Lab Testing and Juvenile Rheumatoid Arthritis

Juvenile rheumatoid arthritis (or JRA), which is also referred to as juvenile idiopathic arthritis (or JIA), affects 50,000 young people in the United States.  JRA and is the most common form of arthritis that is suffered by children. This condition affects children younger than 16 who suffer 6 weeks or more of persistent arthritis. Symptoms of JRA include stiffness, redness, swelling, pain, and joint inflammation. It may also cause internal organs to become inflamed, cause eye problems like uveitis, affect growth, and damage joints.  

JRA is thought to be a type of autoimmune disorder. Even though the susceptibility of developing JRA might be inherited, it is also thought that a triggering event is necessary in order for it to emerge. Not a lot is known about what might trigger JRA. That is why JRA is often referred to as being “idiopathic” (or no known cause).  

JRA classification systems can vary; however, the major types below may be included: 

Pauciarticular (or Oligoarthritis) constitutes around 50% of JRA cases. Four or fewer joints are affected and are usually large joints like the wrists or knees. Eye inflammation is associated with it as well.  

Polyarticular is where five joints or more are affected, particularly those in the hands and fingers. There are two types of polyarticular JRA: Rheumatoid factor (RF)-positive and (RF)-negative. RF-negative is found more often in girls than it is in boys, while RF-positive behaves similarly to adult rheumatoid arthritis.  

Systemic is the least common type of Juvenile Rheumatoid Arthritis. Numerous parts of the body are affected, including internal organs and joints. Children who have this systemic JRA might experience frequent rashes and fevers that can rapidly come and go.  

Psoriatic arthritis is a type of arthritis that is associated with psoriasis, which is a skin condition, in a child, parent, or sibling. Some professionals view this disease as being distinct from JCA. 

Enthesitis-related arthritis is found in the spine and lower extremities. 

Undifferentiated arthritis is arthritis that doesn’t fit in just one of the above categories; it could fit in none or more than one of the categories. 

Signs & Symptoms

Symptoms can vary from one child to the next and, over time, will often cycle between remissions and flare-ups. Symptoms might persist in some children, while in others, these same symptoms might disappear permanently.  

The symptoms can include:

  • Swelling
  • Joint Pain
  • Reluctance in wanting to move a joint that is affected
  • Limping
  • Morning Stiffness

Children who have systemic Juvenile Rheumatoid Arthritis might have swollen lymph nodes, rash, intermittent fever, and in some cases, lung, spleen, and liver involvement. 

Complications of JRA might include problems that are associated with joint growth and eye inflammation like uveitis. The disease can cause the affected joints to either grow too slowly or too quickly, which can cause one leg or arm to be longer or shorter than the other. It can also cause the joint itself to grow unevenly. JRA can also impact overall growth. 

Laboratory Tests 

Although many children who have Juvenile Rheumatoid Arthritis do not show any abnormal findings, the following tests are used to help diagnose JRA or to distinguish it from other forms of arthritis:  

Antinuclear antibody (or ANA) – for detecting the presence of antibodies. It is the most common test to show positive in JRA afflicted children. Around 80% of children who have eye involvement test ANA positive. 

Rheumatoid factor (or RF) – can be negative or positive depending on the kind of JRA that a child has; found more commonly in adults who have rheumatoid arthritis.  

Complete blood count (or CBC) – this test is used for evaluating a child’s hemoglobin as well as white and red blood cells to help with evaluating and monitoring the complications as well as the conditions, like reduced white blood cell count and/or anemia.  

Comprehensive metabolic panel (or CMP) – this test is used to help with evaluating and monitoring a child’s liver and kidney function. 

C-reactive protein (or CRP) or Erythrocyte sedimentation rate (or ESR) – for detecting inflammation within the body. 

Other lab tests might be conducted in order to rule other conditions out that have similar symptoms, including the following:  

HLA-B27 – this genetic test helps with distinguishing the kind of arthritis that a child is affected by. For example, ankylosing spondylitis, or the kind of arthritis that affects the spine.  

Synovial fluid analysis – this test is ordered sometimes in order to detect crystals that might be inside the joint and to check for joint infection signs.  

Blood culture – for ruling out infection 

Other lab tests, as appropriate, like a Lyme disease test