This is a test to diagnose systemic lupus erythematosis (SLE). Nuclear material from lysed WBC is incubated with the patient's serum and neutrophils. If antibodies against nuclear material is present, neutrophils would phagocytize the antibody bound complex. A positive result is one in which neutrophils with a homogenous red-purple inclusion that distends the cell's cytoplasm is found. Of patients with active SLE, 70 to 80% will have positive LE prep.