The composition of the lupus band test (LBT) on the sun-protected non-lesional (SPNL) skin in patients with cutaneous lupus erythematosus (CLE)

The objective of this study was to analyse the different immunoreactants at the dermo-epidermal junction (DEJ) of patients with cutaneous lupus erythematosus (CLE). Sun-protected non lesional (SPNL) skin biopsies from 65 patients with specific cutaneous manifestations of LE and from 18 patients with other dermatologic diseases were tested using the direct immunofluorescence (DIF) technique. Nineteen out of 65 patients with CLE were affected by systemic LE (SLE). We used the conventional chi-squared test to analyse statistical differences between CLE-SLE and CLE-non-SLE groups in the immunological composition of lupus band test (LBT). C3 was the most common component while IgM were the most frequent immunoglobulins (Igs) of LBT in LE patients. No immunoreactants could be demonstrated at the DEJ in patients with other dermatologic diseases. No statistical differences could be found between CLE-SLE and CLE-non-SLE groups as regards the detection of the different immunoreactants at the DEJ. A positive LBT (even for the presence of only one immunoreactant at the DEJ) performed on SPNL skin represents a useful and specific criterion to distinguish patients with lupus erythematosus (LE) from those without LE. We also believe in a prognostic value of a positive LBT on SPNL skin when the deposition of at least two immunoreactants is demonstrated, and especially if the deposits are composed of IgG.