Case 2: Case Studies from the week of Jan 11th, 2016

The pattern of the rash and arthritis indicate that the patient has systemic lupus erythematosus (SLE). Classically the patient with SLE is a young woman with some, but not necessarily all, of the following presenting features: a butterfly-shaped rash over the face, fever, pain but no deformity in one or more of the peripheral joints, pleuritic chest pain, and photosensitivity. Patients with SLE are also susceptible to blood dyscrasias (such as hemolytic anemia and thrombocytopenia), renal pathology, oral ulcers, and a discoid rash. The serum antinuclear antibody (ANA) test is positive in nearly 100% of patients with SLE. Therefore, ANA is highly sensitive for SLE, but is not as specific for this disease making it a good initial screening test. ANAs are also commonly found in patients with CREST syndrome (limited scleroderma), Sjögren's syndrome, rheumatoid arthritis, mixed connective tissue disease (also known as Sharp's syndrome), and polymyositis.
ArthritisThrombocytopeniaPolymyositisLupus Erythematosus, SystemicPleuritic painOral UlcerScleroderma, LimitedRheumatoid ArthritisMixed Connective Tissue Disease
A is not correct. 5% chose this.
The serum ANA test is highly sensitive but not as highly specific for SLE and is routinely used as an initial screening test.
B is not correct. 20% chose this.
Both elevated anti-double-stranded DNA as well as anti-Smith antibodies are highly specific for SLE but not very sensitive. This means that while SLE cannot be ruled out with a negative result, there are few false-positive results, and both are good confirmatory tests for SLE.
C is not correct. 20% chose this.
Elevated anti-double-stranded DNA antibodies are highly specific for SLE but not very sensitive.
E is not correct. 6% chose this.
The serum ANA test is highly sensitive but not as highly specific for SLE and is routinely used as an initial screening test.

Bottom Line:
Serum antinuclear antibodies are a sensitive marker for SLE and thus a great screening test because there are few false-negative results.