Mucosal DIF biopsy shows high sensitivity for diagnosing MMP
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Direct immunofluorescence microscopy bested serologic analysis as a diagnostic method for mucous membrane pemphigoid, according to a study.

An accurate diagnosis of mucous membrane pemphigoid (MMP) is essential to reduce diagnostic and therapeutic delay.

This study aimed to assess the diagnostic accuracy of direct immunofluorescence microscopy on mucosal biopsy specimens and immunoserology in a large cohort of patients with suspected MMP.

This retrospective cohort study was carried out in a single tertiary care center for blistering diseases. Eligible participants were patients with suspected MMP and paired data on at least a mucosal biopsy specimen for direct immunofluorescence microscopy (DIF) and indirect immunofluorescence microscopy (IIF) on a human salt-split skin substrate (SSS). In addition, an optional DIF test on a skin biopsy specimen and one or more performed routine immunoserologic tests were analyzed.

-- Of the 787 participants, 121 received the diagnosis of MMP (50 men, 71 women; mean age at diagnosis, 60.1 years).

-- Sixty-seven of the patients with MMP (55.4%) had monosite involvement, of which oral site was the most frequently affected (51 [42.1%]).

-- No significant difference was found between the sensitivity of DIF on a perilesional buccal biopsy and a normal buccal biopsy (89.3% vs 76.7%).

-- Three patients with solitary ocular involvement showed a positive DIF of only the oral mucosa.

-- In 6 patients with a negative mucosal DIF, a skin biopsy confirmed diagnosis of MMP.

-- Overall, IIF SSS was less sensitive (44.6%), but highly specific (98.9%).

-- The sensitivity of immunoblot (66.1%) was higher compared to SSS, but with lower specificity (91.3%).

Conclusively, this comparative diagnostic accuracy study of a cohort of 787 patients found a high sensitivity of a mucosal DIF biopsy for diagnosis of MMP, and lower sensitivity of serologic analysis. A biopsy can be taken from either perilesional or normal buccal mucosa. An additional DIF biopsy of another mucosal site or of affected or unaffected skin may increase the diagnostic yield and is recommended in patients with negative DIF results and high clinical suspicion.