Validity
exacerbations of the disease, decompensation
EVENTS, LEAKAGE
With the methodological approach considered, we believe that none of the selected characteristics or the other potentially predictive variables evaluated were associated with a possible phenomenon of “information leakage” from the outcome variable (compensated or decompensated phase) to the predictor variables (“outcome leakage”)We began this study with a cohort of patients in the decompensated phase. This design allowed us to have sufficient observations for both categories of the outcome variable and to develop and evaluate the models obtained (if we had started with a cohort of stable patients, only a small proportion would have presented with decompensation). In addition, the design allowed each patient to act as his or her own control. Although choosing hospitalization as a reference for the decompensated phase was not ideal because the ultimate goal of these algorithms was to detect clinical decompensation in an earlier phase, the evaluation during hospitalization was performed once the patients were clinically stable and were able to walk at least 30 m, so the hospital evaluation (V1) was actually carried out once the most acute phase of decompensation had passed. In the same way, we did not take admission parameters into account because that moment represents the most severe phase of exacerbation, and the aim of this study was to develop an algorithm based on parameters as similar as possible to an earlier phase of exacerbation.The time interval between the standard diagnostic method (confirmation of the compensated or decompensated phase by a doctor) and data collection for the development of the diagnostic models was quite short (24–48 h); therefore, we do not believe that considerable changes in the clinical states of the patients occurred between these events to influence the results for the diagnostic performance of the models developed.In terms of the extrapolation of our results to other populations, the models were designed to detect the most severe exacerbations of the disease (those that prompt hospital admission) and not milder exacerbations (such as those requiring only outpatient management). The inclusion of centers with different levels of complexity in two different geographical areas allowed us to include a sample of patients representing a large part of the clinical spectrum of both pathologies.