From the Guidelines
For accurate direct immunofluorescence (DIF) in suspected Henoch-Schönlein purpura (HSP), the optimal approach involves taking a biopsy from a fresh, erythematous lesion and using Michel's transport medium for preservation, as saline is not ideal for long-term preservation and must be processed within 24-48 hours 1. When considering the steps for accurate DIF, the following points are crucial:
- The biopsy site should be a fresh, erythematous lesion less than 24 hours old, typically from the lower extremities.
- While saline can be used initially for transport, it's essential to transfer the specimen to Michel's transport medium within 24 hours to prevent degradation of immunoreactants, as noted in the guidelines for managing bullous pemphigoid 1.
- Alternatively, the tissue can be snap-frozen in liquid nitrogen.
- The biopsy should include adequate dermis since HSP shows IgA deposition in the small vessels of the papillary and reticular dermis.
- Processing should occur promptly, with the specimen sectioned at 4-6 μm thickness and stained with fluorescein-conjugated antibodies against IgA, IgG, IgM, C3, and fibrinogen.
- Proper handling temperature (4°C) during transport is crucial.
- The pathologist should be informed about the clinical suspicion of HSP to ensure appropriate processing.
- The characteristic finding in HSP is granular IgA deposition in vessel walls, which helps distinguish it from other forms of vasculitis. It's also important to note that the use of Michel's medium allows for a longer delay in processing, up to 2 weeks, compared to saline, which requires processing within 24-48 hours 1.
From the Research
Steps for Accurate Direct Immunofluorescence (DIF) in Vasculitis with High Suspected Henoch-Schönlein Purpura
- The first step is to perform a skin biopsy, which is a crucial diagnostic tool for Henoch-Schönlein purpura (HSP) 2, 3.
- The biopsy should be taken from uninvolved, normal-appearing skin, as this may provide better tissue morphology and more accurate DIF results 2.
- The biopsy specimen should be transferred in a suitable medium, such as saline, to preserve the tissue and prevent degradation of immunoglobulins 2.
- Direct immunofluorescence (DIF) study should be performed on the biopsy specimen to detect deposits of immunoglobulins, such as IgA, IgG, and IgM, and complement components, such as C3 2, 4, 5, 6.
- The DIF findings should be interpreted in conjunction with clinical and histopathological features to confirm the diagnosis of HSP 4, 3, 5, 6.
Site of Biopsy and Media of Transfer
- The site of biopsy is typically uninvolved, normal-appearing skin, which may provide better tissue morphology and more accurate DIF results 2.
- The media of transfer is usually saline, which is used to preserve the tissue and prevent degradation of immunoglobulins 2.
Other Steps for Accurate DIF Results
- The biopsy specimen should be handled and processed carefully to prevent degradation of immunoglobulins and other proteins 4, 5, 6.
- The DIF study should be performed using a panel of antibodies against different immunoglobulins and complement components to detect specific deposits 4, 5, 6.
- The DIF findings should be interpreted by an experienced pathologist or immunologist to ensure accurate diagnosis and classification of the disease 4, 5, 6.
- The DIF results should be correlated with clinical and histopathological features to confirm the diagnosis and guide treatment decisions 4, 3, 5, 6.