Table 2

Comparison of manual and automated positive/negative discrimination assessing fluorescence intensity of 342 samples on ethN and formN patterns.

ethN

Automated interpretation by AKLIDES™

n (%)

-

+/-

+

++

+++

++++

-

133 (38.9)

1 (0.3)

0 (0)

0 (0)

0 (0)

0 (0)

+/-

24 (7.0)

29 (8.5)

12 (3.5)

0 (0)

0 (0)

0 (0)

+

0 (0)

4 (1.2)

44 (12.9)

11 (3.2)

0 (0)

0 (0)

++

0 (0)

0 (0)

4 (1.2)

34 (9.9)

9 (2.6)

0 (0)

+++

0 (0)

0 (0)

0 (0)

3 (0.9)

16 (4.6)

5 (1.5)

++++

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

13 (3.8)

Visual interpretation

formN

n (%)

-

+/-

+

++

+++

++++

-

225 (65.8)

8 (2.3)

2 (0.6)

2 (0.6)

0 (0)

0 (0)

+/-

9 (2.6)

22 (6.4)

5 (1.5)

0 (0)

0 (0)

0 (0)

+

0 (0)

5 (1.5)

25 (7.3)

6 (1.7)

0 (0)

0 (0)

++

0 (0)

0 (0)

2 (0.6)

20 (5.8)

1 (0.3)

0 (0)

+++

0 (0)

0 (0)

0 (0)

1 (0.3)

6 (1.7)

0 (0)

++++

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

3 (0.9)

ANCA IIF patterns were first interpreted automatically with AKLIDES™ followed by manual reading with a routine fluorescence microscope. Both interpretation methods demonstrated very good agreement on ethN and formN (κ = 0.955, 95% confidence interval (CI): 0.944 to 0.965; κ = 0.929, 95% CI: 0.895 to 0.964; respectively). Quantitative fluorescence intensity threshold values for ethN: < 15 negative (-); ≥ 15 borderline (+/-) < 40; ≥ 40 weak positive (+) < 150; ≥ 150 positive (++) < 400; ≥ 400 strong positive (+++) < 700; ≥ 700 very strong positive (++++). Quantitative fluorescence intensity threshold values for formN: < 20 negative (-); ≥ 20 borderline (+/-) < 30; ≥ 30 weak positive (+) < 100; ≥ 100 positive (++) < 300; ≥ 300 strong positive (+++) < 600; ≥ 600 very strong positive (++++). ANCA, antineutrophil cytoplasmic antibody; ethN, ethanol-fixed neutrophils; formN, formalin-fixed neutrophils; IIF, indirect immunofluorescence.

Knütter et al. Arthritis Research & Therapy 2012 14:R271   doi:10.1186/ar4119