A workup to identify alternative aetiologies included CT chest, sputum microbiology, inflammatory markers (CRP, ESR, white blood cell count), a d-dimer (a fibrin degradation product indicative of thromboembolic disease when elevated) and pro-BNP (brain natriuretic protein, as a marker for increased atrial stretch indicative of change in right heart pressures) were all within normal limits or unchanged from baseline. This evidence concerns the gene CRP and Thromboembolism.