Temporal validation of the MMCD score to predict kidney replacement therapy and in-hospital mortality in COVID-19 patients
Authors: das Graças José Ventura Vanessa , Pereira Polianna Delfino , Pires Magda Carvalho , Asevedo Alisson Alves , de Oliveira Jorge Alzira , dos Santos Ana Carolina Pitanga , de Moura Costa André Soares , dos Reis Gomes Angélica Gomides , Lima Beatriz Figueiredo , Pessoa Bruno Porto , Cimini Christiane Corrêa Rodrigues , de Andrade Claudio Moisés Valiense , Ponce Daniela , Rios Danyelle Romana Alves , Pereira Elayne Crestani , Manenti Euler Roberto Fernandes , de Almeida Cenci Evelin Paola , Costa Felício Roberto , Anschau Fernando , Aranha Fernando Graça , Vigil Flavia Maria Borges , Bartolazzi Frederico , Aguiar Gabriella Genta , Grizende Genna Maira Santos , Batista Joanna d’Arc Lyra , Neves João Victor Baroni , Ruschel Karen Brasil , do Nascimento Letícia , de Oliveira Lucas Moyses Carvalho , Kopittke Luciane , de Castro Luís César , Sacioto Manuela Furtado , Carneiro Marcelo , Gonçalves Marcos André , Bicalho Maria Aparecida Camargos , da Paula Sordi Mônica Aparecida , da Cunha Severino Sampaio Natália , Paraíso Pedro Gibson , Menezes Rochele Mosmann , Araújo Silvia Ferreira , de Assis Vivian Costa Morais , de Paula Farah Katia , Marcolino Milena Soriano 
Published: October 2023

Abstract
Background
Acute kidney injury has been described as a common complication in patients hospitalized with COVID-19, which may lead to the need for kidney replacement therapy (KRT) in its most severe forms. Our group developed and validated the MMCD score in Brazilian COVID-19 patients to predict KRT, which showed excellent performance using data from 2020. This study aimed to validate the MMCD score in a large cohort of patients hospitalized with COVID-19 in a different pandemic phase and assess its performance to predict in-hospital mortality.

Methods
This study is part of the “Brazilian COVID-19 Registry”, a retrospective observational cohort of consecutive patients hospitalized for laboratory-confirmed COVID-19 in 25 Brazilian hospitals between March 2021 and August 2022. The primary outcome was KRT during hospitalization and the secondary was in-hospital mortality. We also searched literature for other prediction models for KRT, to assess the results in our database. Performance was assessed using area under the receiving operator characteristic curve (AUROC) and the Brier score.

Results
A total of 9422 patients were included, 53.8% were men, with a median age of 59 (IQR 48–70) years old. The incidence of KRT was 8.8% and in-hospital mortality was 18.1%. The MMCD score had excellent discrimination and overall performance to predict KRT (AUROC: 0.916 [95% CI 0.909–0.924]; Brier score = 0.057). Despite the excellent discrimination and overall performance (AUROC: 0.922 [95% CI 0.914–0.929]; Brier score = 0.100), the calibration was not satisfactory concerning in-hospital mortality. A random forest model was applied in the database, with inferior performance to predict KRT requirement (AUROC: 0.71 [95% CI 0.69–0.73]).

Conclusion
The MMCD score is not appropriate for in-hospital mortality but demonstrates an excellent predictive ability to predict KRT in COVID-19 patients. The instrument is low cost, objective, fast and accurate, and can contribute to supporting clinical decisions in the efficient allocation of assistance resources in patients with COVID-19.