Primary glomerulonephritis (PGN), is one of the leading cause of end-stage renal failure in western countries including Italy (McGrogan A-2011 , Schena FP and 1997  (full text)). Publications from several renal biopsy databases have reported that PGN is present in approximately half of all native renal biopsies; however, there is a remarkable geographic and temporal variability in the typology/distribution of this complex disease (Zhou FD and 2009  (full text), Braden GL and 2000 , Hanko JB and 2009  (full text)). Consequently, the development of national/regional registers may help clinicians and researchers to improve knowledge about this important clinical condition.
Aim of the study
Therefore, to better assess the Italian PGN distribution and to define whether there has been a progressive reduction of PGN frequency, we decided to take a look to the incidence of this disease in our large north-eastern Italian area in an extensive period (from 1998 to 2010).
A record of 4378 adult patients (aged>18 years old, male: 2719, female: 1659, mean patients age: 50.4±17.7 years) with native kidney biopsies performed, from 01 January 1998 to 31 December 2010, in a large north-eastern Italian area (including: Veneto, Friuli Venezia Giulia and Trentino Alto Adige regions; comprising approximately 5 millions inhabitants) were retrospectively analyzed.
– The overall clinical indications to perform renal biopsy were: nephrotic syndrome (NS), chronic renal failure (CRF), urinary abnormalities (UA), acute renal failure (ARF), macroscopic hematuria (MH) and nephritic syndrome (NeS).
– Kidney diseases were divided in 5 groups: PGN, secondary glomerulonephrities (SGN), tubulo-interstitial nephritis (TIN), vascular diseases and miscellaneous. For our study, we focused on PGN.
– For all patients, demographic, clinical and renal histopathological characteristics were included in the “Triveneto” Register of Renal Biopsies (TVRRB). Biopsies have been evaluated with light microscopy (100%), immunofluorescence (70%), and electron microscopy (40%) using standard diagnostic criteria.
– Data recorded in the TVRRB were exported and stored in a standard database. Pearson’s correlation test was used to measure changes of all demographic and clinical variables during the study period. P-values<0.05 were considered to be statistically significant. R 2.0.1 statistical software was used to perform the statistical analyses.
Demographic features of patients with PGN
From January 1998 to December 2010, 4378 qualified renal biopsies were identified, and 2680 (61.2%) patients were diagnosed as PGN. Other diagnoses were: secondary glomerulonephritis (n=1023, 23.4%), tubular-interstitial nephropathy (n=240, 5.5%), vascular renal disease (n=183, 4.2%) and other causes (n=252, 5.7%). For our analysis, we focused only on PGNs.
As showed in FIGURE 1, we did not found any significant difference in the annual incidence rate of kidney biopsy for all causes (Total, p=0.25) and for PGN (p=0.56) during the study period. Interestingly, we found a significant and progressive increase from 1998 to 2010 in the annual average age of PGN patients (R2=0.82, p<0.01) with a constant predominance of male on female (FIGURE 2A and 2C). Additionally, data analysis showed a significant increment of the proportion of elderly PGN patients (> 65 years old) overtime (R2=0.72, p<0.01) (FIGURE 2B).
Clinical presentations of PGN
During the study period, we observed a statistically significant increment of the number/percentage of PGN patients biopsied for ARF (p<0.01) and a decrease in those for NeS (p=0.04) and MH (p<0.01). On the other hands, the number of patients with PGN and CRF, NS, and UA as clinical presentation did not changed during the study period (TABLE 1).
Incidence of biopsy-proven PGN
The leading types of PGN were: IgAN followed by MGN and FSGS. Interestingly, although the overall number of biopsy-proven PGN has been substantially constant during the study period, we found a significant enhancement of MCD (p=0.04) and extracapillary proliferative GN (p=0.03) incidence over time. Occurrence of IgAN (p=0.63), MGN (p=0.10), FSGS (p=0.14), MesGN (p=0.29), MPGN (p=0.37) and AGN (p=0.70) was unchanged during the study period (TABLE 2).
in our large study area the number of PGN is not diminished during the 13 years study period. However, the maintenance of a constant number of PGN seems not be related to an enhancement of emerging histopathological patterns as FSGS, but to other forms such as ExGN and MCD. This may reflects not only an enhancement of our nephrology patients age, but also a progressive change of our hospitals biopsy policy.