Red blood cells distribution width (RDW) predicts survival in cardiovascular diseases. Little is known about the variability of RDW level over time among patients with pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). To our knowledge, RDW has never been analysed as a marker of response to specific treatment.

We retrospectively analysed 77 patients for: i) RDW measured during the last hospitalisation before death or during the last follow-up (RDWlast); ii) mean RDW from all hospitalisations during the entire follow-up of the patient (RDWmean); iii) maximum RDW of all hospitalisations of each patient (RDWmax). In order to assess response to specific treatment and association with prognosis, we compared RDW levels (obtained from 56 patients) before and 3 to 6 months after introduction or intensification of treatment in both the alive and deceased group.

Twenty-eight of 77 patients died, whereas in specific drugs treatment response analysis, 22 of 56 patients died during follow-up. The cut-off values derived from the ROC analysis and assessed using the log-rank test were significant for RDWlast (p<0.0001), RDWmean (p<0.001) and RDWmax (p=0.02). A decrease in RDW levels after introduction or intensification of specific treatment was significant (p=0.015) in survivors, whereas there was no significance (p=0.29) in decrease in RDW levels in non-survivors after change of therapy.

Red blood cells distribution width might be a potential prognostic biomarker in patients with PAH and inoperable CTEPH. The decrease in RDW level after introduction or escalation of PAH-targeted and CTEPH-targeted drugs is associated with a good treatment response and better prognosis.