Antibody titration is a semiquantitative measure of antibody strength. Comparison of results over time can be used to assess disease activity. It is used during pregnancy to determine severity of maternal alloimmunization in hemolytic disease of the newborn.
Testing:
• sequential dilutions of antibody containing fluid is tested against an antigen system
• in the blood bank, the typical antigen system are red blood cells
• the agglutination of the red cells are graded with the a score given for the strength of the agglutination reaction seen
Tube Dilutions for Testing
|
1:1 |
1:2 |
1:4 |
1:8 |
1:16 |
1:32 |
1:64 |
1:128 |
1:256 |
1:512 |
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Grading Agglutination Reactions
|
Gross Agglutinates |
Free Red Cells |
Microscopic agglutinates |
Reaction Strength |
Score Value |
|
single clump |
none |
|
4+ |
12 |
|
few very large clumps |
none |
|
3+s, 4+w |
11 |
|
several large clumps |
none |
|
3+ |
10 |
|
medium clumps |
none |
|
2+s, 3+w |
9 |
|
medium & small |
none |
|
2+ |
8 |
|
medium & small |
none |
|
2+w |
7 |
|
medium & small |
present |
|
1+s |
6 |
|
small |
present |
|
1+ |
5 |
|
very small |
present |
|
1+w |
4 |
|
weak granularity |
present |
many |
+/-macro |
3 |
|
none |
present |
few |
+micro |
2 |
|
none |
present |
rare |
rough |
1 |
|
none |
even suspension |
none |
0 |
0 |
Endpoints:
(1) for prenatal testing and reagent evaluation, the highest dilution giving a reaction >= 1+
(2) for titration endpoint, the lowest dilution giving a reaction = 0
(3) endpoints are reported as the reciprocal of the dilution (dilution of "1:X" reported as "X")
titration score =
= SUM (agglutination scores for all dilutions)
Interpretation:
• A significant titer change = 3 or more tube dilution difference.
• A significant titration score change = 10 or more points
Specialty: Clinical Laboratory
