PORTLAND, ORE. – Joint pain isn’t usually part of the clinical picture when children have juvenile idiopathic arthritis, according to pediatric rheumatologist Victoria Cartwright.
"In fact, it helps you discount that juvenile arthritis is going on," she said at a conference sponsored by the North Pacific Pediatric Society.
Pain as an isolated complaint has a negative predictive value for pediatric rheumatic disease of 0.99 and, as one of several reasons for a rheumatology referral, a negative predictive value of 0.91 (Pediatrics 2002;110:354-9).
Dr. Victoria Cartwright
"That’s better than any lab test or x-ray [and] about as good as MRI. [So] if you’re calling me saying that Johnny has knee pain, I’m not as worried about JIA [juvenile idiopathic arthritis]. I may be worried about [Henoch-Schönlein purpura (HSP)] or a mechanical issue or something else ... but [not] JIA," said Dr. Cartwright of Randall Children’s Hospital at Legacy Emanuel in Portland, Ore.
On the other hand, "labs really don’t help one way or the other to make the diagnosis of arthritis. Rheumatoid factor doesn’t help. [Erythrocyte sedimentation rate] is helpful if it’s abnormal, but only kind of. I can have a kid who has 20 inflamed joints and their sed rate is 2; I can have another kid with one swollen knee, and their sed rate is 30. [However,] if the sed rate is over 100, I worry about other stuff," such as systemic disease, lupus, HSP, vasculitis, or malignancy, she said.
If those problems have been ruled out, Dr. Cartwright said she usually waits until kids have been on NSAIDs – she favors weight-dosed ibuprofen or naproxen – for a month before getting a complete blood count, a liver enzyme panel, and an antinuclear antibody (ANA) test. "I’m not a big fan of labs up front" for JIA "because we end up chasing the lab illness a little bit," she said. JIA kids also need a referral to an ophthalmologist to check for iritis. If this condition is present, ANA testing helps tell how aggressive it is.
As for assessment, Dr. Cartwright noted that obesity makes it tough to check the ankle for swelling; extra pounds obscure the Achilles tendon and the divots to either side. "It’s one of the joints I image a lot with MRI because I [often] can’t see it very well," she said.
Swelling can be hard to detect in kids with polyarticular disease because it can be more or less even on either side of the body, and, thus, less noticeable. One trick, especially helpful with the hands, is to compare the skin folds and wrinkles around corresponding joints. If they aren’t symmetrical, it could be due to swelling.
Check for jaw arthritis, too, Dr. Cartwright said. A lot of children don’t even know there’s a problem because it’s painless, but left unchecked, jaw arthritis can cause growth abnormalities – associated asymmetries are most obvious when the head’s tilted back – and make it difficult to fully open the mouth.
Patients should be able to insert their three middle fingers vertically into their mouth. When they can’t, "we do some dynamic stretching. We’ll stack tongue blades" to reach the appropriate thickness and have patients place them in their mouth to "stretch the muscles out, kind of like doing [physical therapy]," Dr. Cartwright said.
She said she has no relevant financial disclosures.