Serum Complement C3 and C4 Levels in Relation to Diagnosis of Lupus Nephritis

Purpose: The main objective of this study was to measure serum complement C3 and C4 concentrations in patients of lupus nephritis to see if these simple measurements would give useful information to the clinician managing such patients.. Method: A total of 52 samples were obtained from SLE patients, 17 suffering from lupus nephritis. All patients met the revised 1997 American College of Rheumatology criteria for SLE. Serum C3 and C4 concentrations were measured with single gel radioimmunodiffusion technique. Results: In lupus nephritis, C3 and C4 are generally correlated. Both C3 and C4 levels were decreased but C4 concentrations were more often and more profoundly depressed than C3 concentration. Conclusion: All patients of lupus nephritis with low C3 or C4 concentrations should have serial measurements performed and selected patients will need a full complement profile, including measurement of alternate pathway components and total hemolytic pathway.