Reactive Arthritis and Lab Testing

Reactive arthritis is generally an autoimmune condition. It gets its name for the fact that it usually occurs as a reaction to an infection somewhere in the body. Apart from being uncommon, it’s a painful type of inflammatory arthritis that targets the lower back, fingers, toes, heels, and joints, such as ankles or in the heels. Additionally, it is linked with inflammation of the eyes, urethra, and sometimes mucous membranes and skin.  

In most cases, two kinds of bacteria cause reactive arthritis, bacteria involved with genital infections and bacteria involved with intestinal infections. The bacterium that brings about chlamydia, Chlamydia trachomatis, is regarded to be a trigger of reactive arthritis. However, it can be triggered by certain intestinal infections, as well as other sexually transmitted diseases. Common intestinal pathogens, such as Yersinia, Salmonella, Shigella, and Campylobacter, are usually the cause of food contamination.  

As aforementioned, reactive arthritis is quite uncommon, and not all people who develop one of these infections will get reactive arthritis. Genetic and gender predisposition are some of the risk factors when it comes to reactive arthritis. In most cases, the disorder is seen in men between 20-50 years, although it can happen at any age. Although it occurs rarely, women can also acquire reactive arthritis.  

Specific individuals are at an increased risk since they are positive for HLA-B27, which is a protein (named HLA or human leukocyte antigen) that is commonly found on cell surfaces. Also, the gene that typically codes for the HLA-B27 is approximated to be available in about 65%-96% of people with reactive arthritis. Still, HLA-B27 is found in only around 6% of the entire U.S. population. While having HLA-B27 is one of the risk factors for reactive arthritis, there is still some likelihood for individuals who are negative to HLA-B27 to get reactive arthritis, and it might be that other genetic factors are considered.  

Signs and Symptoms

For reactive arthritis, the signs and symptoms might include swelling and pain in several joints that occur suddenly 1-4 weeks after the infection. Non-joint inflammation might occur in the eyes as conjunctivitis, the skin, the urinary tract (bladder, urethra prostate gland), reproductive organs, or mouth. Symptoms might disappear spontaneously and won’t recur, or the condition might persist.  

Around one-third of the people who get reactive arthritis will also go through the following: 

  • Conjunctivitis or Uveitis: The inflammation of the thin membrane covering the eyeballs and lines of the inner eye (uveitis) or the eyelids (conjunctiva). Typically, conjunctivitis causes itching and redness, whereas uveitis is more severe and causes light sensitivity, blurring of vision, pain, and redness in the eye.  
  • Urethritis: The inflammation of the tube that joins the bladder to the exterior part of the body (urethra). Usually, this leads to discharge that is visible in the vaginal area or at the tip of the penis. Also, it causes pain or burning during urination. Men might also have inflammation of the prostate gland (called prostatitis), while women might experience inflammation of the cervix (known as cervicitis), even though urethritis is usually absent in women.  
  • Arthritis: Swelling, redness, and pain generally affecting the feet, ankles, and the knees; usually leads to heel pain; often associated with buttock and lower back pain; can cause swollen toes and fingers; can cause spondylitis (inflammation of the joints within the spine’s vertebrae) 
  • Certain skin symptoms can also be associated with reactive arthritis, such as painless penile sessions, rash, ulcers, and bumps on palms of the hands or soles of the feet. 

Laboratory Tests 

There is no single test available to diagnose reactive arthritis. Therefore, a diagnosis is often based on the individual’s signs and symptoms, like swelling or pain in affected joints, and proof of a past or current infection. Furthermore, healthcare practitioners might suggest the following tests to assist in confirming the diagnosis: 

Erythrocyte sedimentation rate (ESR): To examine for inflammation, enhanced with reactive arthritis and other diseases.  

HLA-B27 antigen: To look for a protein that is commonly found on cell surfaces. If found positive for this protein, it means a higher than average risk of acquiring specific autoimmune disorders, such as reactive arthritis. 

C-reactive protein (CRP): To examine for inflammation, enhanced with reactive arthritis and other diseases. 

Additionally, healthcare practitioners might order other tests to figure out the infection that caused the reaction; these include: 

Chlamydia test: To look for proof of the bacterium called Chlamydia trachomatis. In case it’s positive, considering early treatment could lower arthritis progression.  

Synovial Fluid Analysis: To check for an infection in the joint.  

Urinalysis and Urine Culture: To identify a urinary tract infection.  

Stool Culture: To check for Yersinia, E. coli, Campylobacter, and Salmonella 

HIV Test: To find out if someone is HIV-positive. However, it is generally known that reactive arthritis is associated with other infections to which those infected with HIV have been more exposed to instead of HIV infection itself. 

Some tests might be recommended to rule out other reasons for the symptoms: 

Antinuclear antibody (ANA): To assist in ruling out other diseases, like lupus 

Rheumatoid factor (RF): To assist in ruling out other diseases, like rheumatoid arthritis