Variation in ANA titres in Auckland

Abstract

Aim: To determine the intralaboratory and interlaboratory variation in reported ANA titres in three Auckland laboratories, and to see if this has improved since a similar study was performed in 1981.

Methods: Serum samples on 26 subjects with rheumatological symptoms were sent to the three laboratories on two separate days in 1993, and the presence and titre of ANA determined.

Results: The number of titre dilutions by which duplicate samples differed within each laboratory has decreased since the previous study, and variation within each laboratory of greater than two dilutions was not observed. The correlation between the laboratories has improved since the previous study, particularly for Lab A vs. Lab B.

Conclusion: The ANA test, as expressed in titres, is more reproducible in Auckland laboratories than has been the case in the past.