RT Journal Article T1 Minimizing Selection and Classification Biases. Comment on "Clinical Characteristics and Prognostic Factors for Intensive Care Unit Admission of Patients With COVID-19: Retrospective Study Using Machine Learning and Natural Language Processing". A1 Martos-Perez, Francisco A1 Gómez-Huelgas, Ricardo A1 Martin-Escalante, Maria Dolores A1 Casas-Rojo, Jose Manuel K1 COVID-19 K1 SARS-CoV-2 K1 Artificial intelligence K1 Big data K1 Classification bias K1 Critical care K1 Electronic health records K1 Predictive model K1 Prognosis K1 Tachypnea AB The paper by Izquierdo et al [1], published in the recent issue of the Journal of Medical Internet Research, employed a combination of conventional and machine learning tools to describe the clinical characteristics of patients with COVID-19 and the factors that predict intensive care unit (ICU) admission. We would like to make some comments about its design. The authors should have provided the proportion of patients with a positive microbiological diagnosis. If the artificial intelligence software’s capacity for retrieving this information is limited in some way, this should be explained. The classification bias introduced by the lack of microbiological confirmation may have been significant since the study includes patients from January 1, 2020. Although some undiagnosed cases have likely been present prior to the first declared case (March 1, 2020) [2] in Castilla-La Mancha, it is improbable that there were many of them. PB JMIR Publications YR 2021 FD 2021-05-26 LK http://hdl.handle.net/10668/17792 UL http://hdl.handle.net/10668/17792 LA en NO Martos Pérez F, Gomez Huelgas R, Martín Escalante MD, Casas Rojo JM. Minimizing Selection and Classification Biases. Comment on "Clinical Characteristics and Prognostic Factors for Intensive Care Unit Admission of Patients With COVID-19: Retrospective Study Using Machine Learning and Natural Language Processing". J Med Internet Res. 2021 May 26;23(5):e27142 DS RISalud RD Sep 4, 2025