title: Lupus band test
text: # Lupus band test
  
  Lupus band test is done upon skin biopsy, with direct immunofluorescence staining, in which, if positive, IgG and complement depositions are found at the dermoepidermal $junction.^{:212}$ This test can be helpful in distinguishing systemic lupus erythematosus (SLE) from cutaneous lupus, because in SLE the lupus band test will be positive in both involved and uninvolved skin, whereas with cutaneous lupus only the involved skin will be $positive.^{:212}$
  
  The minimum criteria for positivity are:
  
  * In sun-exposed skin: presence of a band of deposits of IgM along the epidermal basement membrane in 50% of the biopsy, intermediate (2+) intensity or more.
  * In sun-protected skin : presence of interrupted (i.e. less than 50%) deposits of IgM along the epidermal basement membrane, intermediate (2+) intensity or more.
  
  The presence of other immunoglobulins (especially IgA) and/or complement proteins (especially C4) increases the specificity of a positive test.
  
  