ACR ABSTRACT - Assessing the ANA test as a screening tool: utility or futility?

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[1845] - Assessing the ANA Test as a Screening Tool: Utility or Futility?

Aryeh M Abeles, MD1,Micha Abeles, MD1. 1University of Connecticut Health Center

Introduction: Current ANA testing may be overly sensitive, resulting

in frequent false positives as well as unnecessary follow-up testing

and misdiagnosis. Several studies have focused on ANA prevalence and

predictive value, but the purpose of this investigation was to

evaluate the clinical utility of a positive ANA test in a real-world

setting, by reviewing the outcomes of patients referred to a tertiary

rheumatology clinic for evaluation of a positive ANA test. No prior

study has directly addressed this question.

Method: We reviewed records for all consultation patients presenting

to the authors at the UCHC rheumatology clinic between July 2007 and

July 2009. Patients were included in the evaluation if they had been

referred for a positive ANA. Patients presenting with an

already-diagnosed ANA-associated rheumatic disease (AARD) were

excluded. All ANA tests and all referrals had been ordered by

non-rheumatologists. A complete review of systems and physical

examination was performed on each patient. 91 out of 101 patients with

ANA titers ≥1:320 had the following labs drawn: antibody (Ab) panel

(Anti-dsDNA, SSA/SSB, Sm, RNP), C3, C4, CH50, CBC, and ESR. Of 67

patients with ANA ≥1:640, 64 had lab evaluations performed as above.

Referring physician reasons for ordering ANA testing were also

collated.

Results: Of 1,306 initial consultation visits to our clinic, 232 were

referrals for a positive ANA, with titers ranging from 1:40 to greater

than 1:5120. Initial ANA testing had been performed at several

different laboratories (the majority at UCHC). 98% of all initial ANA

tests had been run using immunofluoresence assay with Hep-2 cells.

9.1% of patients evaluated (21/232) had an AARD (5 SLE, 12 Sjogren's

syndrome, 3 scleroderma, 1 MCTD). The remainder of patients had no

AARD, of whom twenty-one (9.1%) had isolated autoimmune thyroid Ab

present. No patient with an ANA ≤1:80, and only 1 patient with

ANA≤1:160, had a rheumatic disease. There was no correlation between

the highest ANA titers with a specific rheumatic illness. The most

common reason for ordering ANA testing was widespread pain and

tenderness (54/232, 23.2%) but also included, among others, chronic

lower back pain, episodic chronic rhinitis, palpitations, thinning

hair, unilateral heel pain, and lateral buttock pain. The positive

predictive value of an ANA test in our cohort of patients was 2.2% for

lupus and 9.1% for any AARD.

Conclusion: In this retrospective study, over 90% of patients referred

to a tertiary rheumatology clinic for positive ANA testing had no

evidence of an AARD. The poor predictive value of a positive ANA test

may in part be attributable to poor patient selection with concomitant

low pretest probabilities. The extremely low positive predictive value

of ANA tests at titers below or equal to 1:160 suggests that the

cutoff of a “positive†ANA may need to be re-evaluated by testing

laboratories. Even at high titers, however, many patients referred for

a positive ANA had no discernible AARD, corroborating previously noted

lack of predictive value of ANA testing.

Wednesday, November 10, 2010, 9:00 am

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