Table 1.

Definition of kidney outcome, of indications to second biopsy and of histological score

Definition of kidney events
KFI	Decrease in eGFR ≥30% confirmed by at least three determinations for at least 3 months
Proteinuric flare21	Increase in proteinuria without modification of serum creatinine of at least 2 g/24 hours if the previous proteinuria was <3.5 g/24 hours or doubling if previous proteinuria was ≥3.5 g/24 hours
Nephritic flare21	Increase in serum creatinine of at least 30% over the last value, associated with nephritic urinary sediment, with or without increased proteinuria
Arterial hypertension	Systolic blood pressure >140 mm Hg and/or diastolic blood pressure >90 mm Hg in sitting position (mean of three consecutive measurements)
Complete kidney response	Proteinuria<0.5 g/24 hours, normal or near normal eGFR (within 10% of normal eGFR of previously abnormal)
No complete kidney response	All the other cases
Histological assessment
Light microscopy	Specimen fixed in 5% formalin Stains used: H&E, periodic acid-Schiff, silver methenamine and Masson’s trichrome/AFOG
	0	1+	2+	3+
Neutrophil infiltration/karyorrhexis Endocapillary hypercellularity Hyaline deposits Cellular/fibrocellular crescents Fibrous crescents Fibrinoid necrosis Glomerular sclerosis	Absent	Mild (<25% of glomeruli)	Moderate (25%–50% of glomeruli)	Severe (>50% of glomeruli)
Interstitial inflammation Interstitial fibrosis Tubular atrophy	Absent	Mild (<25% of the cortex)	Moderate (25%–50% of the cortex)	Severe (>50% of the cortex)

AFOG, Acid Fuchsin Orange G; eGFR, estimated glomerular filtration rate; KFI, kidney function impairment.