Dear Editor,
We would like to thank Alqahtani et al for their interest in our study (Citation1) and their comments, which deserve further discussion.
The main objective of our study was to evaluate, in a retrospective manner, the hypothesis for designing a large prospective trial. As specified in our manuscript, we took care to include patients who were compliant with a rehabilitation programme and experienced a negative event labelled « exacerbation », defined as an adverse event requiring change in medication or hospitalisation (Citation2). Mild exacerbations were intentionally not included in our study, because no clear definition has ever been established and, in clinical practice, may not be clearly reported by patients and simply explained by large day-to-day variability of COPD symptoms. We decided to focus on events leading to relevant clinical implications.
Unfortunately, our retrospective design does not allow us to fully address two other points raised by Alqahtani et al.
First, we were actually unable to report the way exacerbations were confirmed and differentiated from pneumonias or cardiovascular events. We acknowledge that there are different types of COPD exacerbations, with different responses to treatment. Nevertheless, the importance of an early diagnosis of adverse events in clinical practice remains unchanged whatever the cause (Citation3).
Second, we chose to include only COPD patients who experienced at least one exacerbation and therefore we carried out simple and descriptive statistical analysis. From our perspective, use of multivariate regression in a single group of COPD patients with similar characteristics would have been inappropriate. Moreover, baseline characteristics associated with COPD exacerbations during rehabilitation had already been published (Citation4). Of course, more robust models with larger sample size are needed to confirm our results.
We are pleased to provide the cut-off value for 80% sensitivity. In our model, a decrease in 40% of cycle ergometer performance had a sensitivity of 80% (95% CI 68–88) and specificity of 38% (95% CI 26–50), but it was not described initially as it was not the optimal cut-off.
To conclude, our manuscript only highlighted that a simple parameter regularly observed during pulmonary rehabilitation, thus potentially applicable for most patients, could alert clinicians for the risk of exacerbation. Of course, several questions still need to be addressed. Future investigations should therefore 1) include prospectively large sample of patients, 2) correlate performance during session with an EXACT-pro score and physiological parameters, and 3) define more robust statistical models with multivariate regression to isolate independent factors comparing patients characteristics, frequency of exacerbations, rehabilitation compliance, loss in performance during rehabilitation, physiological parameters, etc.
Disclosure statement
The authors declare no conflict of interest.
References
- Comes J, Prieur G, Combret Y, et al. Changes in cycle-ergometer performance during pulmonary rehabilitation predict COPD exacerbation. COPD. 2019;7:1–5.
- Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global strategy for prevention, diagnosis and management of COPD. Fontana, WI: GOLD; 2018.
- Donaldson GC, Law M, Kowlessar B, et al. Impact of prolonged exacerbation recovery in chronic obstructive pulmonary disease. Am J Respir Crit Care Med. 2015;192(8):943–950. doi:10.1164/rccm.201412-2269OC.
- Herer B, Chinet T. Acute exacerbation of COPD during pulmonary rehabilitation: outcomes and risk prediction. COPD. 2018;13:1767–1774. doi:10.2147/COPD.S163472.