False–Negative Rate of Direct Immunofluorescence on Lower Extremities in Bullous Pemphigoid The American Journal of Dermatopathology

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• In this retrospective study, 79 patients with clinical and histopathologic findings of bullous pemphigoid and an associated direct immunofluorescence (DIF) specimen were reviewed to determine the false–negative rate of DIF by site. The most common anatomical sites for DIF were upper extremity (41.8%), trunk (29.1%), and lower extremity (25.3%). Of 4/79 false–negative specimens, 1 was taken from the upper extremity, 1 from the trunk, and 2 from the lower extremities. False–negative rates at each site were 3%, 4%, and 10%, respectively. There was no statistically significant difference in the false–negative rates between the lower leg and other sites (P = .246).

• Two previous studies and anecdotal experiences have led to the recommendation that the lower extremity should be avoided for DIF sampling. Based on this review of 79 patients, there was no difference in false–negative rates between anatomical sites. This study suggests that the lower extremity need not necessarily be avoided as a site for DIF in diagnosing bullous pemphigoid.

– Margaret Hammond, MD

Abstract 

Bullous pemphigoid (BP) is the most common autoimmune blistering disorder of the skin. It is typified by tense blisters with a subepidermal split and mixed dermal inflammatory infiltrate on histology. Biopsy of the perilesional skin for direct immunofluorescence (DIF) has become the gold standard in the diagnosis of BP. Currently there is a pervasive clinical opinion that the lower extremity is a site with a high false-negative rate (FNR) for DIF in the diagnosis of BP. This notion is primarily based on 2 early studies from the 1980s without more recent confirmatory studies. To readdress this question regarding the lower extremities, a retrospective study from 2012 to 2018 was performed in our institution that evaluated the FNR of DIF by an anatomical site in the diagnosis of BP. Cases of BP were identified using standard criteria (clinical and histological data reviewed in cases with negative DIF), and overall, 79 patients were included in the study. A total of 4 false-negative DIF biopsies were verified. Two negative DIF were from the lower extremity yielding a FNR of 10% compared with 4% on the trunk and 3% from the upper extremity, with no statistically significant difference by anatomical sites. Our study fails to demonstrate a high FNR of DIF from the lower extremity in the diagnosis of BP.

The American Journal of Dermatopathology

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

Am J Dermatopathol 2021 Jan 01;43(1)42-44, DM Perry, A Wilson, S Self, JC Maize 

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Benjamin Hidalgo-Matlock
Skin Care Physicians of Costa Rica

Clinica Victoria en San Pedro: 4000-1054
Momentum Escazu: 2101-9574

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