Direct immunofluorescence on formalin-fixed, paraffin-embedded versus fresh frozen human renal biopsies: a comparative study

ABSTRACT

Background

The data referring to the value of direct immunofluorescence on formalin-fixed, paraffin-embedded tissue (IF-Paraffin) in the diagnosis of renal diseases is controversial. The aim of this study was to investigate whether renal biopsies evaluated by routine immunofluorescence on frozen tissue (IF-Frozen) would yield adequate findings to confirm diagnoses when the IF-Paraffin technique was applied.

Methods

To show immunoglobulins, complement components, and light chains, 55 native renal biopsies were subjected to IF-Paraffin and IF-Frozen staining techniques. The intensity of the staining was compared, and the sensitivity and specificity were calculated.

Results

The IF-Paraffin technique showed a sensitivity of 89%, 81%, 86%, 30%, 71%, 60%, and 77% for IgG, IgM, IgA, C1q, C3, κ, and λ, respectively, whereas specificity was 91%, 100%, 100%, 96%, 94%, 98%, and 100%. It showed diagnostic findings in 87% of cases. Compared to cases that had both IF-Paraffin and IF-Frozen staining techniques, 43 of 55 showed either equal intensity for the diagnostic immunoglobulin/complement or a little difference.

Conclusions

Direct immunofluorescence on formalin-fixed, paraffin-embedded sections cannot replace immunofluorescence on frozen sections in the assessment of renal biopsies, but may be a “salvage technique” when frozen tissue is insufficient or unavailable and must be interpreted with great caution.

KEYWORDS:

• Immunofluorescence
• complements
• paraffin
• proteinase K
• renal biopsy

Acknowledgments

The author thanks two renal histopathologists, Professor Dr. Liwaa H. Mahdi and Dr. Sabah N. Mohammed, for their assistance in the evaluation and scoring of the immunofluorescence intensity, and the medical staff in the histopathology and nephrology departments at Al-Sader Medical City for their kind assistance and support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are openly available in “zenodo” at https://doi.org/10.5281/zenodo.10321375.

Ethical approval

The current study was approved by the Nursing Faculty‘s Ethical Review Board at the University of Kufa in Iraq (#:A405/18 on June 8, 2021).

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.