Reticulocytes are red blood cells that are still developing. They are also known as immature red blood cells. Reticulocytes are made in the bone marrow and sent into the bloodstream. About two days after they form, they develop into mature red blood cells. These red blood cells move oxygen from your lungs to every cell in your body.

RBP is a sensitive marker of undernutrition and the monitoring of its serum concentration allows the monitoring of nutritional status.

Retinol-binding protein (RBP) is an unglycosylated protein synthesised by the liver. The role of RBP is to transport retinol (vitamin A) from the liver to the target tissues (retina, skin, etc.) in the bloodstream. This protein is then metabolized, filtered and reabsorbed in the kidney.

Reverse T3 is a biologically inactive thyroid hormone; however, it does block the conversion of thyroxine (T4) to triiodothyronine (T3). Higher levels of reverse T3 can decrease the effect of thyroid hormone.

RF, IgA by EIA (RDL) refers to the measurement of rheumatoid factor (RF) of the IgA subclass using an enzyme immunoassay (EIA), typically performed at RDL (Reference Diagnostic Laboratory). RF is an autoantibody directed against the Fc portion of immunoglobulin G (IgG) and is commonly associated with rheumatoid arthritis (RA) and other autoimmune conditions. While IgM-RF is the most commonly tested form, IgA-RF may provide additional diagnostic value, particularly in seronegative RA or cases with extra-articular manifestations. Elevated IgA-RF levels have been linked to more severe joint damage and systemic inflammation, and they may correlate with disease activity in rheumatoid arthritis and other autoimmune disorders. This test is typically used alongside other serological markers like IgM-RF, anti-CCP antibodies, and inflammatory markers to improve diagnostic accuracy and assess disease progression.

RF, IgG by EIA (RDL) refers to the measurement of rheumatoid factor (RF) of the IgG class using enzyme immunoassay (EIA) at RDL (Rheumatology Diagnostic Laboratory). Rheumatoid factor is an autoantibody that targets the Fc region of IgG, and its presence is often associated with autoimmune conditions, particularly rheumatoid arthritis (RA) and other inflammatory diseases. While RF is most commonly measured as IgM, the IgG RF subtype can also contribute to disease mechanisms, including immune complex formation and chronic inflammation. Elevated IgG RF levels may indicate rheumatoid arthritis, Sjögren’s syndrome, or other connective tissue diseases, but can also be found in some infections and chronic inflammatory states. Since RF alone is not diagnostic, it is typically interpreted alongside other markers, such as anti-CCP antibodies, ESR, and CRP, to assess autoimmune disease activity.

RF, IgM by EIA (RDL) is a laboratory test that measures rheumatoid factor (RF) of the IgM class using enzyme immunoassay (EIA) methodology. RF is an autoantibody that targets the Fc region of IgG antibodies and is commonly associated with autoimmune conditions, particularly rheumatoid arthritis (RA). Elevated RF IgM levels can indicate inflammatory or autoimmune diseases, including Sjogren’s syndrome, systemic lupus erythematosus (SLE), and other connective tissue disorders. However, RF can also be detected in some healthy individuals or those with chronic infections, making it important to interpret results alongside clinical symptoms and other diagnostic markers. The RDL designation refers to the reference diagnostic laboratory performing the test, ensuring standardized measurement and reliability.

What Is the Rheumatoid Factor (RF) Test?

The Rheumatoid Factor (RF) test is a blood test commonly used to help diagnose rheumatoid arthritis (RA) and other autoimmune conditions. It measures the level of rheumatoid factor, a specific type of antibody in your blood.

What Is Rheumatoid Factor?

Rheumatoid factor (RF) is an autoantibody—a protein made by the immune system that mistakenly targets the body’s own tissues. High levels of RF are often found in people with rheumatoid arthritis or Sjögren's syndrome, another autoimmune disorder.

However, testing positive for RF doesn't always mean you have RA. Some people—especially older adults—may have elevated RF levels without any underlying disease. Likewise, not everyone with RA will test positive for RF.

Rheumatoid Factor (RF) is an autoantibody often found in individuals with autoimmune diseases, most notably rheumatoid arthritis (RA). It targets the Fc region of immunoglobulin G (IgG), forming immune complexes that contribute to inflammation and tissue damage. Detecting RF is crucial for diagnosing and monitoring autoimmune disorders.

One of the methods for measuring RF is Turbidimetric Rheumatoid Factor Detection (Turb RDL). This technique uses turbidimetry, a method that measures the cloudiness or turbidity in a solution caused by antigen-antibody complexes. When RF is present in the serum sample, it reacts with specific antigens, creating immune complexes. These complexes scatter light, and the degree of scattering is directly proportional to the concentration of RF in the sample. The higher the RF levels, the more turbid the solution becomes.

Rheumatoid Factor (RF) IgA is an IgA-class autoantibody that targets the Fc region of other immunoglobulins, similar to RF IgG and IgM. While RF (IgM) is the most commonly tested marker for rheumatoid arthritis (RA), RF (IgA) may provide additional insights into disease severity, progression, and immune system activity.

Rheumatoid Factor (RF) IgG is an immunoglobulin G (IgG) autoantibody that targets the body’s own tissues, particularly the Fc region of other antibodies. While RF is commonly associated with rheumatoid arthritis (RA), its presence can also indicate other autoimmune conditions or chronic infections.

Rheumatoid Factor IgM (RF-IgM) is an antibody commonly measured to help diagnose rheumatoid arthritis (RA) and other autoimmune disorders. Rheumatoid factor is part of a group of antibodies that target the body's own tissues, often mistaking them for foreign invaders. Specifically, the IgM type of rheumatoid factor is the most commonly tested and can be found in the blood of many individuals with autoimmune diseases.

What does an equivocal result mean?

An "equivocal" result means the test result falls into a borderline or "gray area"—neither clearly positive nor clearly negative. This can happen when the measured levels of the biomarker (in this case, Rheumatoid Factor IgM) are slightly above normal but not high enough to be definitively considered positive.

In practice, an equivocal result suggests that:

1. Further Monitoring May Be Needed: The immune system could be fluctuating, so retesting after a few weeks or months might provide a clearer result.
2. Additional Testing Could Help: Equivocal results often lead doctors to order additional tests to gather more information, such as anti-CCP for rheumatoid arthritis or other autoimmune markers.
3. It May or May Not Indicate Disease: In some cases, an equivocal result could suggest a mild immune response or early-stage disease, but in others, it might simply be a variation with no clinical significance.

Doctors often evaluate equivocal results in the context of other symptoms and tests, using the full clinical picture to guide further diagnosis and treatment.

- Common in soil, plants, bathrooms, and in beverages like milk, juice, and water. 
- May be a commensal (=living in a relationship in which one organism derives food or other benefits from another organism without hurting or helping it). 
- Can cause disease in immunosuppressed patients.

Ri Antibody Screen with Reflex to Titer and Western Blot - Anti-Ri can be detected in patients with the paraneoplastic opsoclonus/myoclonus syndrome. Neoplasms most often associated with Anti-Ri include breast cancer, gynecological cancers, and small cell lung cancer.

Riboflavin, also known as Vitamin B2, is a water-soluble vitamin that plays a crucial role in energy production, cellular function, and metabolism. It is a component of two major coenzymes, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which are key players in the metabolism of carbohydrates, fats, and proteins, facilitating the production of energy (ATP) in the body. Riboflavin is also essential for the regeneration of glutathione, one of the body's main antioxidants, thus playing a significant role in protecting cells from oxidative stress and damage. Additionally, Vitamin B2 is involved in the conversion of other B vitamins, including niacin (B3) and pyridoxine (B6), into their active forms, making it essential for maintaining overall B vitamin metabolism. Its role extends to the development and function of the skin, lining of the digestive tract, blood cells, and many other parts of the body.