in part, because of a positive ANA test were no more likely to have a chronic inflammatory disease than children with a negative test.
In another study from a pediatric rheumatology clinic, only 55% of all of the children with a positive ANA test had an inflammatory rheumatic disease. Positive antibodies to double-stranded DNA or to extractable nuclear antigens (Sm, RNP) indicating SLE or MCTD were strongly correlated with an ANA titer ≥1:640. The authors recommended therefore, that these more specific tests be performed only if the child had a positive ANA test at high titer .
McGhee and colleagues reviewed the ANA titer clinical utility in 2004 . One hundred and ten children were evaluated who had been referred for a positive ANA. Of the 110, 10 subsequently were found to have SLE, 18 had JRA, 1 had MCTD, and 1 had Raynaud's phenomenon. Neither a positive ANA neither titer nor the degree of positivity of the ANA helped pick out the children with SLE from the children without a chronic inflammatory disease. Tellingly, it wasn't the elevated ANA titer that distinguished the children with JRA from those with other musculoskeletal problems, but the history (e.g., morning stiffness) and the physical exam (e.g., presence of rash, swollen joints).
All these studies demonstrate that a positive ANA test is found frequently in a pediatric hospital population, and even in high titer has only a poor ability to determine whether a child has an inflammatory rheumatic disease.
Development of rheumatic diseases in ANA positive individuals
It could be argued that the finding of a positive ANA test indicates that the child has an occult disease that will become manifest later. Is there any evidence to support or refute this?
There is some evidence that ANA may sometimes precede the development of SLE by several years. Using Finland's Social Security Institution's population registry, Aho et al.  were able to trace 16 serum samples from apparently healthy subjects who later developed SLE or MCTD. Ten of the 16 (62.5%) samples were positive for ANA. Eight of the 11 (72.7%) were positive when the interval from sampling to onset of first symptoms was ≤ 2 years and 2 of 5 cases (40%) were positive when the interval was > 3 years. Based on an incidence rate of lupus of 5/100,000/year, the authors calculated that lupus would develop in less than one percent of the ANA positive individuals. Cabral et al.  followed the course of 24 children who were considered clinically not to have an inflammatory disease despite being ANA positive and found that no patient developed an overt inflammatory disease during a follow-up period of 61 months (range 13 to 138 months).
Some studies have evaluated the outcome in patients with fibromyalgia. Fibromyalgia is a musculoskeletal pain condition not thought to be an autoimmune disease. Interestingly, some fibromyalgia patients are also ANA positive, but there has been no evidence that the occurrence of a positive ANA influences patient outcome. Al-Allaf et al.  found the ANA positivity rate (titers not given, a positive result was simply defined as "plus") in their adult patients with fibromyalgia was 8.8%. This rate was almost identical to the 8.9% ANA positivity rate in their control patients with osteoarthritis. The 12 individuals who had fibromyalgia and were ANA positive were matched for age and sex with 12 ANA negative patients. Over a 2-4 year follow-up period one patient in the ANA positive group fulfilled criteria for SLE, and one in the ANA negative group fulfilled criteria for Sjögren's syndrome. The authors concluded that the ANA test (at least in low titer) was not a good predictor of future connective tissue disease.
In a separate study of 59 pediatric patients with fibromyalgia, 17 (28.8%) were ANA positive (mean titer 1:160). Fifty patients were followed for a mean of 18.3 months and during that time no patient developed a connective tissue disease . We would conclude from these findings that only rarely is the presence of ANA the harbinger of occult SLE or another connective tissue disease.
ANA 