Italian Multicentre Study for Application of a Diagnostic Algorithm in Autoantibody Testing for Autoimmune Rheumatic Disease: Conclusive Results

Aim: The presence of specific auto-antibodies in serum (i.e., antinuclear antibodies or ANA, anti-extractable nuclear antigens or anti-ENA, and anti-double stranded DNA or anti-dsDNA ) is one of the major criteria in the diagnostics of Autoimmune Rheumatic Disease. As such, the request for these tests has grown exponentially in laboratory practice. The aim of this study is to describe the implementation of a joint laboratory-clinics guideline for reducing clinically inappropriate requests for autoantibody testing in a broad geographic area (Parma, Modena, Piacenza, Reggio-Emilia) for the diagnosis of Autoimmune Rheumatic Disease.

Methods: This study, supported by a Regional grant for innovative research projects started in January 2008, is an observational research aimed at comparing the number of ANA, anti-dsDNA and anti-ENA testing as well as the percentage of positive test results before and after implementation of the diagnostic algorithm in hospitalized patients. A multidisciplinary team consisting of clinical immunologist and laboratory scientists was established, with the aim of collecting and analysing diagnostic criteria, clinical needs, laboratory report formats, analytical procedures, as well as the number of tests performed. The laboratory results and the clinical protocol were both validated by data emerging from the clinical follow-up studies.

Results: A joint guideline for auto-antibody testing, placing ANA test at the first level, has been developed and implemented since January 2009. The results for the period January-June 2009 (12,738 tests) were compared with those of the same period in 2008 (13,067 tests). A significant reduction in the number of anti-dsDNA (-26%) and anti-ENA (-15%) was observed. The percentage of second-level tests positivity after implementation of the diagnostic protocol had also consistently increased for both ENA (13% vs 17%) and dsDNA (9% vs 11%).

Discussion: The development and implementation of algorithms for the diagnostics of Autoimmune Rheumatic Disease in hospitalized patients was associated with a reduction in the number of second-level tests, but also with an increased diagnostic specificity. This outcome attests that close collaboration and audit between clinicians, laboratory specialists and healthcare services is effective to develop efficient diagnostic algorithms for both hospitalized patients and outpatients.