RANDOM C3, BAT, STREP, AUTOIMMUNE, CRP, IM Flashcards
What is agglutination?
A serologic reaction where particulate antigens form clumps in response to antibodies.
What is the difference between direct and indirect agglutination?
Direct uses a known antiserum to identify unknown antigens, while indirect detects antibodies using known antigens.
What is complement fixation used for?
Detecting antigen-specific antibodies.
What are the two components of complement fixation?
The first is the patient’s serum exposed to a known antigen and complement; the second is the indicator system using sheep RBCs and anti-sheep antibodies.
What indicates a positive complement fixation test?
The absence of red cell lysis, meaning all complement was fixed by antigen-antibody complexes.
What indicates a negative complement fixation test?
The presence of hemolysis, meaning complement was not fixed.
What is the principle of passive agglutination?
Known antigens are coated onto inert particles like latex beads to detect specific antibodies.
What is reverse passive agglutination?
The antibody is attached to carrier particles instead of the antigen.
What is agglutination inhibition?
A highly sensitive reaction used for detecting small amounts of antigens.
What are common clinical applications of agglutination tests?
Diagnosis of infections such as typhoid fever, syphilis, and streptococcal diseases.
What bacterial infections are commonly diagnosed using febrile agglutination tests?
Typhoid fever, typhus fever, brucellosis, and tularemia.
What principle does the Widal test use?
Direct agglutination of Salmonella ‘O’ and ‘H’ antigens with patient serum.
What specimen is used for the Widal test?
Blood, urine, and stool samples.
What are the interpretations of the Widal test based on agglutination levels?
1+ (25% agglutination), 2+ (50%), 3+ (75%), 4+ (100%).
What is the Weil-Felix test used for?
Diagnosis of rickettsial infections using Proteus OX antigen cross-reactivity.
What diseases are diagnosed with the Weil-Felix test?
Epidemic typhus, scrub typhus, Rocky Mountain spotted fever.
What is the Brucella agglutination test used for?
Diagnosis of brucellosis, a zoonotic infection.
What specimen is used for the Brucella test?
Serum.
What serologic tests are used for diagnosing syphilis?
VDRL, RPR, TPHA, and FTA-ABS.
What antigen does the VDRL test use?
Cardiolipin-cholesterol-lecithin suspension.
What is the principle of the VDRL test?
Microscopic flocculation.
What indicates a positive VDRL test?
The presence of floccules under low power magnification.
What is the RPR test?
A rapid plasma reagin test using carbon-coated cardiolipin antigen.
What is the principle of the RPR test?
Macroscopic flocculation.
What is the TPHA test used for?
Treponema pallidum hemagglutination test for detecting syphilis antibodies.
What specimen is used for the TPHA test?
Unheated serum samples.
What is the principle of the TPHA test?
Indirect hemagglutination.
What test is used for confirming syphilis diagnosis?
Fluorescent treponemal antibody-absorption (FTA-ABS) test.
What are serologic tests used for diagnosing streptococcal diseases?
ASO, Streptozyme, and DNase B tests.
What is the ASO titer test used for?
Detecting anti-streptolysin O antibodies.
What is the principle of the ASO test?
Neutralization reaction.
What does a high ASO titer indicate?
A recent streptococcal infection.
What is the normal ASO titer range?
0-125 IU/mL.
What is the principle of the ASO latex slide test?
Passive agglutination.
What is the Streptozyme test used for?
Screening for multiple streptococcal antibodies.
What is the principle of the Streptozyme test?
Passive hemagglutination.
What is rheumatoid factor (RF)?
An autoantibody against the Fc portion of IgG.
What is the RF test used for?
Diagnosing rheumatoid arthritis.
What is the principle of the RF latex slide test?
Latex agglutination.
What is C-reactive protein (CRP)?
An acute-phase reactant associated with inflammation.
What is the principle of the CRP slide test?
Latex agglutination.
What is infectious mononucleosis (IM)?
A self-limiting disease caused by Epstein-Barr virus.
What test is used for IM diagnosis?
Paul-Bunnell test or rapid slide test.
What is the principle of the Paul-Bunnell test?
Heterophile antibody agglutination using sheep RBCs.
What is the heterophile antibody titer cutoff for IM diagnosis?
1:56 or higher.
What is the Davidsohn differential test used for?
Differentiating heterophile antibodies in IM from other conditions.
What are the characteristic cells in IM blood smear?
Downey cells (atypical lymphocytes).
What is the sensitivity of heterophile antibody tests in IM?
90-95% after the first week of infection.
