Tests to Diagnose and Monitor Juvenile Arthritis
Blood and imaging tests help doctors find the cause of joint pain in children.
By Stephanie Watson | June 17, 2022
Joint soreness can have several possible causes in children, including injuries and overuse from sports and other activities. But if your child’s joints have been swollen, stiff and sore for a few weeks and you can’t find an obvious cause for these symptoms, it’s time to see a pediatrician or pediatric rheumatologist.
The most common form of juvenile arthritis (JA) is juvenile idiopathic arthritis (JIA), and there are a number of subtypes, which may have varying symptoms and effects, even beyond joints. These range from the number of affected joints to whether skin is affected. No single test can diagnose JIA. To get a diagnosis, the doctor will ask questions, examine your child, and order a few tests to rule out other conditions that cause similar symptoms, like infections, Lyme disease or lupus.
A combination of exams and tests can help the doctor figure out if your child has arthritis, and if so, which type.
The process starts with a health history. Expect your doctor to ask questions about your child’s symptoms, including when they started. Some JIA symptoms may not be obvious, so make sure to tell your doctor if your child
- Feels stiff in the morning when they wake up
- Avoids activities because of joint pain
- Has trouble with fine motor skills like writing with a pencil
- Has been running a fever
- Has swollen joints
The doctor might also ask whether anyone else in your family has inflammatory arthritis. This condition tends to run in families.
During the physical exam, the doctor might
- Check your child’s joints for swelling and pain
- Look for any problems with movement
- Feel their lymph nodes (glands) and belly for swelling or pain
- Shine a light into your child’s eyes to look for eye problems
- Check your child’s skin for rash or other abnormalities
JIA, and sometimes its treatments, can cause eye inflammation called uveitis and other eye problems. Children will need regular eye exams from an ophthalmologist, who will use a slit lamp to look for signs of inflammation.
These tests help your child’s doctor confirm the diagnosis and rule out other conditions that have similar symptoms.
Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP)
JIA is an inflammatory disease. Both erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) tests detect inflammation in the body. ESR measures how quickly red blood cells called erythrocytes fall to the bottom of a tube of blood. The higher the sedimentation (sed) rate, the more inflammation there is in your child’s body. C-reactive protein (CRP) is a substance the liver releases when there is inflammation in the body. These tests can’t definitively diagnose JIA because infections and other conditions can also cause inflammation. But they can at least point to the problem. Doctors also use these tests to monitor children’s response to treatment.
Antibodies are proteins our bodies make to protect us against germs and other invaders. Testing certain antibodies helps doctors diagnose JIA. Antinuclear antibodies (ANAs) are only found in the blood of people who have autoimmune diseases like arthritis. Children who test positive for ANAs are at higher risk for eye inflammation and need to see an ophthalmologist.
Rheumatoid Factor (RF)
Rheumatoid factor (RF) is an antibody found in the blood of people with rheumatoid arthritis and other rheumatoid diseases. An RF blood test can show whether a child with polyarticular JIA, a type that affects five or more joints, has this antibody (RF-positive) or doesn’t have it (RF-negative). JIA cases that are RF-negative are called “seronegative,” indicating that the blood marker for inflammation, RF, is not present.
Anti-cyclic citrullinated peptide (CCP)
This test looks for antibodies called cyclic citrullinated peptide (CCP) in the blood. These antibodies are a sign of rheumatoid arthritis. In children, they can mean the arthritis is more severe.
Human Leukocyte Antigen B27
HLA-B27 is a protein found on the surface of white blood cells. It helps the immune system tell the difference between healthy cells and foreign ones. Some children who test positive for HLA-B27 have enthesitis-related JIA, meaning that the site where cartilage attached to bone at the joint is involved.
Other Blood Tests
The doctor might also do a complete blood count (CBC) or other blood tests to check the number of white blood cells, red blood cells and platelets. People with inflammatory arthritis often have low red blood cells, a condition called anemia. A high number of white blood cells is a sign of infection. Blood tests may also be done to check liver and kidney function before and after children start on medication, because some JIA treatments can harm these organs.
These tests monitor how well the kidneys are working. Blood or protein in the urine is a sign these organs aren’t functioning properly.
These tests let the doctor see your child’s joints to look for signs of damage from JIA. Imaging tests are also useful once your child has started on treatment, to show whether the medication they’re taking is helping to slow joint damage.
X-ray. This test uses a small amount of radiation to create images of joints and other structures inside the body. It may be the first test the doctor does, because it can show signs of infection or injury to rule out those problems. Later, an X-ray can show signs of damage to the joints.
Ultrasound. This imaging technique uses sound waves instead of radiation to produce images from inside the body. It’s more sensitive than X-rays at picking up joint inflammation and damage early in the course of the disease.
Computed Tomography (CT) Scan. Computed tomography (CT) takes a series of X-rays from various angles and combines them into one cross-sectional image. A CT scan can show the bones in greater detail than an X-ray.
Magnetic Resonance Imaging (MRI). This imaging technique uses strong magnets and a computer to take images of the organs and tissues. An MRI can reveal inflammation and rule out other conditions like fractures or infection.
Monitoring Your Child’s Progress
Once your child has been diagnosed and treatment has started, their doctor will monitor them at regular intervals to check that the treatment is working and to make sure their arthritis isn’t getting worse. These visits might include an exam of the joints, and possibly blood and imaging tests.
If joint damage is progressing or your child has side effects from treatment, the doctor might raise or lower the medication dosage, switch your child to a different drug, or add another medicine. Because medications like methotrexate, nonsteroidal anti-inflammatory drugs (NSAIDs), and biologics can be hard on the liver and kidneys, kids who are on these treatments will need regular blood and urine tests to check for liver and kidney damage.
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