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

RESUMO

In order to evaluate the pattern of ANA testing solicitation, 506 patients with ANA testing requested from July 1st. 1988 to December, 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 clincial divisions at EPM (group B). The disease that most frequently motivated the request for ANA test were: group A - SLE (22.5 per cents), RA (18.1 per cents), undefined arthropathies (6.2 per cents), PSS and CREST (5.9 per cents) and Raynaud phenomena (5.5 per cents); and group B - rheumatic diseases (24.4 per cents), nephropathies (17.1 per cents), neuropathies (16.6 per cents), dermopathies (7.8 per cents), hemopathies (4.6 per cents), pneumopathies (4.2 per cents) and ophtalmopathies (3.7 per cents). The positivity of ANA test in groups A and B was 32.9 per cents and 17.5 per cents respectively. 92 SLE patients were clinically diagnosed. The positivity of Ana and anti-dsDNA tests in this group was respectively 85.1 per cents and 26.6 per cents. The sensitivity and specificity of 1982 ARA revised criteria were 94.7 per cents and 99 per cents 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 specialities in order to practically rule-out the diagnosis of some connective rheumatic diseases. Immunofluorescence technique (IF) using antibodies conjugated with fluorchromes was first described by Coons et al. in 1941 (4). This method has been used as an important diagnostic tool in routine laboratory tests ever since. Anew technique using indirect immunofluorescence for detection of antinuclear antibodies (ANA) was developed by Friou in 1957 (5). This method has been gaing importance since then, due to the presence of antoantibodies in a variety of neoplastic, infectious, autoimmune and, particularly, connective tissue diseases. In 1960, the study of Anderson (1) led to the description of a new set of autoantibodies, which recognized extractable nuclear and citoplasmatic antigens in a great percentage of cases, but were not detected by indirect IF. Nowadays, these autoantibodies can be identified by immunodifusion, immunoenzymatic, radioimmune or immunoblot techniques...