Choosing Wisely in Immunology Laboratory: Reviewing of Antinuclear Antibody (ANA) Test Requests and Results Together with Other Tests

In this study, it was aimed to examine the distribution and positivity rates of the tests reported in the medical immunology laboratory of a tertiary education and research hospital, and to determine the distribution of antinuclear antibody (ANA) test requests, which constitute a significant part of the workload, according to disease diagnosis/preliminary diagnoses and clinical departments, and to examine the possible causes and costs of incorrect-inappropriate test orders, and to consider effective and applicable solution suggestions. In the study, a retrospective review of data on all immunoserology tests (n=94,954 individual parameters) reported approximately over a three-year period starting from September 2016 was presented. When the tests are divided into three main groups; among all test parameters, ANA tests ranked first with a rate of 20.3% (n=19,248). In our study, the positivity rate of ANA tests evaluated by the indirect immunofluorescence antibody (IFA) method was found as 23.1% (n=4,446). The number of reported parameters of specific autoantibody tests (second group), which include many different tests (IFA, ELISA, and immunoblot based), was 67,976, and the overall positivity was 2.96%, varies between 0.8% and 12.7%, depending on the antibody type. In the ELISA-based brucella and antiviral (herpes simplex virus 1 and 2, varicella virus, measles virus, mumps virus, parvovirus B19) IgM and IgG antibody tests in the third group, the highest positivity rate was observed according to the number of tests requested (30.1%, 2,324/7,730). In ANA-positive patients, the most frequently detected ANA-related autoantibodies were anti-dsDNA (9.2%) and anti-SS-A (8.2%). In ANA-negative patients, in simultaneously ordered tests, anti-dsDNA positivity was found to be 3.3%, while positivity rates for other ANA-related specific autoantibodies were in the range of 0.0-0.31%. ANA tests were most frequently ordered from the rheumatology department (34.2%), and also the highest ANA positivity rate (28%) was observed in this unit. The most notable reason for unnecessary test ordering was the test requests by different physicians for the same patient. We consider that evaluation of ANA tests at a dilution of 1:100 may lead to unnecessary second-step testing (specific autoantibodies) due to the low positive results, and that narrow-scope second-step autoantibody test panels will have negative effects on laboratory efficiency.