<prompt> A young girl is admitted with joint pains and butterfly rash and positive urine proteinuria. The best test for her diagnosis is ?Anti ds-DNA antibodyAnti-centromere antibodyAntibodies to RNPAntibodies to tRNA synthetase  <response>: Ans. is a i.e., Anti ds-DNA antibody o Association of antibodies with disease activity. Anti ds-DNA antibody is-increased risk oj nephritis in cases oj SLE. Anti centromere ab is-limited scleroderma. Antibodies to RNP is-CNS lupus. Antibodies to tRNA synthetase-polymyositis with interstitial lung disease. 