CRP and pulmonary arterial hypertension: We then apply our proposed MPV rule and its competitors in two case studies, one examining the effect of home elevation (i.e. meters above sea level) on a six-minute walk distance for patients with pulmonary arterial hypertension (PAH), and the other investigating the extent to which C-reactive protein is associated with the risk of mechanical ventilation for patients infected with the novel Coronavirus disease (COVID-19).