The tendency in interpretation of ANA results (by reading the slides) is to overread and call negative samples positive. Most frequently this is caused by staring too long at the cells, using too high of a magnification, and an understandable desire to detect all true positives. With proper training reading the slides can be greatly simplified.
Follow these three steps:
- Look initially at 200x total magnification.
- An ANA positive sample must have a clearly discernable pattern in the nucleus of the interphase cells.
- Only use 400x magnification to confirm the pattern seen during initial the screen with 200x.
It is advised that the ANA slide first be viewed using 200x total magnification (20x objective with 10x oculars). During this first assessment you look for a clearly discernable pattern in the nucleus of the interphase cells. If no discernable pattern is seen the sample is ANA negative.
Do not stare at the magnified view too long--you could interpret patterns that are not present. Do not switch to a higher magnification just to see if you can identify something that isn't visible at 200x. If the sample looks negative at 200x, and you go to 400x and start thinking "I might be able to somewhat see a pattern," the sample is negative. It cannot be overemphasized that to be ANA positive there must be a clearly discernable pattern in the nucleus of the interphase cells.