Clarification of suspected rheumatic symptoms is mainly achieved by the serological assessment/detection of disease-specific autoantibodies (e.g., anti-nuclear antibodies, ANAs).

Despite the development of enzyme-linked immunosorbent immunoassay (ELISA) and other alternative methods or technologies, screening for ANAs by IIF assays remains the gold standard method in the current diagnostic approach to systemic rheumatic disorders such as systemic lupus erythematosus (SLE), Sjögren’s syndrome (SS), progressive systemic sclerosis (PSS), dermatomyositis-polymyositis (DM/PM) or mixed connective-tissue disease (MCTD).

International guidelines recommend that ANA screening be performed on human epithelial (HEp-2) cells. Other cell substrates such as Crithidia luciliae (for the detection of autoantibodies to dsDNA) and human granulocytes (for the detection of anti-neutrophil cytoplasmic autoantibodies, ANCA) are routinely employed in cell-based IIF procedures.

Since autoantibodies produce characteristic fluorescence patterns whose analysis depends on the knowledgeability and the subjective interpretations of investigators, high intra- and interlaboratory variability represents a major problem in autoimmune diseases diagnostics.

The increase in workload and the need for standardized and reproducible evaluation of cell-based IIF assays have
guided autoimmunity laboratories on the road to automation.

The new Zenit G Sight system from A. Menarini Diagnostics was specifically designed to overcome IIF-specific issues, making it particularly suited for the automated serological diagnosis of autoimmune diseases in a routine laboratory setting.

The principal steps of the method are:

1. Serum sample dilution (for example 1:80) and incubation with substrate fixed on glass slides for 30 min in a moisture chamber at RT
2. Incubation with fluorescein isothiocyanate (FITC)-conjugated sheep anti human Ig for 30 min at RT
3. Assessment: visual or automated analysis of slides

ANA detection on HEp-2 cells generates specific fluorescence patterns. The five main patterns which can be found are the following

* ANA fluorescence patterns on HEp-2 cells are shown because this is the most widely used test for visual/automated screening of rheumatic diseases

IIF assay is a low-cost, simple and rapid method for routine autoimmune screening; however, it has several disadvantages, which can be easily resolved with Zenit G Sight.

• Subjective analysis
• Limited number of samples
• Time-consuming sample screening
• Fluorochrome decay
• Organized archiving space required
• Difficult to exchange results with other labs

• Objective quantification and pattern recognition
• High workload management
• Efficient automated +/- sera discrimination
• Digitized image data
• File storage and easy retrieval of previous reports
• Online access and data exchange

• Valuable and accurate
  giving clinicians a precious aid for diagnosis by providing a full quantitative/qualitative report on autoantibody serological status
  
  
• Reliable
  providing results that are reproducible and comparable within and between laboratories
  
  
• Cost-effective
  alleviating the heavy workload of laboratories with large sample numbers, maximizing efficiency and optimizing human resources
  
  
• Secure
  safeguarding results and improving data management