The ACR recommends ANA testing in patients who have two or more unexplained signs or symptoms listed in Table 2.2,20,21 [Reference2—Evidence level C, consensus/expert guidelines] Because of the high rate of false positive ANA titers, testing for systemic lupus erythematosus with an ANA titer or other autoantibody test is not indicated in patients with isolated myalgias or arthralgias in the absence of these specific clinical signs.45 Under most circumstances, a persistently negative ANA titer (less than 1:40) can be assumed to rule out systemic lupus erythematosus.41
Aggrecan is a type of protein known as a proteoglycan, which means it has several sugar molecules attached to it. It is the most abundant proteoglycan in cartilage, a tough, flexible tissue that makes up much of the skeleton during early development. Most cartilage is later converted to bone (a process called ossification), except for the cartilage that continues to cover and protect the ends of bones and is present in the nose, airways, and external ears. Aggrecan attaches to the other components of cartilage, organizing the network of molecules that gives cartilage its strength. These interactions occur at a specific region of the aggrecan protein called the C-type lectin domain (CLD). Because of the attached sugars, aggrecan attracts water molecules and gives cartilage its gel-like structure. This feature enables the cartilage to resist compression, protecting bones and joints. Although its role is unclear, aggrecan affects bone development.
In one study41 that used patients with connective tissue diseases as the control group, the revised ACR diagnostic criteria for systemic lupus erythematosus were found to have an overall sensitivity of 96 percent and a specificity of 96 percent. Other studies21,32,43 have reported sensitivities ranging from 78 to 96 percent and specificities ranging from 89 to 100 percent. The ACR criteria may be less accurate in patients with mild disease.21
ANA = antinuclear antibody; CNS = central nervous system; ds-DNA = double-stranded DNA; ELISA = enzyme-linked immunoassay; ENA = extractable nuclear antigen; Ig = immunoglobulin; p-ANCA = perinuclear antineutrophil cytoplasmic antibody; RBCs = red blood cells; RNP = ribonucleic protein; SLE = systemic lupus erythematosus; Sm = Smith; SSA = Sjögren syndrome A; SSB = Sjögren syndrome B.
In recent years, mycophenolate mofetil (CellCept) has been used as an effective medication for lupus, particularly when it is associated with kidney disease. CellCept has been helpful in reversing active lupus kidney disease (lupus renal disease) and in maintaining remission after it is established. Its lower side-effect profile has advantage over traditional immune-suppression medications.
Doctors are tasked with interpreting test results, then correlating them with your symptoms and other test results. It's difficult when patients exhibit vague symptoms and clashing test results, but skillful doctors can consider all of these pieces of evidence and eventually determine whether you have lupus or something else entirely. This may take some time along with trial and error.
“My message to patients is that we can do an excellent job of managing the condition compared to 20 years ago,” says Roberto Caricchio, MD, the interim section chief of rheumatology at Temple University Hospital in Philadelphia and the director of the Temple Lupus Clinic at the Lewis Katz School of Medicine. With that said, people should never underestimate the serious effects lupus can have, he adds, which is why working with your doctor to manage the condition is so important.
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