General data of patients
The detailed general clinic-pathological data of the patients were shown in Table 1 and Supplementary Table 1. Of the 126 patients included in the analysis, 92 patients with proliferative lupus nephritis, and 34 patients with endocapillary proliferative IgA nephropathy.
Table 1
Clinical data of patients with endocapillary proliferative glomerulonephritis
| All patients n = 126 | Patients with LN n = 92 | Patients with IgAN n = 34 |
Gender (male/female) | 41/85 | 24/68 | 17/17 |
Age (mean ± s.d.) (years) | 35.84 ± 16.00 | 33.92 ± 14.13 | 41.03 ± 19.50 |
Acute kidney injury no. (%) | 37(29.37%) | 28(30.43%) | 9(26.47%) |
Urine protein (median, IQR) (g/24 h) | 4.42;2.79–7.71 | 4.53;2.88–7.42 | 4.21;2.50–9.01 |
Serum creatinine (median, IQR) (umol/l) | 99.1;75.5-176.3 | 107.1;78.9-179.3 | 80.1;69.5-129.7 |
eGFR (mean ± s.d.) (ml/min per 1.73 m2) | 67.33 ± 37.78 | 62.70 ± 35.18 | 79.85 ± 42.08 |
Serum C3 (mean ± s.d.) (g/l) | 0.49 ± 0.31 | 0.35 ± 0.14 | 0.85 ± 0.33 |
Serum IgA (median, IQR) (g/l) | | | 2.60;1.71–4.44 |
SLEDAI (median, IQR) | | 21;19–24 | |
Antinuclear antibody (+) no. (%) | | 91(98.91%) | |
Anti-dsDNA antibody (+) no. (%) | | 80(86.96%) | |
Anti-cardiolipin antibody (+) no. (%) | | 4(4.35%) | |
LN lupus nephritis, IgAN IgA nephropathy, IQR interquartile range, SLEDAI Systemic Lupus Erythematosus Disease Activity Index, dsDNA double-stranded DNA |
In the proliferative lupus nephritis group, 24 (26.1%) were male and 68 (73.9%) female, with a mean age of 33.92 ± 14.13 years. At the time of renal biopsy, the median proteinuria was 4.53 (IQR 2.88–7.42) g/24 hours, and the average estimated glomerular filtration rate (eGFR) was 62.70 ± 35.18 ml/min per 1.73 m2. According to the 2003 ISN/RPS classification system of lupus nephritis, all patients were classified as class IV (100%, including 21 as class IV + V).
The mean age of the patients with endocapillary proliferative IgA nephropathy was 41.03 ± 19.50 years and the male-to-female ratio was 1:1. At the time of renal biopsy, the median proteinuria was 4.21 (IQR 2.50–9.01) g/24 hours, and the mean eGFR was 79.85 ± 42.08 ml/min per 1.73 m2. The pathological lesions of IgA nephropathy patients were graded using the Oxford classification (MESTC scores). Mesangial hypercellularity (M1), endocapillary hypercellularity (E1), and segmental glomerulosclerosis (S1) were found in 34 (100%), 34 (100%), and 9 (26.5%) patients, respectively. For tubular atrophy and interstitial fibrosis (Oxford-T) and crescent (Oxford-C) lesions, T0, T1, and T2 were found in 17(50.0%), 15 (44.1%), and 2 (5.9%) patients, while C0, C1, and C2 were found in 4 (11.8%), 12(35.3%), and 18(52.9%) patients.
Comparisons of urine sediment between patients with proliferative lupus nephritis and patients with endocapillary proliferative IgA nephropathy
The severity of microscopic hematuria and leukocyturia were defined according to the IQR of all the patients. In the patients with endocapillary proliferative glomerulonephritis, normal to mild hematuria (≤ 35/HPF), and moderate to severe hematuria (> 35/HPF) were found in 31(24.60%) and 95 (75.40%) patients, respectively; normal to mild leukocyturia (≤ 12/HPF), and moderate to severe leukocyturia (> 12/HPF) were found in 52(41.27%) and 74 (58.73%) patients, respectively. The frequency of different types of urinary casts were shown in Table 2.
Table 2
Comparisons of urine sediment between patients with proliferative lupus nephritis and patients with endocapillary proliferative IgA nephropathy
| All enrolled patients n = 126 | Patients with lupus nephritis n = 92 | Patients with IgA nephropathy n = 34 | P-value |
Erythrocytes, HPF | | | | 0.525 |
Normal to mild, ≤ 35/HPF No. (%) | 31(24.60%) | 24(26.09%) | 7(20.59%) | |
Moderate to severe, > 35/HPF No. (%) | 95(75.40%) | 68(73.91%) | 27(79.41%) | |
Leukocytes, HPF | | | | < 0.001 |
Normal to mild, ≤ 12/HPF No. (%) | 52(41.27%) | 29(31.52%) | 23(67.65%) | |
Moderate to severe, > 12 /HPF No. (%) | 74(58.73%) | 63(68.48%) | 11(32.35%) | |
Renal tubular epithelial cells, HPF No. (%) | 33(26.19%) | 21(22.82%) | 12(35.29%) | 0.158 |
Lipid droplets, HPF No. (%) | 32(25.40%) | 18(19.57%) | 14(41.18%) | 0.013 |
Hyaline casts, LPF No. (%) | 101(80.16%) | 73(79.35%) | 28(82.35%) | 0.707 |
Granular casts, LPF No. (%) | 64(50.79%) | 50(54.35%) | 14(41.18%) | 0.189 |
Red blood cells casts, LPF No. (%) | 60(47.62%) | 45(48.91%) | 15(44.12%) | 0.632 |
White blood cells casts, LPF No. (%) | 66(52.38%) | 54(58.70%) | 12(35.29%) | 0.020 |
Epithelial cells casts, LPF No. (%) | 38(30.16%) | 26(28.26%) | 12(35.29%) | 0.445 |
Mixed cellular casts, LPF No. (%) | 57(45.24%) | 45(48.91%) | 12(35.29%) | 0.173 |
Lipid laden casts, LPF No. (%) | 23(18.25%) | 12(13.04%) | 11(32.35%) | 0.013 |
Waxy casts, LPF No. (%) | 45(35.71%) | 39(42.39%) | 6(17.65%) | 0.010 |
HPF high-power field, LPF low-power field |
P value was used to indicate the difference between the patients with lupus nephritis and the patients with IgA nephropathy. A two-tailed P < 0.05 was considered statistically significant |
There was no significant difference of the microscopic hematuria between patients with proliferative lupus nephritis and patients with endocapillary proliferative IgA nephropathy. The proportion of normal to mild leukocyturia (≤ 12/HPF) in patients with proliferative lupus nephritis were significantly lower than that in the patients with endocapillary proliferative IgA nephropathy (29(31.52%) versus 23(67.65%), P < 0.001), whereas the proportion of moderate to severe (> 12/HPF) leukocyturia in lupus nephritis group were significantly higher than that in IgA nephropathy group (63(68.48%) versus 11(32.35%), P < 0.001) (shown in Fig. 1A, 1B). Urinary leukocytes were classified in 19 patients with proliferative lupus nephritis, polymorphonuclear leukocytes > 50%, and mononuclear leukocytes > 50% were found in 14 (73.78%), and 5 (26.32%) patients, respectively. In addition, the frequency of urinary WBC casts (shown in Fig. 1C) and waxy casts (shown in Fig. 1D) were significantly higher in proliferative lupus nephritis patients compared with endocapillary proliferative IgA nephropathy patients (54(58.70%) versus 12(35.29%), P = 0.020; 39(42.39%) versus 6(17.65%), P = 0.010, respectively), whereas the frequency of urinary lipid droplets and lipid laden casts were significantly lower in proliferative lupus nephritis patients compared with endocapillary proliferative IgA nephropathy patients (18(19.57%) versus 14(41.18%), P = 0.013; 12(13.04%) versus 11(32.35%), P = 0.013, respectively). No significant differences were found of the other types of urinary casts (hyaline casts, granular casts, RBC casts, epithelial cells casts, and mixed cellular casts) between the two groups (Table 2).
Correlation analysis of leukocyturia with clinicopathological data in endocapillary proliferative glomerulonephritis
Of the patients with endocapillary proliferative glomerulonephritis, the levels of leukocyturia were significantly correlated with serum albumin (r=-0.206, P = 0.021), serum creatinine (r = 0.275, P = 0.002), eGFR (r=-0.233, P = 0.009) and serum C3 (r=-0.351, P < 0.001). In terms of renal pathological data, it was found that leukocyturia was positively correlated with glomerular leukocyte infiltration (r = 0.294, P = 0.001) (Table 3).
Table 3
Correlation analysis of leukocyturia with clinicopathological data in endocapillary proliferative glomerulonephritis
| All patients n = 126 r value P value | Patients with LN n = 92 r value P value | Patients with IgAN n = 34 r value P value |
Clinical data | | | |
Age (years) | -0.298 0.001 | -0.168 0.109 | -0.458 0.007 |
Albumin (g/l) | -0.206 0.021 | -0.015 0.886 | -0.292 0.094 |
Urine protein (g/24 h) | 0.072 0.425 | 0.044 0.684 | 0.208 0.237 |
Serum creatinine (µmol/l) | 0.275 0.002 | 0.288 0.005 | 0.070 0.694 |
eGFR (ml/min per 1.73 m2) | -0.233 0.009 | -0.284 0.006 | 0.123 0.488 |
C3 (g/l) | -0.351 ༜0.001 | -0.275 0.009 | 0.036 0.840 |
SLEDAI | | 0.383 ༜0.001 | |
Renal histopathology indices | | | |
Crescents /Cellular crescents/ Oxford-C | 0.102 0.724 | 0.177 0.470 | 0.204 0.829 |
Interstitial inflammatory cell infiltration | 0.114 0.652 | 0.188 0.374 | 0.291 0.411 |
Glomerular leukocyte infiltration | 0.294 0.001 | 0.285 0.002 | 0.266 0.568 |
Activity indices (AIs) score | | 0.171 0.114 | |
Chronicity indices (CIs) score | | -0.097 0.369 | |
Oxford-S | | | 0.304 0.398 |
Oxford-T | | | 0.301 0.447 |
LN lupus nephritis, IgAN IgA nephropathy, SLEDAI Systemic Lupus Erythematosus Disease Activity Index |
S glomerulosclerosis, T tubular atrophy and interstitial fibrosis, C cellular or fibrocellular crescents |
A two-tailed P < 0.05 was considered statistically significant |
In the proliferative lupus nephritis group, the levels of leukocyturia was significantly correlated with serum creatinine (r = 0.288, P = 0.005), eGFR (r=-0.284, P = 0.006), serum C3 (r=-0.275, P = 0.009) and SLEDAI scores (r = 0.383, P < 0.001). In terms of renal pathological data, leukocyturia was positively associated with glomerular leukocyte infiltration (r = 0.285, P = 0.002) (Table 3).
There was a negative correlation between leukocyturia and age at kidney biopsy (r=-0.458, P = 0.007) in endocapillary proliferative IgA nephropathy. No correlations were found between the leukocyturia and other clinicopathological parameters (Table 3).
Comparisons of clinicopathological data between patients with leukocyturia and patients without leukocyturia
Patients with leukocyturia presented with significantly higher frequency of granular casts, WBC casts and waxy casts compared with those without (59(59.60) versus 5(18.52), P < 0.001; 61(61.62) versus 5(18.52), P < 0.001; 40(40.40) versus 5(18.52), P = 0.04, respectively).The serum levels of albumin and C3 was significantly lower in the patients with leukocyturia than that in the patients without leukocyturia (25.1 ± 5.9 versus 28.3 ± 6.1 g/l, P = 0.02; 0.46 ± 0.28 versus 0.61 ± 0.36 g/l, P = 0.02, respectively). The prevalence of glomerular leukocyte infiltration was significantly higher in the patients with leukocyturia compared with those without (88(88.89%) versus 17(62.96%), P = 0.004) (Table 4).
Table 4
Comparisons of clinicopathological data between patients with leukocyturia and patients without leukocyturia
| All patients (n = 126) Lkc (-) Lkc (+) P value | Patients with LN (n = 92) Lkc (-) Lkc (+) P value | Patients with IgAN (n = 34) Lkc (-) Lkc (+) P value |
Urine sediment no. (%) | | | | | | | | | |
Erythrocytes (moderate to severe) | 18(66.67) | 77(77.78) | 0.24 | 9(64.29) | 59(75.64) | 0.58 | 9(69.23) | 18(85.71) | 0.47 |
Renal tubular epithelial cells | 6(22.22) | 27(27.27) | 0.60 | 2(14.29) | 19(24.36) | 0.63 | 4(30.77) | 8(38.10) | 0.95 |
Lipid droplets | 3(11.11) | 29(29.29) | 0.05 | 0(0.00) | 18(23.08) | 0.10 | 3(23.08) | 11(52.38) | 0.09 |
Hyaline casts | 21(77.78) | 80(80.81) | 0.73 | 9(64.29) | 64(82.05) | 0.25 | 12(92.31) | 16(76.19) | 0.46 |
Granular casts | 5(18.52) | 59(59.60) ༜0.001 | 2(14.29) | 48(61.54) | 0.001 | 3(23.08) | 11(52.38) | 0.09 |
Red blood cells casts | 9(33.33) | 51(51.52) | 0.09 | 5(35.71) | 40(51.28) | 0.28 | 4(30.77) | 11(52.38) | 0.22 |
White blood cells casts | 5(18.52) | 61(61.62) ༜0.001 | 3(21.43) | 51(65.38) | 0.002 | 2(15.38) | 10(47.62) | 0.12 |
Epithelial cells casts | 8(29.63) | 30(30.30) | 0.95 | 5(35.71) | 21(26.92) | 0.73 | 3(23.08) | 9(42.86) | 0.42 |
Mixed cellular casts | 10(37.04) | 47(47.47) | 0.33 | 6(42.86) | 39(50.00) | 0.62 | 4(30.77) | 8(38.10) | 0.95 |
Fatty casts | 3(11.11) | 20(20.20) | 0.42 | 0(0.00) | 12(15.38) | 0.25 | 3(23.08) | 8(38.10) | 0.59 |
Waxy casts | 5(18.52) | 40(40.40) | 0.04 | 3(21.43) | 36(46.15) | 0.09 | 2(15.38) | 4(19.05) | 0.79 |
Clinical data | | | | | | | | | |
Anemia no. (%) | 20(74.07) | 78(78.79) | 0.60 | 12(85.71) | 66(84.62) | 0.92 | 8(61.54) | 12(57.14) | 0.80 |
Albumin (g/l) (mean ± s.d.) | 28.3 ± 6.1 | 25.1 ± 5.9 | 0.02 | 26.4 ± 5.7 | 24.3 ± 5.4 | 0.18 | 30.3 ± 6.4 | 28.0 ± 6.8 | 0.26 |
Urine protein (g/24 h) (median, IQR) | 3.7(2.6,8.0) | 4.6(2.9,7.8) | 0.41 | 3.6(3.0,7.3) | 4.6(2.6,7.5) | 0.86 | 3.8(2.1,9.5) | 5.8(3.5,8.9) | 0.26 |
Serum creatinine (µmol/l) (median, IQR) | 82(70,124) | 104(77,180) | 0.11 | 102(75,128) | 113(81,189) | 0.22 | 73(66,225) | 82(71,137) | 0.55 |
eGFR (ml/min per 1.73 m2) (mean ± s.d.) | 74.3 ± 38.8 | 65.4 ± 37.5 | 0.28 | 73.1 ± 34.0 | 60.8 ± 35.3 | 0.23 | 75.7 ± 44.8 | 82.4 ± 41.2 | 0.68 |
C3 (g/l) (mean ± s.d.) | 0.61 ± 0.36 | 0.46 ± 0.28 | 0.02 | 0.43 ± 0.14 | 0.34 ± 0.13 | 0.03 | 0.79 ± 0.43 | 0.89 ± 0.26 | 0.38 |
Acute kidney injury no. (%) | 5(18.52) | 32(32.32) | 0.16 | 1(7.14) | 27(34.62) | 0.08 | 4(30.77) | 5(23.81) | 0.96 |
SLEDAI (median, IQR) | | | | 14(11,23) | 22(20,24) | 0.003 | | | |
Renal histopathology indices no. (%) | | | | | | | | | |
Crescents /Cellular crescents/C1-C2 | 22(81.48) | 81(81.82) | 0.97 | 2(0,2) | 2(2,4) | 0.04 | 11(84.62) | 19(90.48) | 0.60 |
Interstitial inflammatory cell infiltration | 26(96.30) | 95(95.96) | 0.94 | 1(1,1) | 1(1,2) | 0.87 | 12(92.31) | 20(95.24) | 0.72 |
Glomerular leukocyte infiltration | 17(62.96) | 88(88.89) | 0.004 | 2(1,2) | 2(1,2) | 0.04 | 4(30.77) | 11(52.38) | 0.22 |
Activity indices (AIs) score | | | | 8(6,8) | 9(7,10) | 0.04 | | | |
Chronicity indices (CIs) score | | | | 2(1,3) | 2(1,2) | 0.48 | | | |
S1 | | | | | | | 5(38.46) | 4(19.05) | 0.40 |
T1-T2 | | | | | | | 7(53.85) | 10(47.62) | 0.72 |
LN lupus nephritis, IgAN IgA nephropathy, Lkc leukocyturia, IQR interquartile range, SLEDAI Systemic Lupus Erythematosus Disease Activity Index |
S1 present segmental glomerulosclerosis, T1-T2 severity of tubular atrophy/interstitial fibrosis (T1 = 26–50%; T2 > 50%), C1-C2 present crescent (C1 = 1–25%; C2 = 26–100%) |
A two-tailed P < 0.05 was considered statistically significant |
In the proliferative lupus nephritis group, the frequency of urinary granular casts and WBC casts were significantly higher in the patients with leukocyturia compared with those without (48(61.54%) versus 2(14.29%), P = 0.001; 51(65.38%) versus 3(21.43%), P = 0.002, respectively). Moreover, the serum C3 levels were significantly lower in the patients with leukocyturia than that in the patients without leukocyturia (0.34 ± 0.13 versus 0.43 ± 0.14 g/l, P = 0.03). SLEDAI scores was significantly higher in the patients with leukocyturia than that in the patients without leukocyturia (22(20,24) versus 14(11,23), P = 0.003). The scores of cellular crescents, glomerular leukocyte infiltration, activity indices were significantly higher in the patients with leukocyturia compared with those without (2(2,4) versus 2(0,2), P = 0.04; 2(1,2) versus 2(1,2), P = 0.04; 9(7,10) versus 8(6,8), P = 0.04, respectively). (Table 4).
In the endocapillary proliferative IgA nephropathy group, no significant clinicopathological difference was found between the patients with leukocyturia and those without leukocyturia.
Association of leukocyturia and renal outcomes in patients with endocapillary proliferative glomerulonephritis
In our study, 56 patients with endocapillary proliferative glomerulonephritis were regularly followed up, with an average follow-up time of 35.7 ± 24.1months. With regard to long-term renal outcomes, 9 patients (9/56, 16.07%) reached the composite end point, defined as ESRD or doubling of serum creatinine levels or 50% eGFR decline. Using the log-rank test for univariate survival analysis, we found that leukocyturia was a risk factor for renal outcome (HR: 1.233, 95% CI: 1.042–1.460, P = 0.015). In the further multivariate Cox hazard analysis, leukocyturia remained as an independent risk factor for renal outcome (HR: 1.519, 95% CI: 1.103–2.091, P = 0.010) (Table 5).
Table 5
Univariate and multivariate analysis of independent prognostic factors for renal survival
All patients | Univariable | Multivariable |
Risk Factor | HR (95% CI) | P value | HR (95% CI) | P value |
Age | 1.033 (0.994 to 1.074) | 0.101 | | |
Gender | 0.134 (0.028 to 0.648) | 0.012 | | |
Proteinuria | 1.086 (0.959 to 1.230) | 1.092 | | |
Serum creatinine | 1.004 (1.002 to 1.006) | < 0.001 | 1.003 (1.000 to 1.006) | 0.030 |
Leukocyturia (non-infection) | 1.233 (1.042 to 1.460) | 0.015 | 1.519 (1.103 to 2.091) | 0.010 |
Crescents | 1.162 (0.691to 1.954) | 0.572 | | |
Glomerular leukocyte infiltration | 0.297 (0.047 to 1.189) | 0.086 | | |
Patients with lupus nephritis | Univariable | Multivariable |
Risk Factor | HR (95% CI) | P value | HR (95% CI) | P value |
Age | 0.999 (0.937 to 1.067) | 0.988 | | |
Gender | 0.182 (0.033 to 0.993) | 0.049 | | |
SLEDAI | 0.987 (0.791 to 1.233) | 0.910 | | |
Acute kidney injury | 1.525 (0.992 to 2.342) | 0.054 | | |
Leukocyturia (non-infection) | 1.463 (1.085 to 1.973) | 0.013 | 1.456(1.083 to 1.957) | 0.013 |
Activity indices score | 1.402 (1.022 to 1.923) | 0.036 | | |
Chronicity indices score | 1.440 (1.036 to 2.000) | 0.030 | | |
Patients with IgA nephropathy | Univariable | Multivariable |
Risk Factor | HR (95% CI) | P value | HR (95% CI) | P value |
Age | 1.062 (0.984 to 1.146) | 0.120 | | |
Gender | 0.460 (0.069 to 3.069) | 0.423 | | |
Urine protein | 1.056 (0.839 to 1.330) | 0.641 | | |
Serum creatinine | 1.020 (0.977 to 1.065) | 0.366 | | |
Leukocyturia (non-infection) | 0.957 (0.823 to 1.112) | 0.562 | 1.069 (0.494 to 2.312) | 0.866 |
S1 | 0.510 (0.046 to 5.611) | 0.582 | | |
T1-T2 | 0.631 (0.056 to 7.060) | 0.709 | | |
C1-C2 | 1.882 (0.492 to 7.198) | 0.356 | | |
HR hazard ratio, 95% CI 95% confidence interval, SLEDAI Systemic Lupus Erythematosus Disease Activity Index |
S1 present segmental glomerulosclerosis, T1-T2 severity of tubular atrophy/interstitial fibrosis (T1 = 26–50%; T2 > 50%), C1-C2 present crescent (C1 = 1–25%; C2 = 26–100%) |
A two-tailed P < 0.05 was considered statistically significant |
In subgroup analysis, 45 patients with proliferative lupus nephritis were followed up for an average duration of 36.5 ± 26.11months. During follow-up, 6 (6/45, 13.33%) patients reached ESRD. A univariate analysis revealed that gender, leukocyturia, AI and CI were risk factors for renal outcome (HR: 0.182, 95% CI: 0.033–0.993, P = 0.049; HR: 1.463, 95% CI: 1.085–1.973, P = 0.013; HR: 1.402, 95% CI: 1.022–1.923, P = 0.036; HR: 1.440, 95% CI: 1.036-2.000, P = 0.030, respectively) and a subsequent multivariate analysis showed that leukocyturia was identified as an independent risk factor for renal outcome (HR: 1.456, 95% CI: 1.083–1.957, P = 0.013). However, we found that the leukocyturia was not an independent risk factor for renal outcome in endocapillary proliferative IgA nephropathy using the Cox hazard model for multivariate survival analysis (HR: 1.069, 95% CI: 0.494–2.312, P = 0.866) (Table 5).