Objective: To determine the effects of lung involvement on respiratory function in patients with ANCA-associated vasculitis and the relation to impaired health status.
Methods: Thirty patients with ANCA-associated vasculitis in remission (15 with lung involvement at diagnosis as determined by an abnormal chest X-ray) were examined. We measured lung function, skeletal muscle strength [quadriceps force (QF), respiratory muscle strength (Pi(max))], exercise capacity (VO(2) peak) using treadmill exercise tests, and health status using the Short Form 36 and St George's respiratory questionnaires.
Results: Exercise capacity was reduced compared with predicted values (58.2%, range 23-123%) and 18 patients showed functional aerobic impairment. Respiratory muscle function was reduced (72.1% predicted, range 20-108%) and was not related to lung involvement or steroid usage. Transfer factor correlated significantly with exercise capacity, suggesting inadequate delivery of oxygen to muscles. Nine patients had reduced transfer factor (seven with lung involvement). Patients with lung involvement had impaired gas transfer compared with those without lung involvement (96.9 +/- 6 vs 113.3 +/- 4.7% predicted, P = 0.04). However, there were significant abnormalities in other lung function parameters not related to previous lung involvement (eight patients had reduced forced expiratory volume in 1 s, and five patients had reduced residual volume). Twelve patients (five with previous lung involvement) had obstructive airways disease. Physical health status was impaired to a greater degree than mental health status across the whole group and was not related to lung involvement or original disease severity, but correlated with transfer factor.
Conclusion: Patients with ANCA-associated disease may have significant lung function impairment irrespective of lung involvement at the time of diagnosis. Patients showed reduced respiratory muscle strength, health status and exercise capacity, which correlated with reduced transfer factor.