Lupus band test (LBT)
It is a diagnostic procedure that is used to detect deposits of immunoglobulins and complement components along the dermoepidermal junction in patients with lupus erythematosus (LE).
The LBT is positive in about 70%–80% of sun-exposed skin in pts with systemic LE (SLE), and in about 55% of SLE cases in non sun exposed skin. It is demonstrable as a linear band at the basement membrane zone on immunofluorescence tetsing. All major immunoglobulin classes (IgG, IgM, and IgA) and various complement components have been identified in these DEJ deposits. The test is done on the skin biopsy, usually with direct immunofluorescence staining. The most frequent immunoglobulin class deposited is IgM, which is seen in about 90% of lesional skin biopsies, whereas the least frequently seen class is IgA.
A positive LBT may serve as a prognostic indicator in patients with an established diagnosis of LE, as it correlates with severe extracutaneous disease, mainly lupus nephritis, and with anti-dsDNA antibodies. The usefulness of the LBT as a diagnostic procedure in LE patients is also well established. The positive result of this test within the uninvolved skin is a strong indicator of LE.
