Diagnosing
How do doctors detect juvenile rheumatoid arthritis?
Juvenile rheumatoid arthritis is difficult to detect and diagnose. But once
doctors give your child a diagnosis, treatment can start immediately.
Different types of juvenile rheumatoid arthritis have different symptoms,
while symptoms for the same types of JRA can vary from one child to another.
While there is no one specific test to indicate JRA, diagnosis is made, in
part, on the basis of your child's collection of symptoms. Because laboratory
tests for JRA often show normal results, diagnosis is made after looking
at your child's collection of symptoms. However, some nonspecific indicators
of inflammation may be elevated, including white blood cell count, erthrocyte
sedimentation rate, and a marker called C-reactive protein. As with many
chronic diseases, anemia may also be present.
A doctor makes a diagnosis of JRA by carefully examining your child from
head to toe, looking at the medical history of your child and your family,
and considering the results of laboratory tests and X Rays to help to rule
out other conditions. Children with extraordinarily early onset of JRA often
test positively for rheumatoid factors.
Symptoms of juvenile rheumatoid arthritis
Doctors suspect JRA (along with several other possible conditions) when they
see children with persistent joint pain, swelling, unexplained skin rashes,
fever, swelling of lymph nodes, inflammation of internal organs, and/or
an unexplained limp or excessive clumsiness.
The diagnosis is made after other possible illnesses are ruled out and after
various symptoms of JRA are present for at least six weeks. It is a good
idea to keep a record of your child’s symptoms, noting when they first
appear and when they become better or worse.
Laboratory Tests
Laboratory tests do not by themselves provide a clear diagnosis. They are
used to help rule out other conditions and to help classify your child’s
type of JRA.
While the following tests help diagnose JRA, in most cases, only a selection
are used.
- Antinuclear antibody (ANA): Measures blood levels of antibodies, which are often present in children with JRA. It is also useful in predicting if your child has an accompanying eye disorder.
- Arthrocentesis (Also called joint aspiration): A procedure which involves obtaining a sample of synovial fluid in the joint for examination by inserting a thin, hollow needle into the joint and removing the fluid with a syringe.
- Autoantibodies: Checks for certain antibodies. Antibodies are produced by the body to fight infection. Some antibodies that may fight parts of the body's own cells or tissues are called 'autoantibodies.' If your child has polyarthritis, the laboratory staff may check for rheumatoid factor (RF) to see whether he or she is RF - positive or negative.
- Blood culture: Detects bacteria that cause infections in the bloodstream. This may be done to rule out infections.
- Bone marrow examination: A test that allows doctors to look at blood where it is formed (in the bone marrow) to rule out conditions such as leukemia.
- Bone scan: Detects changes in bone and joints to evaluate the causes of unexplained bone and joint pain.
- Complement: Measures the level of complement, a group of proteins in the blood; low levels of complement in the blood are associated with immune disorders.
- Creatinine: A blood test to evaluate for underlying kidney disease.
- Complete blood count (CBC): A common blood test used to evaluate all the basic cellular components of blood, including red blood cells, white blood cells, and platelets. (High count of white cells and platelets causes inflammation). Abnormalities in the numbers and appearances of these cells can be useful in the diagnosis of many medical conditions.
- Computerized tomography scan (Also called a CT or CAT scan): A diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce cross - sectional images (often called "slices"), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x- rays.
- C-reactive protein (CRP): Measures concentrations of this protein in the blood as an indication of inflammation or disease activity.
- Erytrocyte sedimentation rate (ESR or sed rate): A measurement of how quickly red blood cells fall to the bottom of a test tube. When swelling and inflammation are present, the blood's proteins clump together and become heavier than normal; when measured, they fall and settle faster at the bottom of the test tube. Generally, the faster the blood cells fall, the more severe the inflammation.
- Hematocrit: Measures the number of red blood cells present in a sample of blood. Low levels of red blood cells (anemia) are common in children with inflammatory arthritis and rheumatic diseases.
- Liver function tests (LFT): Measures how well the liver is working.
- Magnetic resonance imaging (MRI): A diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.
- Rheumatoid Factor (RF): A test for rheumatoid factor, an antibody produced in the blood of children with some forms of JRA. It is much more commonly found in adults with rheumatoid arthritis.
- Urinalysis: Testing of a urine sample for protein, red blood cells, white blood cells, or casts to indicate kidney disease associated with several rheumatic diseases.
- White blood cell count (WBC): Measures the number of white blood cells in the blood (increased levels of white blood cells may indicate an infection, while decreased levels may indicate certain rheumatic diseases or reaction to medication).
- Urea and electrolytes (U&E): Measures how well the kidneys are working.
- X-ray: A diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film. X-rays are needed if your doctor suspects injury to the bone or unusual bone development. Early in the illness, some X-rays can show cartilage damage. In general, X-rays are useful later, when bones may be affected by the illness.
What other tests might my child have?
If your doctor suspects systemic arthritis, your child will
undergo several tests to rule out other illnesses, including a bone marrow
sample to rule out leukemia.
Doctors may also test for certain viral infections, such as Lyme disease,
that can cause similar symptoms or occur along with arthritis.
Why are eye tests important?
It is essential that regular eye exams are given to children with JRA, as
all are at risk of having inflammation in the eye (uveitis). While uveitis
is often painless and not normally noticed until damage has been done, regular
tests will detect it early on. If left untreated, uveitis can cause blindness – a
condition that is becoming increasingly rare.
If your child has oligoarthritis (in which four or fewer joints are affected
during the first six months of the disease) and the antibody test indicates
a risk of uveitis, the child should have regular eye exams. All children
should have their eyes checked as soon as possible after diagnosis of JRA,
and then when the ophthalmologist advises.
Eye exams are painless, although a bit uncomfortable. The ophthalmologist
will check general vision, then examine your child's eyes for signs of uveitis
using a special (slit lamp) microscope. The ophthalmologist may also enlarge
(dilate) the pupil to look at the back of the eyes.
If your child is diagnosed with uveitis, eye drops, some of which contain
steroids will treat the problem. When these drops are used, almost none of
the steroid is absorbed into the body. Other types of drops enlarge the pupil
to prevent the swollen iris from sticking to the lens; or to reduce the pressure
inside the eye. Most children with uveitis are treated successfully.
Other illnesses
