Effectiveness of direct immunofluorescence for diagnosing autoimmune bullous diseases: data from the Central European referral department.

Introduction: Autoimmune bullous disorders (AIBD) are a heterogeneous group of diseases resulting from autoantibodies production. Nowadays, direct immunofluorescence (DIF) is the basic diagnostic tool for diagnosing AIBD. Aim: This study was performed to assess the percentages of positive and negative DIF tests performed in individuals clinically suspected to suffer from AIBD in a single Central European referral department laboratory and to propose ways to improve the effectiveness of DIF in AIBD imaging diagnostics. Material and methods: A total of 1985 consecutive tests were collected during 9 consecutive years (2016-2024). We analysed the total number of results, the percentages of positive and negative results year by year, and according to the unit that sent material for testing. Results: We found that almost one-third of the tests were positive (30.88% overall, over 9 years). The percentage of positive results has varied from year to year (from 26.22% in 2016 to 38.89% in 2023). The percentage of positive results was higher in outpatient clinics than in hospital wards (33.7% vs. 22.9%; Conclusions: DIF should be performed thoughtfully at both clinical and laboratory levels, and approximately 31% of positive results should be regarded as a good outcome. To increase this percentage, specialised units should be maintained to keep up with the constant development of knowledge and experience in AIBD. Negative DIF results could also be useful in differential diagnostics of AIBD, but their percentage should be minimized.