Juvenile rheumatoid arthritis (JRA) is diagnosed mainly after exclusion of other conditions that may affect the joints in children and adolescents less than 16 years of age.
Steps of diagnosing JRA include:-
Detailed history of the symptoms
Usually the symptoms have to be present for at least six consecutive weeks for a diagnosis of JRA. The joint involvement and the associated symptoms need to be assessed from history. Family history of the condition is also significant as evidence shows a genetic basis for the condition
Examination
On examination joint pain, warmth, stiffness and swelling can be detected. Associated features affecting the eyes, swollen lymph nodes, enlarged liver and spleen etc. may also be detected on examination.
Laboratory tests
On routine blood tests non-specific markers for inflammation including Erythrocyte Sedimentation Rate (ESR) and C Reactive protein may be found to be raised.
Specific tests including Rheumatoid factor and Antineuclear antibody (ANA) may be found to be positive. ANA is found to be positive in 60% to 80% of JRA patients. It is commonly positive in pauciarticular disease.
In these children with pauciarticular disease along with uveitis 65 to 85% may test positive for ANA. Thus ANA positivity in pauciarticular JRA signifies an increased association with chronic anterior uveitis and vigilance is mandated to avoid blindness.
Rheumatoid Factor is positive in only 15 to 20% cases of JRA. It is more frequently seen in children with later onset polyarthritis, and is associated with a more aggressive disease course.
X-ray
On X-ray of the affected joints, there may be evidence of joint erosion, damage and narrowing of the space within the joints. X rays also reveal swelling of the soft tissues, localized disturbances in bone growth, early ossification or termination of growth of the ends of the bones.
Excluding other causes
Diagnosis should exclude joint injuries like sprains, strains, fractures, growing pains, viral and bacterial infections, septic arthritis, osteomyelitis, neuroblastoma, leukemias etc.
Further Reading
Unraveling nuanced roles of JAK inhibitors in inflammation