studied, but is likely to need ongoing recalibration prospectively.

Original languageEnglish
Pages (from-to)497-504
Number of pages8
JournalThorax
Volume77
Issue number5
Early online date15 Nov 2021
DOIs
Publication statusPublished - May 2022

Bibliographical note

Acknowledgments
The authors would like to thank staff at Public Health Scotland, Albasoft Ltd, the general practices that contributed data to the study and the EAVE II Collaborators. AS, JM and CR serve on The Scottish Government’s COVID-19 Chief Medical Officer’s Advisory Group and the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) Risk Stratification Subgroup.

Ethics approval
Ethical permission for this study was granted from South East Scotland Research Ethics Committee 02 (12/SS/0201). The Public Benefit and Privacy Panel Committee of Public Health Scotland, approved the linkage and analysis of the deidentified datasets for this project (1920-0279).

Data Availability Statement

All code, metadata and documentation for this project is publicly available at https://github.com/EAVE-II/Qcovid-validation. A data dictionary is available at https://github.com/EAVE-II/EAVE-II-data-dictionary. Most of the data that were used in this study are highly sensitive and will not be made available publicly

Keywords

  • clinical epidemiology
  • COVID-19

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