Critical appraisal of the pattern of antinuclear antibodies (ANA) testing requested over a six month period at the "Escola Paulista de Medicina" (EPM), São Paulo.

Abstract

In order to evaluate the pattern of ANA testing solicitation, 506 patients with ANA testing requested from July 1st. 1988 to December 31st, 1988, had their charts reviewed. These patients, randomly selected, were regularly attending the outpatient clinic at the "Escola Paulista de Medicina" (EPM). 289 patients were followed up at the Rheumatology Division (group A) and 217 patients at other clinical divisions at EPM (group B). The diseases that most frequently motivated the request for ANA test were: group A--SLE (22.5%), RA (18.0%), undefined arthropathies (6.2%), PSS and CREST (5.9%) and Raynaud phenomena (5.5%); and group B--rheumatic diseases (24.4%), nephropathies (17.1%), neuropathies (16.6%), dermopathies (7.8%), hemopathies (4.6%), pneumopathies (4.2%) and ophthalmopathies (3.7%). The positivity of ANA test in groups A and B was 32.9% and 17.5% respectively. 94 SLE patients were clinically diagnosed. The positivity of ANA and anti-dsDNA tests in this group was respectively 85.1% and 26.6%. The sensitivity and specificity of 1982 ARA revised criteria were 94.7% and 99% respectively. The likelihood ratio (LR) of a positive or a negative test was established for this population. LR of a positive test was 6.5 while for a negative test it was 0.17. The ANA test, although lacking specificity, has been commonly requested by different specialties in order to practically rule-out the diagnosis of some connective rheumatic diseases. Immunofluorescence technique (IF) using antibodies conjugated with fluorochromes. was first described by Coons et al. in 1941. This method has been used as an important diagnostic tool in routine laboratory tests ever since.(ABSTRACT TRUNCATED AT 250 WORDS)