Incidence of biopsy-proven glomerulonephritis

Background. The reported biopsy-proven glomerulonephritis incidence varies according to population characteristics, the unknown true glomerulonephritis incidence and biopsy rate. Reported glomerulonephritis incidence should be evaluated against the biopsy rate. Methods. We report here the glomerulonephritis incidence in our University Hospital (UH) consecutive biopsy material. It is compared to those from surrounding central hospitals (CH), previous single-centre studies and European biopsy registries (EBR). Biopsy rate, when reported, has been considered. Results. The annual biopsy rate/10 5 , median (min-max), at the UHs was 25.4 (15.6-35.1). At the CHs it was 8.7 (5.1-12.6). In previous single-centre studies it has been 18.7-21.5. In the EBRs it has been between 1.0 and 6.9 when reported. The annual incidences (median, min-max) per 10 5 (1980-2000) at the UH were as follows: proliferative glomerulonephritis (9.5, 6.8-18.1), non-proliferative glomerulonephritis (6.7, 3.4-12.6), the four major glomerulonephritis groups MesGN (7.7, 4.4-15.9), ECGN/FPGN-complex (1.4, 0.5-3.2), MCGP/ FSGS-complex (0.9, 0.2-2.7) and MGN (1.4, 0.5-2.4) these which findings were compatible with the single-centre studies and higher than those of the CHs and in the EBRs. Biopsy rate had a major impact on the annual glomerulonephritis incidences explaining 60% of the variation. The relative frequency of MesGN was the highest by all observers, followed by the ECGN/FPGN-complex, MGN and MCGP/ FSGS-complex whose frequencies did not differ much. For every patient commencing renal replacement therapy (Finnish Renal Replacement Registry Data) due to glomerulonephritis there were about 11 subjects with biopsy-proven glomerulonephritis, a relationship compatible with previous reports. Conclusions. The incidence of any glomerulonephritis of 17.6 per 10 5 population was comparable to those from the single-centre studies, but higher than in European biopsy registries, a fact largely explained by biopsy rates.