<prompt> A 23 yr. old female came with arthritis, Malar rash, oral ulcers, serositis pleuritis or pericarditis. The likely investigation to be positive isAnti nuclear antibodyAnti collagen antibodyAnti epithelial antibodyAntigen antibody complexes  <response>: A Anti nuclear antibody Antinuclear antibody ANA tests are positive in 5 to 10 percent of the general population, a rate that increases with age. Thus, given a one in 20 frequency for ANAs and a one in 2,000 frequency for systemic lupus erythematosus, only one in 100 persons with a positive ANA test will have the disease. Consequently, positive ANA test results must be interpreted with caution. Given the high sensitivity of the currently used substrate for testing, a negative ANA test essentially rules out systemic lupus erythematosus. 