Technique-related variation in results of FANA tests.

We compared the reliability and reproducibility of three tests for fluorescent antinuclear antibodies (FANA) that are routinely performed in our laboratory. Sera from 72 patients, selected according to diagnosis (SLE in 28, RA in 12, and other connective-tissue diseases in 33), and from 32 healthy controls were tested with all three assays. There were wide variations between the results obtained with these tests. The variations did not reflect sensitivity or degree of standardisation (reproducibility on retesting was greater than 95%) and appeared to be inherent in the techniques. Clinicians should be aware of the technique-related differences in FANA assays.