Background NOVA View® is a new, automated digital image analysis system, which can be used for reading and interpreting anti-nuclear antibody (ANA) testing on HEp-2 cells, based on measured Light Intensity Units (LIU) and pattern recognition.
Objectives Our goal was to evaluate the analytical performance characteristics of the NOVA View®, with special attention given to precision, reproducibility and accuracy.
Methods Analytical sensitivity of the system was assessed by establishing the Limit of Blank (LoB) and Limit of Detection (LoD). Precision was evaluated on four specimens ranging from negative to 3+ positive, by running them in triplicates in 5 to 10 consecutive runs. Inter-instrument agreement was assessed by processing 11 specimens in various dilutions (n=38) and 9 controls on HEp-2 slides, and scanning them with two different instruments. Positive/negative cut-off was established on 200 random normal control samples based on percentile ranking and agreement with digital image reading. Endpoint titers as assessed from a single well by the NOVA View software were compared to results obtained from dilution series on the same specimens (n=20).
Results Samples are run on NOVA Lite® barcoded slides, providing positive patient identification from processing through interpretation. NOVA View results are expressed in LIU, and interpreted as negative or positive based on a pre-set cut-off. The detection limit of the system was established at 49 LIU, while the positive/negative cut-off at 66 LIU. The within-run and between-run coefficients of variation (CV%) of the strong positive specimen were 9.2 and 10.2%. The two week positive (around the cut-off) specimens produced 14.3% and 24.8% within-run CV%, and 21.1% and 27.0% between-run CV%. The negative specimen was consistently negative in all 30 replicates. Comparison of LIU values obtained on two different instruments showed tight correlation (R2=0.975) and only 4.1 LIU estimated bias (difference) at the cut-off level. Endpoint titers as assessed from a single well by the NOVA View matched with those obtained by testing dilution series in 9 samples, and were within ± one step in 9 specimens. In two specimens with nucleolar and homogenous patterns, respectively, the NOVA View endpoint titer differed from the manual titer with two dilution steps.
Conclusions Indirect immunofluorescence (IIF) testing on HEp-2 cells is considered the reference method for ANA detection.Lack of standardization of the manual method, however, still remains a concern.The NOVA View opens a new chapter of objective, precise, reproducible and quantifiable ANA detection, which could produce comparable results between laboratories. The stored digital images can be viewed and shared at any time, thereby promoting training and patient follow-up.
Disclosure of Interest G. Lakos Employee of: Inova Diagnostics, Inc., C. Buchner Employee of: Inova Diagnostics, Inc., C. Bryant Employee of: Inova Diagnostics, Inc., R. Rosenblum Employee of: Inova Diagnostics, Inc., P. Baker Employee of: Inova Diagnostics, Inc., V. Nelson Employee of: Inova Diagnostics, Inc., G. Granstedt Employee of: Inova Diagnostics, Inc., C. Melus Employee of: Systelab Technologies S.A., P. Martis Employee of: Inova Diagnostics, Inc., R. Burlingame: None Declared