Study Suggests Reduced Use of Direct Immunofluorescence Biopsies

Research from Boston suggested a knowledge gap among dermatologists related to the opportunity for high-value, cost-conscious use of direct immunofluorescence (DIF) biopsies, despite daily use in the medical community.

Immunofluorescence (IF) had been integral in the identification of antigen-bound antibodies in both tissue and bodily fluids as early as the 1940s, when it was first used to detect tissue microorganisms.

The DIF, which is 1 of 2 IF assays, uses Fluorochrome-labeled antibodies to detect the presence of immunoreactant deposition in a patient’s skin. Historically, a panel of antibodies to immunoglobulin (Ig) G, IgA, IgM, complement C3, fibrin, and albumin have been used.

The process has been integral in the workup of patients with suspected vasculitis, as well for evaluation of IgA vasculitis in cases of suspected IgA vasculitis with systemic involvement, and in the diagnosis of lichen planus, porphyria, and connective tissue disease (CTD).

In the study, investigators led by Thomas Horn, MD, MBA, Department of Dermatology, Massachusetts General Hospital, sought to gain a better understanding of the clinical utility and diagnostic value of performing DIF using the full antibody panel.

As such, they compared the frequency of positivity for each immunoreactant associated with submitted diagnosis in DIF biopsies submitted to the Massachusetts General Physician Organization (MGPO) Dermatopathology Associates Laboratory over 8 years.

The Methods

The 8-year quality improvement study incorporated samples of a total of 2050 biopsies submitted between April 1, 2012, and June 12, 2020, at MGPO Dermatopathology Associates in Newton, Massachusetts.

All specimens were received in Michel’s Transport Me- dium and processed for DIF according to standard protocol, using fluorescein isothiocyanate–conjugated anti-IgG, anti- IgA, anti-IgM, anti-C3, anti-fibrinogen, and anti-albumin

Data from each specimen would be compiled into a spreadsheet that compared clinical impression with the final pathologic diagnosis as well as the pattern and specific positive antibodies.

Clinical impression categories included: pemphigoid group (bullous pemphigoid, cicatricial pemphigoid, etc.), dermatitis herpetiformis, pemphigus group (pemphigus vulgaris, pemphigus foliaceus, IgA pemphigus, paraneoplastic pemphigus, and pemphigus vegetans), linear IgA disease, immunobullous not otherwise specified (NOS), CTD, lichen planus, porphyria, and vasculitis.

The Results

Of the total of 2050 samples in the study, 367 (17.9%) were positive.

Biopsy results were categorized by the following clinical impressions: pemphigoid (714 [34.8%]), immunobullous/blistering disorder NOS (552 [26.9%]), dermatitis herpetiformis (239 [11.7%]), vasculitis (210 [10.2%]), CTD (209 [10.2%]), pemphigus (73 [3.6%]), lichen planus (24 [1.2%]), linear IgA disease (15 [0.7%]), or porphyria (14 [0.7%])

Horn and colleagues also noted the pattern of immunoreactant deposition in DIF-positive pemphigoied biopsies, of which there were 200 cases.

Of these, 120 (60.0%) cases positive for pemphigoid had a concurrent H&E biopsy, which showed H&E evidence of pemphigoid, with the exception of 3 cases: 1 for interface dermatitis, a nonspecific erosion, and 1 case in which the H&E biopsy was of perilesional skin.

Additionally, 5 cases were diagnosed as linear IgA disease on DIF , all of which showed linear deposition of IgA at the basement membrane zone with the exception of 1 case that showed weak linear deposition of IgM at the basement membrane zone in addition to linear IgA.

Only IgG, IgA, and C3 were 100% sensitive (95% CI, 98.6%- 100.0%) and 100% specific (95% CI, 99.7%-100.0%) in detecting primary immunobullous disorders, and only IgA, C3, and fibrin were 100% sensitive (95% CI, 94.8%-100.0%) and 100% specific (95% CI, 97.5%-100.0%) in detecting vasculitis.

Overall, investigators found the use of DIF biopsies to be largely unnecessary and suggested that limiting the use of DIF could reduce costs without compromising patient care.

“A DIF protocol tailored to the submitting diagnosis may enhance cost-effectiveness without loss of test sensitivity and specificity,” the team wrote.