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Background & objectives: Activation of renin-angiotensin system and tubulointerstitial damage might be seen in pre-albuminuria stage of diabetic nephropathy (DN). Here, diagnostic utility of four urinary biomarkers [Angiotensinogen (Angio), Interleukin (IL)-18, Neutrophil Gelatinase-Associated Lipocalin (NGAL) and Cystatin] during pre-albuminuria stages of non-hypertensive type 2 diabetes patients was studied. Methods: A total of 952 type 2 diabetes mellitus (T2DM) patients were screened for nephropathy [estimated glomerular filtration rate (eGFR) ?120 ml/min and albumin–creatinine ratio (ACR) ?30], and 120 patients were followed up for one year. At one year, they were classified into hyperfiltration (43), normoalbuminuria (29) and microalbuminuria (48) groups. Another 63 T2DM patients without nephropathy were included as controls. Hypertension, patients on angiotensin-converting enzyme inhibitor/angiotensin receptor blocker, eGFR <60 ml/min/1.73 m2 and all proteinuric conditions were excluded. All were subjected to testing for urine protein, ACR, HbA1C, eGFR, along with urinary biomarkers (IL-18, cystatin-C, NGAL and AGT). Comparative analysis of all the diagnostic tests among different subgroups, correlation and logistic regression was done. Results: Urinary IL-18/Cr, cystatin/creatinine (Cr) and AGT/Cr levels were higher in groups of hyperfiltration (13.47, 12.11 and 8.43 mg/g), normoalbuminuria (9.24, 11.74 and 9.15 mg/g) and microalbuminuria (11.59, 14.48 and 10.24 mg/g) than controls (7.38, 8.39 and 1.26 mg/g), but NGAL/Cr was comparable. The area under receiver operating characteristic curve (AUC) and sensitivity of AGT to detect early CKD were higher than ACR and eGFR (0.91 and 90.4%, 0.6 and 40% and 0.6 and 37%, respectively). AUC values of other biomarkers, namely IL-18/Cr, cystatin/Cr and NGAL/Cr, were 0.65, 0.64 and 0.51, respectively. Angio/Cr and IL-18/ Cr showed correlation with log albuminuria (r=0.3, P=0.00, and r=0.28, P=0.00, respectively). NGAL showed correlation with log eGFR (r=0.28 P=0.00). Multivariate logistic analysis showed that odds ratio of developing nephropathy was 7.5 times with higher values of log Angio/Cr. Interpretation & conclusions: Urinary AGT showed a higher diagnostic value than ACR and eGFR followed by IL-18 and cystatin to diagnose DN during pre-albuminuric stages.
RESUMO
Background: Immunofluorescence (IF) on frozen sections has been considered to be the gold standard for evaluation of kidney biopsy specimens. Immunohistochemistry (IHC) method can also be used for this purpose with advantages of being applicable on paraffin embedded tissue, providing permanent sections, and not requiring a specialized microscope for interpretation. Our aim was to evaluate IHC as an alternative to IF in the diagnostic assessment of kidney biopsy specimens. Methods: One hundred kidney biopsy specimens were subjected to both IF and IHC staining for immunoglobulins (Ig), IgG, IgA, IgM and complement components c3 and c1q. IF staining was done on frozen sections. IHC staining was performed on paraffin‑embedded tissue following proteolytic antigen retrieval. The sections were evaluated, and the results of IHC were compared with IF. Results: Concordant observations were 98%, 87%, 89%, 83%, and 89% for IgA, IgM, IgG, C3 and C1q, respectively. The sensitivity of IHC method for Igs was found to be high (92%, 86.5%, and 95.1%, respectively for IgA, IgM, and IgG). 91% cases showed concordance of the intensity of the deposits while 100% cases showed a concordance of the pattern. Statistically, there was no significant difference in outcomes between IF and IHC for IgA, IgM, and IgG. However, statistically significant difference was found in the results for complement proteins. Conclusion: In this study, it is documented that IHC is, with few exceptions, equal to IF for the detection of Igs. Standardized immunoperoxidase method on the paraffin embedded, formalin fixed needle kidney biopsies could successfully replace the IF method in the diagnosis of glomerulonephritis.