Investigators followed 604 COPD patients with predominantly severe or very severe disease who were prospectively followed-up from their first full lung function testing. Over a median follow-up of 83.1 months, 37.9% of the patients died. Significant differences between the baseline clinical characteristics of those patients and survivors were identified; among the factors were age, BMI, a likelihood of being in GOLD stage 4, and an increased likelihood of being on long-term oxygen therapy.
However, investigators noted that those who died, when compared to survivors, also had reduced FEV1, lower carbon monoxide transfer factor (TLCO), lower arterial oxygen partial pressure, and higher functional residual capacity.
“In a large, general COPD outpatient population where a complete range of lung function testing had been applied, gas transfer provided the best prediction of survival, together with age and PaO2,” the authors concluded.
“Spirometry, although easy to perform and low-cost, cannot offer as much information as gas transfer, which is also superior to plethysmographic lung volume measurements. An argument can therefore be made for performing measures of gas transfer in routine practice for patients with COPD to provide them with the best prognostic information, and future classifications of COPD should include TLCO and not rely merely on the severity of airflow obstruction,” they wrote.