Once it is determined with reasonable probability that the observed reactivity is due to an "HTLA" antibody, the next decision that needs to be made is how to determine if the patient has a clinically significant antibody or not.
The steps will vary from case to case, depending on how many reactive cells are present on the initial panel. First, you will rule out using the traditional method of using the nonreactive cells without any advanced techniques. If there are close to 50% reactive and non-reactive cells, the most efficient method to rule out would be to run additional cells expressing antigens that have not been ruled out previously until rule outs are complete. If available, using expired panel cells, older donor cells with known phenotypes, or cord blood with known phenotypes are especially useful.
If the initial panel is panreactive or nearly panreactive, and using alternative sources of red cells did not aid in antibody identification, then altering the red cells is likely the next best course of action. The most common ways this can be accomplished is by treating cells with proteolytic enzymes such as papain or ficin, or treating cells with a sulfhydryl reagent such as DTT or AET.
There are additional ways to alter red cells if enzymes or sulfhydryl reagents are unhelpful in resolving reactivity, such as treating with acid, trypsin, alpha-chymotrypsin, pronase, or sialidase, but these are less common and often unnecessary.
Since these treatments alter the red cells in different ways, the antigens that are sensitive or resistant to them differ enough that running one or several treated panels will likely enable you to rule in or rule out the most common clinically significant red cell antibodies, giving you enough information to select red cells safe for transfusion.
Some facilities will test antibody panels using the saline method with no enhancement, as "HTLA" antibodies are typically non-reactive at the saline phase. However, it is recommended to use this technique with caution, and only after common antibodies to red cell antigens have been ruled out with a more sensitive technique since the patient's last transfusion, as this technique is less sensitive and could miss a clinically significant antibody that is low in titer.
