Proteinuria selectivity index as a prognostic biomarker in lupus nephritis

Proteinuria selectivity index in renal disease

One of the main barriers to early detection and subsequent prevention of kidney diseases is the accessibility and feasibility of testing, especially in urine research. The proteinuria selectivity index (PSI or SI) is a method used to assess changes in glomerular permeability in glomerular diseases. It describes the pattern of proteinuria by comparing the clearance rates of large molecular proteins and transferrin, categorizing it as selective or non-selective. PSI is widely applied for kidney disease classification, prediction of corticosteroid efficacy, and prognosis. Herein, we reviewed the clinical applications and recent advancements of PSI in glomerular diseases, compared it with commonly used renal function biomarkers, and discussed the future research directions for PSI as a potential predictive marker for response to specific biologics.

Albumin-to-protein ratio in spot urine samples for analysis of proteinuria selectivity in chronic kidney disease

INTRODUCTION

The albumin-to-creatinine ratio and total protein-to-creatinine ratio in spot urine samples have already been validated as surrogates for 24-hour albuminuria and proteinuria measurements. Thus, we hypothesized that the type of proteinuria, detected by the electrophoretic pattern of 24-hour urine, could be predicted by the simple proportion of albumin in the total urine protein content, using the albumin-to-protein ratio (APR). Our study sought to validate the use of APR as a cheaper substitute for urinary protein electrophoresis (UPE).

METHODS

Using different mathematical models, we compared, the albumin fraction in 24-hour urine samples by electrophoresis and the APR ratio in spot samples from 42 outpatients with chronic kidney disease (CKD).

RESULTS

A strong log-order correlation r = 0.84 (0.75-0.92; 95% CI, p = 0.001) was observed between APR and the albumin fraction in the UPE.

CONCLUSION

The APR can substitute electrophoresis in CKD outpatients.

Razão albumina/proteína em amostras isoladas de urina para análise da seletividade de proteinúria na doença renal crônica

Resumo Introdução: A utilização da razão albumina/creatinina e da razão proteína total/creatinina em amostras isoladas de urina já foram validadas como substitutos para a albuminúria e proteinúria em 24 horas. Assim, nossa hipótese é que o tipo de proteinúria, dado pelo padrão eletroforético da urina de 24 horas, poderia ser previsto pela simples proporção de albumina no conteúdo total de proteínas na urina, utilizando a razão albumina/proteína (RAP). O presente estudo procurou validar o uso da RAP como um substituto mais prático e de menor custo da eletroforese de proteínas urinárias (EPU). Métodos: Foram utilizados diferentes modelos matemáticos a fim de comparar a fração de albumina pela eletroforese em amostras de urina de 24 horas e a RAP em amostras isoladas em 42 pacientes ambulatoriais com doença renal crônica. Resultados: Foi observada uma forte correlação logarítmica r = 0,84 (0,75–0,92; 95% CI, p = 0,001) entre a RAP e a fração de albumina pela EPU. Conclusão: A RAP pode substituir a eletroforese urinária em pacientes renais crônicos ambulatoriais.

Comparative efficacy and safety of mycophenolate mofetil and cyclophosphamide in the induction treatment of lupus nephritis: A systematic review and meta-analysis

BACKGROUND

Lupus nephritis (LN) remains a predominant cause of morbidity and mortality in SLE. Here we performed a meta-analysis to evaluate the efficacy and safety of the induction treatment with mycophenolate mofetil (MMF) and cyclophosphamide (CYC) for LN.

METHODS

Relevant literature was searched by computer from the establishment of the database to November 2019. A meta-analysis was conducted to analysis the efficacy and safety between mycophenolate mofetil and cyclophosphamide as induction therapy in LN patients. The primary end-point was response to urine protein, serum creatinine (Scr) and serum complement C3, and the secondary end-points were complete remission and adverse reactions.

RESULTS

Eighteen articles were selected for the final meta-analysis, involving 1989 patients with LN, of which the renal biopsy result could be classified into class III-V according to the standards of WHO/ISN. The results revealed that MMF was superior to CYC in increasing the level of serum complement C3 [SMD = 0.475, 95%CI (0.230-0.719)] and complete remission [RR = 1.231, 95%CI (1.055-1.437)]. Furthermore, the subgroup analysis showed that it was in Asian patients, rather than in Caucasian patients, that CYC exerted a better effect on lowering the level of urine protein (UPRO) than MMF [SMD = 0.405, 95%CI (0.081-0.730)]. Besides, when the initial UPRO level was less than 4 g/day, the effect of CYC was better than MMF [SMD = 0.303, 95%CI (0.014-0.591)]. There was no significant difference between MMF and CYC in improving Scr [SMD = 0.090, 95%CI (-0.060-0.239)]. When it came to the comparison of safety between MMF and CYC, the meta-analysis showed that MMF was superior to CYC in decreasing infection in Caucasian patients [RR = 0.727, 95%CI (0.532-0.993)], reducing the risk of leukopenia and menstrual abnormalities in Asian patients and lowering the frequency of gastrointestinal symptoms [RR = 0.639, 95%CI (0.564-0.724)], independent of race.

CONCLUSIONS

MMF precedes CYC in improving serum complement C3 and complete remission regardless of race, as well as shows fewer adverse drug reactions in the induction treatment of LN belonging to type III-V. But for Asian patients or those initial UPRO levels are less than 4 g/day, CYC may be superior to MMF.

Immunoglobulin G/albumin staining in tubular protein reabsorption droplets in minimal change disease and focal segmental glomerulosclerosis

BACKGROUND

Some renal biopsies cannot distinguish minimal change disease (MCD) from primary focal segmental glomerulosclerosis (FSGS) because of inadequate sampling and/or a lack of sampled glomeruli with segmental sclerosis. As protein excretion in MCD has been described as being albumin-selective, we examined whether the ratio of immunoglobulin G (IgG)/albumin staining in protein reabsorption droplets (tPRD) might help distinguish MCD from FSGS.

METHODS

Frozen tissue from 144 native renal biopsies from patients with nephrotic syndrome and a diagnosis of MCD or FSGS [73 MCD, 30 FSGS tip variant (FSGS-tip), 38 FSGS-not otherwise specified (FSGS-NOS), 3 FSGS collapsing] was retrospectively stained by direct immunofluorescence for IgG and albumin; none of these samples showed diagnostic lesions of FSGS. IgG and albumin staining of tPRD were graded on a scale of 0 to 3+ based on the distribution and intensity of staining.

RESULTS

Mean (standard deviation) IgG/albumin staining ratios were 0.186 ± 0.239 for MCD, 0.423 ± 0.334 for FSGS-tip (P = 0.0001 versus MCD) and 0.693 ± 0.297 for FSGS-NOS (P < 0.0001 versus MCD; P = 0.0001 versus FSGS-tip). Of 84 biopsies with a ratio ≤0.33, 63 (75%) showed MCD, whereas among 21 with a ratio of 1.0, all but one showed FSGS (15 FSGS-NOS).

CONCLUSIONS

In summary, IgG/albumin staining in tPRD was correlated with histologic diagnosis in renal biopsies with MCD and FSGS. A ratio of ≤0.33 was associated with MCD, whereas a ratio of 1.0 was most often seen with FSGS-NOS.

New selectivity index calculated using protein fraction as a substitute for the conventional selectivity index

BACKGROUND

Selectivity index (SI) of proteinuria, calculated using the clearance ratio of immunoglobulin G to transferrin, predicts the response to glucocorticoids in patients with nephrotic syndrome. However, there is disagreement regarding the suitability of SI. Therefore, alternate indices should be considered. This study investigated whether or not selectivity index protein fraction (SIPF) was inferior to SI for the prediction of the response to glucocorticoids.

METHODS

Forty-nine patients with nephrotic syndrome were evaluated. On the basis of molecular weight and protein fraction, as an inexpensive substitute for SI, the clearance ratio of the albumin to γ fractions measured in serum and urine protein fractions was defined as SIPF. The quality of SIPF was examined. Moreover, the best cutoff value of SIPF was determined; and SIPF distribution, according to histopathological diagnosis by renal biopsy, was examined.

RESULTS

SIPF was strongly correlated with SI (r = 0.79, P < 0.001). The area under the receiver operating characteristic (ROC) curve of SIPF and SI was not significantly different (P = 0.18). The best cutoff value of SIPF was 0.45. In the group with SIPF > 0.45, only two patients with minimal change disease (MCD) achieved complete remission. In the group with SIPF ≤ 0.45, all patients with MCD achieved complete remission, although eight patients with other histopathological diagnoses did not achieve complete remission.

CONCLUSIONS

Analysis of protein fractions as a substitute for SI may be useful for predicting response to glucocorticoids in patients with nephrotic syndrome.

Combined utilization of untimed single urine of MCP-1 and TWEAK as a potential indicator for proteinuria in lupus nephritis: A case-control study

The aim of this study was to determine whether combined utilization of untimed single urine monocyte chemoattractant protein 1 (uMCP-1) and tumor necrosis factor (TNF)-like weak inducer of apoptosis (uTWEAK) could serve as a screening test for proteinuria in patients with lupus nephritis (LN).A case-control study that contained 39 biopsy-proven LN patients, 20 non-LN systemic lupus erythematosus (SLE) patients, and 10 healthy controls (HCs) were carried out. Correlations between uMCP-1, uTWEAK, and traditional clinical markers were analyzed by Spearman correlation test. Diagnostic values of uMCP-1, uTWEAK, and urine albumin/creatinine ratio (uACR) in the assessment of proteinuria were investigated by receiver operating characteristic (ROC) curves.Biopsy-proven LN patients showed higher levels of uMCP-1 and uTWEAK than non-LN patients. uMCP-1 and uTWEAK were elevated in renal active patients (rSLEDAI ≥4). Both uMCP-1 and uTWEAK showed significant correlation with patients' rSLEDAI, 24-hour urine proteinuria (24hr UP), and anti-double-stranded DNA (anti-dsDNA) antibodies. No correlations of these 2 biomarkers between cystatin C (Cys-C), creatinine (Cr), and blood urea nitrogen (BUN) were observed. An algorithm combining the moderate sensitivity of uMCP-1 and high specificity of uTWEAK displayed great specificity and sensitivity for proteinuria screening.Both uMCP-1 and uTWEAK were positively correlated with the impairments of LN, and the combined utility of untimed single uMCP-1 and uTWEAK might be used as potential predictors for proteinuria in LN.