Which statement about the P blood group antigen is true?

Which statement about the P blood group antigen is true?

• A. It is always stable during storage
• B. It is not present in all individuals
• C. It is not recognized by standard typing
• D. It degrades on storage

Answer: (D)

P antigens on red blood cells can be unstable and may degrade during storage. As red cells sit in storage, membrane components and lipid glycolipids can change or diminish, leading to loss of detectable P antigen over time. Because of this, a unit that originally expressed the P antigen may test weaker or negative after prolonged storage, making storage-related degradation a true statement. In contrast, most individuals do express P antigen (though rare variants exist), so saying it’s not present in all individuals isn’t generally correct. Standard typing can involve reagents that detect P-related antigens when specifically tested, so it isn’t accurate to say it isn’t recognized by standard typing. And while storage conditions can affect many antigens, the key point here is the known tendency of the P antigen to degrade with storage.

P antigens on red blood cells can be unstable and may degrade during storage. As red cells sit in storage, membrane components and lipid glycolipids can change or diminish, leading to loss of detectable P antigen over time. Because of this, a unit that originally expressed the P antigen may test weaker or negative after prolonged storage, making storage-related degradation a true statement.

In contrast, most individuals do express P antigen (though rare variants exist), so saying it’s not present in all individuals isn’t generally correct. Standard typing can involve reagents that detect P-related antigens when specifically tested, so it isn’t accurate to say it isn’t recognized by standard typing. And while storage conditions can affect many antigens, the key point here is the known tendency of the P antigen to degrade with storage.