Serological diagnosis in medical microbiology.

Question 1

Most senstive serological tests in order

Answer 1

1. Bacterial neuralization
2. ELISA
3. Immunofluorescence
4. Hemaggultination inhibition test
5. Passive Hemaggultination
6. Complemement fixation test
7. Bacterial agglutination
8. Ring precipitation
9. Gel-diffusion

Question 2

Agglutination (insoluble)

Answer 2

Is the visible clumping of particulate (insoluble) Ag with its specific Ab forming visible lattice.

The Ab is the divalent agglutinating one either IgG or IgM type.
• The reaction can be either on slide or tube agglutination.

• It can be direct or via the use of carrier (Passive or indirect) e.g. Latex, RBCs (hemagglutination), or Staph protein A (Coagglutination). Indirect more easily visible.

• The reaction can be qualitatively or quantitatively expressed.

Question 3

Prozone phenomenon is caused by the blocking effect of what?

Answer 3

IgA

Question 4

Precipitation (soluble) detects what?

Answer 4

pneumococcal capsule

Question 5

Antigens in floctuation tests

Answer 5

cardiolipin
heterophile

Question 6

Postive test for CFT

Answer 6

No hemolysis

Question 7

Difference between RIA and ELISA

Answer 7

ELISA: uses enzymes as Ab or Ah conjugates - safer

RIA: uses radioisotopes as Ab or Ag conjugates (usually Iodine-125, a gamma emitting isotope) - less safe

Question 8

IFA - Immunofluoresence Assay
It’s advantage?

Answer 8

Ag-Ab reaction where the Ab is labelled with fluorescent dye, either Fluorescin or Rhodamine

It’s advantage is it can detect Ags in tissues

Question 8

Most common example for IFA

Answer 8

TP-IFA Treponema Pallidum Immunofluorescent Antibody Test

Question 9

ICT Immunochromatography

Answer 9

Immunochromatographic assays, termed also (Rapid Test), (Point-of-care test, POCT) or (lateral-flow dipstick) immunoassays.

• Based upon Sandwich ELISA assay and run on chromatographic papers or Nitrocellulose membrane by the capillary action.

• The test strips or cartridge contains two type of fixed monoclonal antibodies one at the test (T) zone which is specific to the Ag or Ab of interest (to be tested for), and the other Ab at the control (C) zone which is anti-antibody to the human IgG for validation of reaction components of the test strip or cartridge.

Question 10

Most common tests used

Answer 10

1. Latex tests
2. Rapid test
3. ELISA
4. Flocculation test
5. TPHA (detects syphilis)
6. WB

Question 11

Rarely used

Answer 11

RIA, IFA, CFT