title: Immunofluorescence on paraffin embedded renal biopsies: Experience of a tertiary care center with review of literature.
abstract: OBJECTIVE
  To describe the technique of immunofluorescence on paraffin embedded tissue sections and discuss the potential pitfalls with an in depth review of literature.
  
  
  METHODS
  Immunofluorescence is integral to diagnostic renal pathology. Immunofluorescence on paraffin embedded renal biopsies (IF-P) after enzyme treatment has been described in literature, however has not found widespread use in renal pathology laboratories. In our laboratory proteinase K digestion of paraffin embedded renal biopsy material was standardized and applied prospectively in cases where immunofluorescence on fresh frozen tissue was non contributory or not possible. Diagnostic utility was assessed and in a cohort of cases comparison of intensity of staining with routine immunofluorescence was performed.
  
  
  RESULTS
  Over the 5-year study period, of the 3141 renal biopsies received IF-P was performed on 246 cases (7.7%) and was interpretable with optimal digestion in 214 cases (6.8%). It was of diagnostic utility in the majority of cases, which predominantly included glomerular disease. Non-diagnostic IF-P was found in membranous nephropathy (2 of 11 cases), membranoproliferative glomerulonephritis (2 of 32 cases), lupus nephritis (1 of 25 cases), post infectious glomerulonephritis (1 of 11 cases) and chronic glomerulonephritis (3 of 8 cases). Comparing cases with both routine IF and IF-P, 35 of 37 showed either equal intensity or a minor difference in intensity of staining (1+) for the diagnostic immunoglobulin/complement. Technically assessment of immunofluorescence on the paraffin embedded tissue was found to be easier with clearly observed morphology, however a false positive staining pattern was observed in under-digested tissue.
  
  
  CONCLUSIONS
  As a "salvage" technique, immunofluorescence on paraffin embedded renal biopsies is of great diagnostic utility, however not without pitfalls.
authors.affiliation: Geetika Singh, Lavleen Singh, Ranajoy Ghosh, Devajit Nath, Amit Kumar Dinda, Department of Pathology, All India Institute of Medical Sciences, New Delhi 110029, India.
authors.forename: Geetika
authors.initials: G
authors.lastname: Singh
authors.affiliation: Geetika Singh, Lavleen Singh, Ranajoy Ghosh, Devajit Nath, Amit Kumar Dinda, Department of Pathology, All India Institute of Medical Sciences, New Delhi 110029, India.
authors.forename: Lavleen
authors.initials: L
authors.lastname: Singh
authors.affiliation: Geetika Singh, Lavleen Singh, Ranajoy Ghosh, Devajit Nath, Amit Kumar Dinda, Department of Pathology, All India Institute of Medical Sciences, New Delhi 110029, India.
authors.forename: Ranajoy
authors.initials: R
authors.lastname: Ghosh
authors.affiliation: Geetika Singh, Lavleen Singh, Ranajoy Ghosh, Devajit Nath, Amit Kumar Dinda, Department of Pathology, All India Institute of Medical Sciences, New Delhi 110029, India.
authors.forename: Devajit
authors.initials: D
authors.lastname: Nath
authors.affiliation: Geetika Singh, Lavleen Singh, Ranajoy Ghosh, Devajit Nath, Amit Kumar Dinda, Department of Pathology, All India Institute of Medical Sciences, New Delhi 110029, India.
authors.forename: Amit Kumar
authors.initials: AK
authors.lastname: Dinda
keywords: Enzymatic digestion; Immunofluorescence on paraffin section; Proteinase K; Renal biopsy; Salvage technique