ReviewA comparative study on the reliability of an automated system for the evaluation of cell-based indirect immunofluorescence
Introduction
Autoantibodies (AAB), in particular ANA, ANCA, and dsDNAab play a pivotal role in the serological diagnosis of systemic rheumatic and autoimmune liver diseases [1], [2], [3], [4], [5], [22], [23], [24], [25], [26]. Autoantibody assessment may help monitor disease activity, sub-classify and predict autoimmunity [6], [7], [8]. Indirect immunofluorescence tests are currently recommended as screening tests for ANA, complimentary tests for ANCA assessment, and confirmatory for dsDNAab detection [2], [9], [10], [11], [12], [13]. According to the recent recommendations of the American College of Rheumatology (ACR) ANA Task Force, IIF ANA tests should be considered the gold standard in ANA testing [10]. To meet modern laboratory standards, high reproducibility and accuracy of IIF reading are however required. Moreover, due to the growing request of trained technicians, autoantibody detection is becoming challenging, especially in large laboratories performing high volume of testing.
The introduction of digital imaging of IIF along with the development of automated interpretation systems for the assessment of AAB by IIF has paved the way to overcome important drawbacks of IIF interpretation, such as the subjective visual interpretation and the unsatisfactory reproducibility of results among different clinical laboratories [14], [15], [16]. The automated IIF interpretation system AKLIDES has been evaluated for ANA detection on HEp-2 cells, dsDNAab on C. luciliae, and ANCA on human neutrophils (i.e., AKLIDES), and was previously found to be reliable for the positive/negative differentiation of IIF patterns as well as for the pattern recognition of ANA and ANCA findings [15], [17]. The aim of the present study was to evaluate the performance of this fully automated IIF interpretation system in routine diagnostics and compare it with the visual expert interpretation of IIF.
Section snippets
Serum samples
A total number of 272 serum samples from patients with suspected autoimmune disease were collected from March to April 2011 for ANA (n = 182), dsDNAab (n = 44) and ANCA (n = 46) testing. The samples for ANA testing were either selected from random routine samples (n = 66), or specifically from patient samples previously known to be positive for autoantibodies (n = 116). All samples were collected in the clinical laboratories of the Academic Hospital of Parma and the General Hospital of Modena from
ANA testing
In total, 66 routine samples and 116 selected samples with known AAB levels have been analyzed to assess the performances of the AKLIDES system regarding positive/negative discrimination. Nine out of the 66 routine samples showed a discrepant reading comparing AKLIDES and visual interpretation by experts (Table 1). Eight of the discrepant samples were classified as weak speckled positive by AKLIDES and negative by visual examination. As such, only one case was really discrepant, i.e., negative
Discussion
The assessment of AAB by IIF is essential for the serological diagnosis of autoimmune disorders, but is in general characterized by a high degree of manual procedures, low throughput, and subjective interpretation [1], [4], [15]. Automation of autoantibody IIF reading including pattern recognition could therefore help reducing intra- and inter-laboratory variability. In particular, it would meet the growing demand for cost-effective assessment of large numbers of samples (i.e., high
Take-home message
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The introduction of an automated IIF interpretation system in routine Lab may offer new skills to the expert to screen and to modify the working strategy.
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