False-Negative Rate of Direct Immunofluorescence on Lower Extremities in Bullous Pemphigoid

Area of Science:

• Dermatology
• Immunology
• Pathology

Background:

• Bullous pemphigoid (BP) is the most common autoimmune blistering skin disease.
• Direct immunofluorescence (DIF) on perilesional skin is the gold standard for BP diagnosis.
• A clinical opinion suggests lower extremities have a high false-negative rate (FNR) for DIF in BP diagnosis, based on older studies.

Purpose of the Study:

• To re-evaluate the FNR of DIF by anatomical site in bullous pemphigoid diagnosis.
• To investigate if lower extremities indeed have a high FNR for DIF in BP diagnosis.

Main Methods:

• Retrospective study of bullous pemphigoid cases from 2012 to 2018.
• Evaluation of DIF FNR based on biopsy anatomical site (lower extremity, trunk, upper extremity).
• Inclusion of 79 patients diagnosed with BP using clinical, histological, and DIF data.

Main Results:

• A total of 4 false-negative DIF biopsies were identified among 79 patients.
• The FNR for lower extremity DIF was 10% (2 cases), compared to 4% for the trunk and 3% for the upper extremity.
• No statistically significant difference in FNR was found between anatomical sites.

Conclusions:

• The study did not demonstrate a high false-negative rate for direct immunofluorescence on lower extremities in bullous pemphigoid diagnosis.
• The findings challenge the prevailing clinical opinion regarding lower extremity biopsy sites for BP diagnosis.
• Further research may be warranted to confirm these findings across different populations and institutions.