Introduction: The possible confounding influence of investigator-related preferences, available histological techniques, and healthcare systems on the frequencies and incidences of primary and secondary nephropathies was evaluated in this long-term observation.
Materials and methods: The observation time from 1983 to 2010 was divided in regard to the political regimes: a) prior to and after German reunification: German Democratic Republic (GDR, period 1 from 1983 to 1990)/Federal Republic of Germany (FRG, period 2 from 1990 to 2010); and the two heads of the division of nephrology, b) conductor 1 (1983 - 2006) and conductor 2 (2006 - 2010). 467 kidney biopsies at the University Hospital of Leipzig were included in our analysis.
Results: In period 1, due to the unavailability of immunofluorescence methods, mesangioproliferative glomerulonephritis (MesP) was the most dominating nephropathy. In period 2, IgA nephropathy (IgAN) was the most common nephropathy (17%). IgAN was followed by crescentic glomerulonephritis (13%), hypertensive nephropathy (10%), minimal-change disease, and membranous glomerulonephritis (each 9%). From period 1 to period 2, MesP/IgAN (62% to 16%), membranoproliferative glomerulonephritis and postinfectious glomerulonephritis decreased significantly (p < 0.05). IgAN decreased significantly (p < 0.05) from conductor 1 to conductor 2 (21% to 6%), while diabetic nephropathy significantly increased. Focal-segmental glomerulosclerosis (FSGS) had the highest incidence rate with 1.0, followed by IgAN with 0.8 (per 100,000 per year).
Conclusion: In a nearly ethnically identical cohort, we have demonstrated that confounding factors, e.g., healthcare systems and preferences of conductors, have a strong influence - more than 10-fold variance - on frequency and incidence on the spectrum of nephropathies. .