Urinalysis
Before renal biopsy, the first morning specimen of midstream
urine was collected. Urinalysis was carried out within 2 h of
micturition. Whenever possible, three urine samples collected
on three separate days before the renal biopsy were analyzed to
increase the sensitivity13. The number of samples ranged
between one and three, depending on the waiting period for the
renal biopsy. There were some patients with less than three
urine samples whose urine RBCs increased by less than twofold
vs prebiopsy. Their results of erythrocyte morphology after
biopsy after more than 1 week were included. The urine samples
had to be collected before treatment of the renal pathology.
Urinary erythrocyte morphology was examined by a single
specially trained professional technologist who was experienced
(i.e., who carried out more than 600 urine sediment examinations
per month). First, 10 mL of urine were centrifuged
(377.33 g, 10 min). Then, 9.5 mL of the supernatant were discarded.
The sediment was resuspended in 0.5 mL of urine.
Next, the suspension (20 lL) was investigated in a Fuchs–Rosenthal
counting chamber by phase-contrast microscopy. If a
patient had provided only one urine sample, the results of a
routine urine test from the hospital’s clinical laboratory were
used. Hematuria was defined as >3 RBCs per high-power field
(hpf) in at least two urine samples14,15. Quantitative threshold
values of RBCs have been used as a basis for diagnosis. If
>80% dysmorphic erythrocytes were seen, glomerular hematuria
was diagnosed16–19.