RESPIRATORY-FUNCTION IN SYSTEMIC LUPUS-ERYTHEMATOSUS - RELATION WITH ACTIVITY AND SEVERITY

The objective of this study was to examine the relation between respir atory function tests, disease activity and disease severity in ambulat ory patients with systemic lupus erythematosus (SLE) who did not prese nt with overt respiratory problems. Lung volumes, maximal expiratory f lows at 50% and 25% of vital capacity (MEF(50) and MEF(25)), bronchial threshold to methacholine (PD(15)FEV(1)), transfer factor CO (KCO) we re measured in 24 consecutive SLE outpatients (22 women, age 41 +/- 14 .8 years) and in 24 healthy controls matched for age and sex. In SLE p atients alveolar-arterial oxygen gradient (AaO(2)) was also measured. Disease activity was assessed by European Consensus Lupus Activity Mea surement (ECLAM) scoring system and disease severity by Lupus Severity of Disease Index. In comparison to controls SLE patients showed a sig nificant decrease of total lung capacity (TLC) (91.7 +/- 16.5 vs 102.7 +/- 12.9% predicted, P < 0.01), MEF(25) (58.4 +/- 25.2 vs 73.5 +/- 19 .5% predicted, P < 0.005), PD(15)FEV(1) (2164 +/- 1122 lis 4230 +/- 10 14 mu g methacholine, P < 0.0001) and KCO (77.1 +/- 20.5 vs 96.3 +/- 1 2.4% predicted, P < 0.001). AaO(2) (mean value 13.2 +/- 8.4) was abnor mally high (>20 mm Hg) in 12 patients. The ECLAM score of activity was inversely related with KCO (r = 0.48, P < 0.02). The severity index w as significantly related with FEV,NC ratio (r = 0.43, P < 0.05), MEF(5 0) (r = 0.51, P < 0.01), MEF(25) (r = 0.40, P < 0.05) and PD(15)FEV(1) (r = 0.51, P < 0.01). In eight patients, evaluated also after treatme nt intensification, there was a significant increase in KCO (from 71.8 +/- 24.7 to 84.9 +/- 22.3% predicted, P < 0.01) along with a decrease in ECLAM score (from 3.0 +/- 1.34 to 0.69 +/- 0.75, P < 0.01). The re lation between disease activity and KCO suggests a relation between sy stemic and alveolar inflammation whereas the relation between severity index, airway patency and reactivity indices suggests a cumulative da mage to the airways in SLE patients, even in the absence of overt resp iratory manifestations.