What is the RA latex turbid test?

The rheumatoid arthritis (RA) latex turbid test is a laboratory test that’s used to help your doctor diagnose RA and other autoimmune diseases.

RA is a chronic disease that leads to inflammation of your joints. In some cases, the inflammation may be so severe that it affects how your joints function. It can also cause joint deformities.

RA is an autoimmune disease. An autoimmune disease is when your immune system attacks a healthy part of your body by mistake.

People with RA produce a specific type of antibody, known as rheumatoid factor (RF). It can be found in the blood or joint fluid of most people with RA. Another antibody, CCPAb, often appears before the RF. There is a subset of RA that is seronegative, or without RF or CCPAb.

The RA latex turbid test uses an RF-specific antibody that is affixed to a latex bead to check for the presence of RF in a serum (blood) sample. When the RF-specific antibodies on the beads encounter RF, they bind tightly to the RF. This binding causes a decrease in the light intensity that can be transmitted through the particles in the sample (turbidity). An increase in the turbidity of the sample indicates the presence of RF.

Why is this test done?

Your doctor may order an RA latex turbid test if you’ve reported symptoms of RA. These symptoms include joint pain or swelling, or unexplained symptoms like rashes, muscle pain, and fevers.

In addition to the RA latex turbid test, your doctor may also order additional tests that can help check for autoimmune conditions. Examples of some of these tests include:

How is the test done?

In order to conduct this test, your doctor will need to collect a blood sample from a vein in your arm. The sample is then typically sent out to a laboratory where the test is performed.

What’s considered “normal”?

The expected normal value for the RA latex turbid test is less than 14 international units per milliliter (IU/mL).

Values higher than this could be an indication of the presence of RA or other autoimmune disorders, post-viral syndromes, and underlying cancers. The higher your result value is, the stronger the likelihood that you have RA. However, some people may have a high value without having RA, and some people with RA may not have a high value. The CCPAb titer is considered a better test for RA.

If you have only a slightly higher-than-normal RA latex turbid value, your doctor will very likely order additional tests to confirm a diagnosis.

What causes high results?

Generally speaking, a higher-than-normal RA latex turbid test result is indicative of RA.

However, you can still have a higher-than-normal test result and not have RA. There are a number of other diseases or conditions that can cause a high result value. These include:

Additionally, a higher-than-normal test result can also be found in older adults and in a low percentage of healthy people.

In order to help confirm a diagnosis of RA following a high RA turbid latex test result, your doctor may order additional tests. The tests may include:

  • Cyclic citrullinated peptide (CCP) antibody test. Similar to the RA latex turbid test, this test also assesses the presence of another specific type of antibody commonly found in people with RA. This antibody appears early in the disease.
  • Erythrocyte sedimentation rate (ESR) test. This test measures how fast your red blood cells settle at the bottom of a glass tube after an hour. The faster the red blood cells settle, the larger the amount of inflammation present.
  • C-reactive protein (CRP) test. This blood test measures a substance that is produced by your liver. High levels indicate a high level of inflammation. This test is thought to be a more sensitive indicator of inflammation than the ESR test.
  • Musculoskeletal ultrasound. This imaging test can detect inflammation.
  • X-rays. Your doctor may also use X-ray images to check for inflammation in your joints. X-rays can show osteopenia, an early sign of inflammation. The hallmark X-ray change for RA is erosion.

When to see a doctor

You should contact your doctor if you’re experiencing symptoms of RA. Some general symptoms of RA include:

  • pain or swelling of your joints that persists
  • stiffness of your joints, particularly in the morning
  • impaired joint movement or pain that worsens with joint movement
  • bumps, also referred to as nodules, over your joints

Additionally, you should contact your doctor if you’re experiencing symptoms of other conditions that can cause a high RA latex turbid test result, such as lupus or Sjögren’s. These symptoms can include:

  • skin rash
  • stiffness of your joints, particularly in the morning
  • unexplained weight loss
  • fever
  • sores in your mouth or nose
  • fatigue
  • dry or itchy eyes
  • dry mouth that makes it hard to speak or swallow
  • unusual dental decay, especially cavities at the gum line

Your doctor will work with you to discuss your symptoms and will order tests to aid in a diagnosis. Because RA has a strong genetic component, tell your doctor if you have family members with RA or other autoimmune diseases. With a diagnosis, you can move forward together to discuss a treatment plan.