Response To: ‘ Correspondence on ‘haemodynamic Phenotypes and Survival in Patients with Systemic Sclerosis: the Impact of the New Definition of Pulmonary Arterial Hypertension’’ by Iudiciet Al

In their correspondence Iudici et al 1 highlight three important aspects which are to consider in the interpretation of survival data when introducing new thresholds of an early stage of disease.2 They point out, that lead-time bias, length-time bias as well as increasing numbers of patients have to be considered for the new haemodynamic definition of pulmonary arterial hypertension (PAH). In studies investigating the effect of systematic PAH screening programmes on survival in patients with systemic sclerosis, part of the effect of an increased survival may be attributed to lead-time bias and length-time bias.3 4 We agree with Iudici et al that lead-time bias is an important aspect when introducing a new definition of a disease, which includes patients at a less severe stage. This becomes especially important for screening programmes, as survival of screened patients who are diagnosed at early disease stages may implicitly be better compared with patients with a more severe disease. In our study we analysed the frequency of PAH in patients with systemic sclerosis when applying the new PAH definition according to the suggestion from the World Symposium on pulmonary hypertension in Nice 2018. According to a large meta-analysis of haemodynamic data of healthy people, a pulmonary vascular resistance (PVR) >2 Wood Units (WU) …