The proper use and interpretation of serologic testing for diagnosing autoimmune diseases presents a challenge to clinicians for several reasons. Most laboratory tests for autoimmune disease are significantly less than 100% sensitive or specific. In addition, different techniques for the same antibody test may give different results, such as indirect immunofluorescence and multiplex bead assay for antinuclear antibody. Autoantibody testing should only be performed in the context of the clinical workup of patients who have a reasonable likelihood of having the disease for which the testing is relevant. Otherwise, the predictive value of a positive test is too low. Particularly with antinuclear antibody and antineutrophil cytoplasmic antibody testing, clinicians must know the methodology through which the tests are being performed, and should develop a relationship with the laboratory pathologist so that inconsistent or surprising results can be investigated.