Working for many years in the Middle East/Gulf, I have encountered significant antibodies that can only be detected at enzyme phase. This is especially true of Rh system antibodies, particularly anti-c in an R1R1 patient. I have attached an example.
The reasons I strongly recommend this practice are:
- Weak Rh system antibodies (as above)
- Confirmation of enzyme-labile antibodies, especially if there may be both enzyme-labile and enzyme-resistant antibodies
It is also important to consider which enzyme to use: bromelin, ficin, or papain usually and sometimes trypsin or chymotrypsin. They do not always attack at the same site.
In addition to most common MNSs and Duffy system antibodies, many Kell antibodies (e.g. K or K1, Kpa) are labile with papain but less so or not at all with ficin.
Using enzymes is a double-edged sword since they may enhance cold antibodies and thus cause nonspecific reactions. Thus, I know many of you may not routinely include them in your workups.
It is essential to follow the manufacturer’s recommendations for their use. If you make your own enzyme-treated cells and prolong the incubation, you may get false positivity. You should also be careful about using potentiators with enzyme-treated cells—normally I run them in saline, not LISS!
Since anti-c may cause severe hemolysis and severe hemolytic disease of the newborn, I am especially vigilant in my R1R1 patients, particularly females of child-bearing age and all chronically transfused patients. I prophylactically match R1R1 patients with R1R1 RBCs in these categories, regardless if either anti-E or anti-c are expressed.
I would be very interested to know your practices? When do you use enzymes?