Recently, some of you have been asking me about the accuracy of the home blood typing kits, available on Amazon, etc. According to physicians with whom I have spoken, the tests are highly accurate with common blood types, possibly as high as 99%. However, there have been problems and inaccuracies when rare blood types have been tested in this manner. These tests can determine the A,B,AB, or O status, and also the Rh factor presence or absence.
It used to be that when a child was born, the pediatrician would write the child's blood type on the paperwork that went home with the parents. This is apparently no longer being done, and parents, are therefore curious. Please know that normally when someone needs blood, they are immediately typed and cross matched and their blood is tested for compatibility with the units that the hospital expects to give them. A plasma expander may be given while waiting for this process to be completed, and sometimes a unit of O negative, the universal donor is given while the patient is waiting. Even if you know your blood type, that process does not change. No one is going to take your word for your blood type.
This said, I do understand and sympathize with families who would like to know their family members blood types. In a family I know, the father has the same blood type as the daughters, and the mother has the same blood type as the sons. In an emergency, this might be important information to have, although only very rarely now, does someone donate blood that winds up being administered to a family member.
Please know that if you are seeking to confirm a child's parentage that this is not the way to go. A child doesn't always have the blood type of either of his parents, as he may have a type for which both of his parents have a recessive gene. If DNA testing is what you need, then ask your physician. I don't know how accurate the home tests for that really are.
