rheumatoid factor test and principle

overview

RF is an  autoantibody, an IgM (immunoglobulin M) protein that is produced by the body‘s   immune system. Autoantibodies usually attack the patient‘s own tissues, mistakenly identifying   them as ―foreign.‖ While the role of RF is not well understood, it is not thought to directly cause   joint damage but to promote the body's inflammation reaction, which in turn contributes to   autoimmune tissue destruction.

 Not all people with rheumatoid arthritis have detectable rheumatoid factor. Those who do notare said to be "seronegative".

 Why It Is Done

 The rheumatoid factor (RF) test is primarily used to help diagnose  rheumatoid arthritis (RA) andto distinguish it from other forms of arthritis and other conditi ons that cause similar symptoms ofjoint pain, inflammation, and stiffness as gout.

Sample

Only serum sample

Note:

• The specimens may be stored at 2-8ºC for 48 hours. For longer periods of time
  freeze serum at or below –20ºC
• Do not use haemolysed, lipaemic , contaminated serum specimens or  high lipimic
  samples which may cause a falsely high rheumatoid factor (RF) result.

Procedure

Principle

The earliest tests, and those still most widely used clinically rely on the agglutinating properties   of the IgM  class of RF. IgG, usually human or rabbit, is bound to a particulate carrier, and the   presence of RF is then detected by agglutination or flocculation of the respective indicator   system. Carrier particles frequently used include latex, and erythrocytes.

Semi-quantitative analysis

to determine the antibody content of a serum involves  serial  dilutions of the serum and
determination of an end point (the last dilution at which agglutination can be visualized). The
reciprocal of this dilution is known as "antibody titer".

latex agglutanation test

Qualitative assay

• Positive: The reagent will agglutinate (clump) in the presence of RF.
• Negative: No agglutination generally indicates absence of RF

Semi-quantitative assay 

The titer is expressed as the highest dilution showing agglutination

Normal levels

Normal levels of RF in adults are < 8 mg/l

Normally about 5% to 10% of people over age 65 have an elevated RF level.

Interpretation 

• In patients with symptoms and clinical signs of  rheumatoid arthritis, the presence of
  significant concentrations of RF indicates that it is likely that they have RA.
• High concentrations of RF are often found in people with active cases of rheumatoid arthritis,
  and it correlates with the severity of signs or symptoms  (Prognosis worse with high titer at
  onset). 
• RF Incidence increases with duration of disease
• • Three months: 33% 
  • Six months: 45% 
  • One year: 75% 
  • Eighteen months: 90% 

Note:  A negative RF test does not rule out RA. About 20% of patients with RA will be
persistently negative for RF and/or may have very low levels of RF

Note:  The RF test is sensitive but nonspecific. It is most closely associated with
rheumatoid arthritis (RA) but may also be present in a variety of other conditions such as:

• Autoimmune disease
• • Sjogren's Syndrome (75 to 95%)
  • Systemic Lupus Erythematosus (15 to 35%)
  • Scleroderma (20 to 30%)
  
  
• Infections
  
  • Osteomyelitis
  • Tuberculosis
  • Syphilis
  • parasitic diseases (e.g., malaria, schistosomiasis, filariasis)
  • Hepatitis (Acute and Chronic) and hepatic cirrhosis (10% to 40%)
  • Leukemia, and multiple myeloma

blood groups types explained and test methodology

blood groups test - blood groups types - blood groups explained

overview

What is a blood group?
Red blood cells contain certain proteins on their surface. These proteins are called antigens.
There are various types of red blood cell antigens  -  the ABO and rhesus types are the most important

ABO antigens

The two major antigens or surface identifierson human RBCs are the A and B antigens.Blood is grouped according to the presence orabsence of these antigens.

ABO antibodies (Isohaemagglutinins)

Anti-A and Anti-B, the common IgM antibodies   to the RBC surface antigens of the  ABO blood   group system, are sometimes described as   being "naturally occurring";  however, this is a   misnomer, because these antibodies are   formed in infancy by sensitization in the same   way as other antibodies.  The theory that explains how these antibodies   are developed states that antigens similar to the A and B antigens occur in nat ure, including in   food, plants, and bacteria. After birth   (during  the first years of life)  an infant's gut becomes   colonized with normal flora that express these A-like and B-like antigens, causing the immune   system to make antibodies to those antigens that the red blood cells do not possess. People   who are blood type A will have Anti-B antibodies, blood type B will have Anti-A antibodies, blood   type O will have both Anti-A and Anti-B antibodies, and blood type AB will have neither. 

These antibodies are of the IgM class, which have the capability of agglutinating (clumping) and   damaging red blood cells within the blood vessels, possibly leading to death.  The ABO system

The ABO system

According to the AB0 blood group system there are four different kinds of blood groups: A, B,
AB or O

• A blood group individuals will have type A antigens on the surface of red blood cells and anti-B antibodies in plasma.  
• B blood group individuals will have type B antigens on the surface of red blood cells and anti-A antibodies in your plasma.
• AB blood group are those who will have type A and type B antigens on the surface of red blood cells and no antibodies to A or B antigens in plasma.
• O blood group are those who will have neither type A or type B antigens on the surface of red blood cells but will have anti-A and anti-B antibodies in plasma.

when to get tested?

When need to be transfused with blood or blood components

Cases in which blood or blood products are needed for treatment may include:

• Severe anemia 
• Surgical patients with intra-operative or post-operative bleeding Injury or trauma patients with excessive blood loss 
• Bleeding disorders such as hemophilia

who can receive blood from whom?

Of course you can always give A blood to persons with blood group A, B blood to a person with blood group B and so on. But in some cases you can receive blood with another type of blood group, or donate blood to a person with another kind of blood group.

Universal blood donor

 A universal blood donor is someone who has an O blood   type and is Rh negative. This means that they have no A or   B antigens or Rh factor on their red blood cells. Their red   blood cells can be given to a patient with any ABO or Rh   blood type

Universal blood recipient

 A universal recipient is a person who has an AB blood type   and is Rh positive. They can receive red blood cells of any   ABO or Rh type with no risk

what happens when blood clumps or agglutinate?

For a blood transfusion to be successful, ABO  and Rh blood groups must be compatible   between the donor blood and the patient blood. If they are not, the red blood cells from the   donated blood will clump or agglutinate. 

The A antigen and the A antibodies can bind to each other in the same way that the B antigens   can bind to the B antibodies. The red blood cells will be linked together, , by the antibodies.

The agglutinated red cells can clog blood vessels and stop the circulation of the blood to various   parts of the body. The agglutinated red blood cells also crack and its contents leak out in the   body. The red blood cells contain hemoglobin which becomes toxic when outside the cell. This   can have fatal consequences for the patient.

sample

Whole blood (EDTA   anticoagulant)

procedures

Reagents for ABO Typing

The monoclonal Anti-A, Anti-B reagents are murine monoclonal   antibodies of IgM  class, secreted by mouse hybridoma cell lines,   which were selected for their ability to agglutinate specifically   human RBCs bearing blood group antigens A and B on direct   agglutination tests (slide, microplate and tube test).

Assay method

• On  a clean  slide, carefully put  two  drops of blood and makesure that the drops do not touch one another.
• Add a drop of anti-A to the first  blood drop ,mix the two drops,using a wooden stick. Check and see if agglutination occurred. 
• Add a drop of anti-B  to  the second  blood  drop ,mix the two drops, using  a  wooden stick.   Check and see if agglutination occurred.

Results