Features of reactions caused by the HTLA:
(1) The reactions are observed primarily in the antiglobulin phase.
(2) The reactions show weak and variable agglutination.
(3) The reactions may not be reproducible.
(4) Agglutination strength persists in high levels of serial dilution (1:16 or higher, up to 1:2048 or more).
(5) The agglutination reactions do not match those expected for common antibodies and usually associated with high frequency antigens.
Antigens associated with HTLA:
(1) Chido and Rodgers
(2) Cost and York
(3) Knops-Helgeson and McCoy
(4) John Milton Hagen
(5) Holley and Gregory
(6) Bga
Differential diagnosis:
(1) weak antibody (tends to disappear with dilution, usually by 1:8)
Of the antigens that are considered HTLA, not all instances will show the persistence with dilution. On the other hand, antibodies to other antigens can show a similar behavior. However, recognizing the behavior can help to direct a workup that otherwise can be difficult.
Once an HTLA is recognized as such then otherwise compatible blood can be released for transfusion. It is usually not necessary to match for this set of antigens.
