Utility of anti-immunoglobulin IgA, IgG, IgM, Kappa, Lambda - FITC (conjugate) cocktail in routine renal pathology practice

Abstract Background Immunofluorescence studies on frozen sections are an essential component in the evaluation of renal biopsies. The basic panel in most centres constitutes IgG, IgA, IgM, C3c, C1q, Kappa and Lambda light chain antibody testing. The purpose of this panel is to detect immunoglobulin or complement deposits and further subclassify the disease based on the location, intensity and pattern of immunoglobulin and complement staining. However, there are a substantial proportion of nephropathies that do not show any obvious immune-deposits on immunofluorescence. We currently, do not have any evidence-based alternative immunofluorescence panel to rule out these conditions. This study aims to evaluate the utility of anti-immunoglobulin IgA, IgG, IgM, Kappa, Lambda - FITC cocktail immunofluorescence on renal biopsy frozen sections with emphasis on its role as a primary screening panel in conjunction with C3c and C1q. Methods Anti-immunoglobulin IgA, IgG, IgM, Kappa, Lambda light chain - FITC cocktail immunofluorescence was performed on 593 consecutive native renal biopsies along with the routine panel comprising of the individual FITC labelled IgG, IgA, IgM, C3c, C1q, Kappa and Lambda light chain immunofluorescence stains. Results In 235 (39.6%) cases immune deposits (immune-complex mediated and monoclonal gammopathy-related) were present and the rest 354 (59.7%) cases were negative for immunoglobulin or complement deposits. Overall, the sensitivity, specificity, positive predictive value and negative predictive values of anti-immunoglobulin IgA, IgG, IgM, Kappa and Lambda - FITC cocktail in distinguishing immune-complex/immunoglobulin-mediated glomerulopathies from non-immune complex/immunoglobulin-mediated glomerulopathies were 100% each. Conclusion Anti-immunoglobulin IgA, IgG, IgM, Kappa and Lambda - FITC cocktail when used in conjunction with C3c and C1q, can be an effective first line investigation in all native renal biopsies. Further, testing with the individual FITC labelled IgG, IgA, IgM, Kappa and Lambda light chain immunofluorescence can be performed, depending on the initial screening as described above. Overall, this algorithmic approach can save valuable resources.