One in six Australians with pulmonary arterial hypertension remain on a single drug despite the severity of their disease meriting combination therapy, a study shows.

The lack of PBS subsidy for combination therapy may explain the apparent failure to prescribe it regardless of the recommendations in international guidelines, the authors write in Heart, Lung and Circulation.

In a cross-sectional study of 1046 patients from the Pulmonary Hypertension Society of Australia and New Zealand Registry, results showed 51% were on monotherapy and 49% on combination therapy.

Among those on monotherapy, 34% failed to meet low-risk criteria “and should be considered inadequately treated”, said the authors, from specialist centres across Australia.