SERUM COMPLEMENT DETERMINATIONS IN PATIENTS WITH QUIESCENT SYSTEMIC LUPUS-ERYTHEMATOSUS

Objective. To determine whether complement component analyses during a period of inactive disease can define clinically important subgroups and predict morbidity in patients with systemic lupus erythematosus (S LE). Methods, We identified 277 patients with SLE whose disease became clinically inactive at some point after diagnosis. Serum samples were obtained at that time and tested for total complement activity (CH100 ) and antigenic levels of Clq, Clr, Cia, C3, and C4. Results of comple ment determinations were correlated with demographic characteristics a nd clinical findings in the followup period (mean observation period 4 .25 years). Results, We identified 25 (9%) patients with multiple comp lement determinations below the normal range. 24 other patients (8.5%) had a very low level of a single complement component. The group with multiple complement determinations below the normal range was much mo re likely than the normocomplementemic SLE controls to progress to ren al insufficiency. In other respects, complement component determinatio ns were neither reflective nor predictive of clinical course. Conclusi on, In this group of patients with inactive SLE, complement component analyses did not generally correlate with longterm outcome; however, m ultiple low complement component determinations during disease quiesce nce was associated with increased risk of renal insufficiency.