What is the best source of HLA-compatible platelets?

Siblings are considered the best source of HLA-compatible platelets due to the way human leukocyte antigen (HLA) inheritance occurs. Each person receives one set of HLA genes from their mother and one from their father. This means that siblings have a 25% chance of being HLA-identical and a 50% chance of being HLA-haploidentical. HLA compatibility is crucial in transfusions, especially for platelet transfusions, as it reduces the likelihood of immune reactions such as platelet refractoriness.

The closer the genetic relationship, like that between siblings, the higher the chance of finding compatible HLA types. This makes siblings the most reliable option for HLA-matched platelet donations. Other family members, such as parents or cousins, have a lower probability of being HLA-compatible compared to siblings, making them less ideal sources for platelet transfusions when HLA matching is necessary.