Nephrotic range proteinuria--a good predictive index of disease in IgA nephropathy?

A combined retrospective and prospective study of 86 patients with IgA nephropathy was conducted to determine whether the level of proteinuria was a good predictive index of progressive disease. The patients fell into three groups: Group A, 31 patients with proteinuria of less than 1 g/day, Group B, 31 patients with proteinuria of 1 to 3.5 g/day; and Group C, 24 patients with proteinuria of more than 3.5 g/day. The groups are comparable in age of presentation, sex ratio, and duration of study and showed no difference in serum creatinine levels, creatinine clearance, incidence of hypertension or incidence of impaired renal function. Compared with the patients in the other groups, those in Group C did not have increased incidence of progressive disease. Nevertheless, they have a higher incidence of nephrotic syndrome (p less than 0.001), a lower incidence of macroscopic haematuria (p less than 0.05), lower serum albumin (p less than 0.05) and heavier proteinuria (p less than 0.01). Severity of proteinuria had no significant correlation with the severity of renal histopathologic changes. Clinical observations divided the 24 patients with nephrotic range proteinuria into three well-defined groups with different prognoses. Six patients had progressive disease with decreasing proteinuria. Five of these remained hypertensive and their initial renal biopsy showed advanced pathologic changes. Thirteen patients had persistent proteinuria although the renal function remained unchanged. Three of these were treated with steroid but failed to respond, and their renal histopathologic changes were usually moderate. The remaining five patients showed good response to steroid treatment although two became steroid-dependent. Their renal histopathology showed mild alteration. Our findings suggest that severe proteinuria in IgA nephropathy does not inevitably indicate a poor prognosis.