A Novel Discriminant Function in the Diagnosis of IgA Nephropathy

Kim, Dong Lyul; Kim, Think You

Abstract

BACKGROUND
IgA nephropathy is characterized by showing a prominent mesangial deposition of IgA in biopsy specimens. More than 20% of these patients progress to an end-stage renal disease over a period of 20 years. However, it is difficult to perform renal biopsies in all patients who present with hematuria or proteinuria. The present study was undertaken to determine whether discriminant analysis before renal biopsy is useful in the diagnosis of IgA nephropathy.
METHODS
A total of 144 patients who were diagnosed by renal biopsy were analyzed. This group of 144 patients included 76 patients who had an IgA nephropathy, and did not include those patients that had systemic lupus erythematosus, Henoch-Schonlein purpura or other systemic diseases, and 68 patients with a different kind of primary chronic glomerulonephritis. Discriminant analysis was used to clearly demarcate these two groups by using 20 clinical variables.
RESULTS
Among the 20 clinical variables, the levels of serum albumin, serum IgG, serum IgA, the degree and quantitation of proteinuria, the degree of microhematuria, and the RBC counts of the urinary sediments in the IgA nephropathy group were significantly higher than those in the non-IgA nephropathy group. Also, the presence of subjective symptoms was significantly different between the two groups. Using the stepwise method, serum albumin (ALB), serum IgA (IGA), and the degree of microhematuria (MICRO) were chosen to be the discriminant markers and resulted in a correct classification rate of 81.3%. The discriminant function (D) was 'D=0.842XALB+0.523XIGA+0.414XMICRO'.
CONCLUSIONS
It was considered that discriminant analysis using clinical markers such as serum albumin, serum IgA, and degree of microhematuria before renal biopsy is useful in the clinical diagnosis of IgA nephropathy.