Is wide spectrum autoantibody testing cost-effective in the management of chronic urticaria (CU)?

Abstract

Background It is believed that a subset of CU is immune-mediated and, indeed, autoimmunity to thyroid specific antigens and high affinity IgE receptor has been described in a proportion of such cases. Aim To verify the occurrence of other autoimmune phenomena and to establish whether screening for a wide spectrum of autoantibodies is cost-effective in the diagnostic evaluation of this condition. Methods Sera from 184 patients with CU were tested by indirect immunofluorescence for antinuclear (ANA), anti smooth muscle (SMA), antimitochondrial (AMA) and anti liver and kidney microsomal (LKM-1) antibodies. A large subset of the same sera were tested by the same technique also for anti neutrophil cytoplasmic (ANCA) and antiendomysial (EmA) antibodies. Results LKM-1 was never detected and AMA was found in 1 case (0.5%). ANA (8.7%) and SMA (11.4%) were more frequently found than in healthy controls, though the difference was not statistically significant. Furthermore, titers were generally low: less than 1:80 in over 90% cases. Similar results were obtained with ANCA, which were found in 8% cases. None of the autoantibody positive patients has developed any autoimmune disorder so far. IgA EmA was found in 1 case (0.8%), who was histologically diagnosed as celiac and put on a gluten-free diet. Conclusions Wide spectrum autoantibody testing is not cost-effective in CU and is advisable only when there is a high clinical probability of underlying autoimmune disease or low cost laboratory facilities are available. In this latter case, we suggest to cut the screening dilution to 1:160 in order to increase the specificity.