Antinuclear antibody testing

In the clinical laboratory, the most commonly performed auto-antibody test is the one to detect antinuclear antibody (ANA). It provides the best sin-gle test to rule out the diagnosis of systemic lupus erythematosus (SLE) in children or adults, but it is also one of the most overordered tests in the lab-oratory [1,2]. Even though it has excellent sensitivity and reasonable speci-ficity, its positive predictive value in many clinical settings is awful because of its overuse in low-risk populations. Furthermore, the evolution of the tech-nique from the subjective (yet reasonably specific) lupus erythematosus (LE) cell preparation, to immunofluorescence ANA (ANA-IFA) performed on a variety of substrates, to the automated objective enzyme immunoassay (ANA-EIA) has added further confusion. Which of these assays do clini-cians receive when they order the ANA test that is listed on the laboratory requisition? In the past 5 years there has been a notable shift in the deploy-ment of ANA tests in the diagnosis of SLE. There are two main features to this shift. The first change involves an evolution from subjective to objective data, and the second change follows from the industry-wide effort to improve efficiency by switching from manual to automated procedures. Ben-efits of these changes are the lowered costs for ANA tests and the potential for improving the consistency of performance of the ANA test by providing objective data. The ready availability of this testing, however, may also encourage its overuse in low-risk populations, thereby diminishing its posi-tive predictive value. This article provides background on the current state of ANA screening, reviews the ongoing shift in technology for ANA serol-ogy, illustrates how overuse of ANA testing reduces its value, and empha-sizes the use of patient selection to improve its positive predictive value