- Design
- Single-centre retrospective diagnostic accuracy study
- Population
- 100 consecutive sera from suspected bullous pemphigoid with epidermal-pattern IgG on salt-split skin
- Primary outcome
- ELISA sensitivity by antigen target
- Effect
- LABD97 87% vs BP180 NC16A 66% vs BP230 52%; 83% of double-negative cases LABD97 positive
Standard antigen-specific serology for bullous pemphigoid misses about a quarter of patients who have epidermal-side IgG on indirect immunofluorescence. A University of Utah laboratory tested 100 consecutive sera from suspected pemphigoid with that immunofluorescence pattern against three ELISA targets.
An IgG ELISA using LABD97, a larger shed fragment of BP180, was positive in 87%. The commercial BP180 NC16A ELISA was positive in 66% and the BP230 ELISA in 52%. Of the patients negative on both commercial assays, 83% were LABD97 positive.
The point is diagnostic: a negative NC16A ELISA does not rule pemphigoid out, particularly in older patients with itch and few blisters. The study is single-centre, retrospective and without clinical follow-up, and the LABD97 assay is not widely available.
In practice, keep biopsy with direct immunofluorescence at the centre of diagnosis, and do not discount pemphigoid because standard ELISA is negative.
- A negative BP180 NC16A ELISA does not exclude bullous pemphigoid
- Take a perilesional biopsy for direct immunofluorescence when pemphigoid is suspected
- Consider indirect immunofluorescence on salt-split skin when ELISA is negative
- Suspect non-bullous pemphigoid in older adults with chronic itch and eczematous or urticarial plaques
Why it matters
It shows how many genuine pemphigoid cases standard serology leaves undiagnosed.
Don't overread it
Specificity was not assessed, so a positive LABD97 result alone cannot confirm the diagnosis.
The statistics, in plain English
Sensitivity is the share of true cases a test catches: 87 of 100 for LABD97 against 66 for NC16A. Specificity, how often it is negative in people without pemphigoid, was not reported here, so the false-positive rate is unknown.
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