Comparative evaluation of immunoperoxidase versus immunofluorescent techniques in interpretation of kidney biopsies

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.

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.

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.

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.