Increased sensitivity and high specificity of indirect immunofluorescence in detecting IgG subclasses for diagnosis of bullous pemphigoid.

BACKGROUND: Indirect immunofluorescence (IIF) microscopy on monkey oesophagus is an important assay for the diagnosis of bullous pemphigoid (BP). Its relatively low sensitivity (60-80%) may be partly due to insufficient detection of minor IgG subclasses.

AIM: To determine the operating characteristics of an IgG subclass in IIF.

METHODS: We designed a retrospective, dual-centre, controlled cohort study on sera from 64 BP sera that had been rated as false negatives by traditional IIF microscopy, and assessed circulating IgG1 , IgG3 and IgG4 autoantibodies.

RESULTS: The sensitivities of IIF in detecting IgG1 , IgG3 , IgG4 and all three in combination were 45.3%, 18.8%, 32.8% and 48.4%, respectively. Specificities were > 97%.

CONCLUSION: Detection of IgG subclass (especially IgG1 and IgG4 ) autoantibodies by IIF on monkey oesophagus can significantly improve diagnostic performance of IIF microscopy for diagnosis of BP.