Antinuclear antibodies (ANAs) are present in significant titers in individuals with systemic lupus erythematosus (SLE) and other connective tissue disorders. Their presence serves as a marker of disease and helps doctors diagnose the various connective tissue disorders in adults. According to a review published in Pediatric Rheumatology, the ANA test is greatly overused in children. In addition, positive results do not necessarily indicate that an autoimmune connective tissue disorder is present.
Blood Tests in Children
There are currently no blood markers that can identify risk factors for rheumatic diseases in children the way cholesterol levels are used to show cardiac disease risk in adults. For children with symptoms of arthritis, the C-reactive protein (CRP) test is a nonspecific marker of inflammation and may be beneficial. Otherwise, the blood test for Lyme disease is the only laboratory tests which fits the description of a true diagnostic test for arthritis. For a blood test to serve as a marker of disease, 9 out of 10 individuals with the illness should have positive results, and 9 out of 10 individuals without the disease will have negative results. The ANA test doesn’t have the degree of accuracy to recommend its use in the pediatric population unless patients have specific signs and symptoms of a particular connective tissue disorder, such as juvenile rheumatoid arthritis or SLE.
ANA Results and Patterns in Children
False positive ANA results are common. In one study of 138 children with positive ANA results, one-third of the subjects did not have a connective tissue disorder. In a similar study only 55% of the children with a positive ANA test result had an inflammatory rheumatic disease, and typically the titer was greater than 1:640. In a study from the British Columbia’s Children’s Hospital, researchers concluded that an ANA as high as 1:160 in children had little or no diagnostic value. In children found to have connective tissue disorders, the titer was much higher. In children with juvenile rheumatoid arthritis, the ANA test is more likely to be positive when uveitis is also present.
Children with a positive ANA who didn’t have a rheumatic disorder were not found to have a high risk of developing a rheumatic condition in the future. Although there is evidence that a positive ANA can precede the development of disease in adults by several years, studies showed that positive ANA results in children without a rheumatic disease had less than a 1% risk of developing a rheumatic disease within the next 61 months. However, the researchers noted that a positive ANA was found to precede idiopathic thrombocytopenic purpura (ITP), an autoimmune platelet disorder, in some children.
The study concluded that because of it’s high false positivity rate, the test should be limited to cases in which SLE, mixed connective tissue disease or other conditions are strongly suspected. In these cases, a positive ANA result can be used to confirm the diagnosis. When the test is performed as a screening tool, results below 1:640 should be ignored.
Besides being seen in connective tissue disorders, antinuclear antibodies can also occur in infection, malignancy and as a result of various drugs in conditions of drug-related lupus. In these conditions, symptoms resolve when the offending drug is stopped. Environmental toxins can also cause a positive result.
In their study the researchers found that children with SLE and other connective tissue disorders were more likely to have a homogenous pattern with mitotic staining. Children with results showing a nucleolar pattern of staining were unlikely to have a rheumatic disease.
Source
Petern Malleson, Murray Mackinnon, Michaela Sailer-Hoeck, and Charles Spencer, Review for the Generalist: The antinuclear antibody test in children—when to use it and what to do with a positive result, Pediatric Rheumatology, October, 2010.
Elaine Moore - I'm a retired medical technologist and medical writer with more than 30 years experience working in hospital laboratories. Currently, I ...
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