RF and Mono Lab

What makes agglutination visible?

Antibodies bind antigenic targets on particles and cross-link them into a lattice

What can particulate indicators be?

Latex beads or red blood cells

What does agglutination and no agglutination look like?

Visible clumps = agglutination

Uniform suspension = no agglutination

What is the rheumatoid factor?

An autoantibody (USUALLY IgM) that binds with the Fc portion of IgG

How does the RF test work?

The kit uses latex particles coated with human gamma globulins (IgG)

RF in patient serum cross-links the coated latex particles (which causes visible agglutination)

Is RF associated with rheumatoid arthritis?

Yes BUT it is not disease specific

What kind of assay is RF?

A passive (indirect) latex agglutination assay: antigen coated particles detect patient antibody

What are the five steps of the RF latex test?

1. Bring serum and reagents to room temperature. Check to ensure specimen integrity (hemolysis and lipemia can interfere)

2. Place 40 microliters of undiluted serum on a slide circle. (DO NOT ADD MORE OR LESS)

3. Add 1 drop of well-mixed RF latex reagent

4. Mix across the circle; rotate gently for 2 minutes

5. Read immeadiately for visible agglutination

RF results: Qualitative means what kind of results?

Agglutination = reactive RF screen

No agglutination = non reactive

RF results: Semiquantitative means to do what?

Make serial twofold dilutions (1:2, 1:4, 1:8)

The last reactive dilution is the endpoint

Epstein-Barr virus (EBV) causes what?

Infectious mononucleosis

What does the Infectious mononucleosis detect?

Heterophile antibodies associated with IM

Not EBV antigen and not EBV-specific antibodies

These antibodies react with antigens on cells from other species

What type of antigen absorbs many non-IM heterophile antibodies?

Guinea pig kidney

What will remaining IM-associated heterophile antibodies agglutinate what?

Preserved horse erythrocytes

How does Remel Color Slide II: qualitative workflow work?

1. Allow reagents and serum/plasma to reach room temperature

2. Place 1 drop of guinea pig kidney antigen (A) at left

3. Place 1 drop of horse erythrocytes (B) at right

4. Add 1 drop of sample/control to A; mix 10 - 15 strokes (mix well to avoid false-negatives later)

5. Blend into B; rock gently for 1 minute

6. Read results immeadiately

What does a positive and negative IM result look like?

Positive = Dark clumps distributed across a blue-green background

Negative = no agglutination; fine granularity on brown/tan background

What other individuals can have a positive RF test result?

Healthy ELDERLY people

SLE (System Lupus Erythematosus) patients

Hepatitis

Syphilis

What can cause a negative results for IM?

Early illness, young age, or inability to produce heterophile antibodies