Patient-related outcome shows strong link to survival in PAH

By Lucy Piper, Senior medwireNews Reporter

Health-related quality of life (HRQoL) is strongly associated with survival in patients with pulmonary arterial hypertension (PAH), making it a reasonable target for treatment, study findings suggest.

The association persisted after accounting for patient characteristics, and disease type and severity, note the study researchers.

Led by Stephen Mathai (Johns Hopkins University School of Medicine, Maryland, USA), they used the Short Form (SF)-36 survey to measure HRQoL in 87 PAH patients, the majority of whom were women aged an average of 56 years with a World Health Organization (WHO) functional class of III or IV.

Significant differences from US normative values were seen for six of eight SF-36 domains. The PAH patients had lower physical and mental component summary scores and scored lower on the physical domains of physical function, role physical and general health, and the mental domain vitality. The researchers note, however, that the patients actually scored better than US norms on two domains – body pain and mental health.

All domains and summary scores were strongly associated with WHO functional class and particularly patient performance on the 6-minute walk distance test (6MWT), but there were no significant relationships with haemodynamic measurements.

Over a median follow-up of 3.8 years, 40 of the patients died and two received lung transplants. With every 1-point increase in each of the physical function, role physical and body pain domains, the chances of transplant-free survival increased by 2%. The same increase in the mental health domain, the mental component summary score and the physical component summary score increased the chances by 3%, 3% and 5%, respectively.

“Thus, even small changes in these parameters may have a significant relationship to outcomes in PAH”, note Mathai and team in the Annals of the American Thoracic Society.

The six HRQoL parameters, including all four physical function domains, and the physical and mental component summary scores remained significantly associated with survival after taking into account age, disease type (idiopathic versus systemic sclerosis-associated) and disease severity.

But after adjustment for cardiac index, the physical component summary score no longer predicted survival. Accounting for WHO functional class confounded the relationship between many of the SF-36 domains, most notably the physical domains, and survival, whereas the magnitude of the association between the mental component summary score and survival remained stable.

Mathai and colleagues say their findings highlight the importance of a patient-reported outcome as a primary measure, given the unsuitability of the WHO functional class due to its narrow range and poor interrater agreement and the limitations of the 6MWT as a surrogate for survival.

It will now be important to assess the predictive value of clinically relevant improvements in HRQoL parameters and their response to intervention, the researchers conclude.

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