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" - Martos Pérez, Francisco; Gomez Huelgas, Ricardo; Martín Escalante, María Dolores; Casas Rojo, José Manuel (JMIR Publications, 2021)