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Pattern of proteinuria in IgA nephritis by SDS-PAGE: clinical significance
1Department of Renal Medicine, Singapore General Hospital, Republic of Singapore.
Insights
In IgA nephritis patients, specific protein patterns in urine, especially low molecular weight (LMW) proteinuria, predict a higher risk of developing chronic renal failure (CRF). SDS-PAGE analysis offers a better prognosis than traditional indices.
Area of Science:
- Nephrology
- Immunology
Background:
- Immunoglobulin A (IgA) nephritis is a common cause of glomerulonephritis.
- Chronic renal failure (CRF) is a significant complication of IgA nephritis.
- Proteinuria patterns may indicate disease progression.
Purpose of the Study:
- To investigate the prognostic value of different proteinuria patterns in IgA nephritis.
- To compare the predictive power of SDS-PAGE analysis with traditional indices like GSI and SI.
Main Methods:
- Sixty patients with IgA nephritis were followed for six years.
- Proteinuria was analyzed using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE).
- Patients were categorized into four proteinuria patterns based on molecular weight (MW).
Main Results:
- Patients with mixed proteinuria (patterns 2, 3, 4) had a higher incidence of CRF (38%) compared to those with only middle molecular weight (MMW) proteinuria (pattern 1) (6%).
- Low molecular weight (LMW) proteinuria was associated with a significantly higher incidence of CRF (47%) versus those without (10%).
- SDS-PAGE proteinuria patterns were better predictors of CRF than Glomerular Selectivity Index (GSI) or Selectivity Index (SI).
Conclusions:
- The pattern of proteinuria, particularly the presence of LMW proteinuria, is a strong indicator of poor prognosis in IgA nephritis.
- SDS-PAGE analysis of proteinuria provides a more effective prognostic tool for IgA nephritis than GSI or SI.
Abstract:
Of sixty patients with IgA nephritis, none had CRF at first examination, 13 developed CRF with creatinine above 1.6 mg/dl within 6 years. Among these patients who had analysis of proteinuria by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), 31 patients had middle molecular weight (MMW) proteinuria alone (pattern 1), 10 had MMW and Low MW (LMW) or tubular proteinuria (pattern 2), 10 had high MW (HMW) and MMW proteinuria (Pattern 3) and 9 had HMW, MMW and LMW proteinuria (Pattern 4). At the end of a follow up period of 6 years (1983-1989) patients with mixed proteinuria had a higher incidence of chronic renal failure (CRF), 11/29 (38%) compared to those with pattern 1 proteinuria, 2/31 (6%) (chi 2 = 8.7, p less than 0.005). Based on the glomerular selectivity index (GSI), 19 patients had nonselective proteinuria but they did not have a higher incidence of CRF. By the selectivity index (SI), 18 patients had nonselective proteinuria and they showed a significantly higher incidence of CRF. Compared to the 41 patients who did not have LMW proteinuria, 19 patients with LMW proteinuria had more severe proteinuria. After a follow-up period of 6 years, patients with LMW proteinuria had a higher incidence of CRF (10% versus 47%, p less than 0.001). The presence of LMW proteinuria indicates a less favourable outcome and the pattern of proteinuria as assessed by the SDS-PAGE appears to be a better prognostic index in IgA nephritis than the SI and the GSI.