Clinical utility of testing for antineutrophil cytoplasmic antibodies.

Autoantibodies against various “self” intraor extracellular, cell surface-bound or soluble antigens are frequently present in the sera of patients with autoimmune diseases. Regardless of their precise role in the pathogenesis of these diseases, testing for autoantibodies constitutes an integral part of the initial diagnostic workup of patients with organ-specific or systemic autoimmune diseases. Diseases that affect specific organs— autoimmune thyroiditis (thyroid), myasthenia gravis (neuromuscular system), autoimmune cytopenias (hematopoietic system)—or multiple organs—systemic lupus erythematosus (SLE), scleroderma, Sjögren’s syndrome—are typical examples of diseases for which determination of different autoantibodies aids the clinician in establishing the correct diagnosis. Since the introduction of rheumatoid factor and antinuclear antibody (ANA) testing in the clinical practice, clinicians have increasingly used these tests to aid in the diagnosis of systemic connective-tissue diseases. Following the initial enthusiasm, it was later realized that their sensitivity and specificity varied significantly among different rheumatic diseases and that occasionally these autoantibodies could be detected in normal individuals. Furthermore, substantial variation in the reported results between different laboratories has been observed due to the lack of generally accepted standardized methods for their detection. Despite these limitations, the discovery of new autoantibodies that could aid in the understanding of pathogenesis and noninvasive diagnosis of complex autoimmune diseases should be viewed as a positive development towards the ultimate goal of providing the best of care to patients suffering from these potentially lethal diseases. This review will focus on the potential role and characteristics of the antineutrophil cytoplasmic antibodies (ANCA) in the pathogenesis and diagnosis of certain diseases.