Human Physiology — UPSC Mains Model Answer

Red blood cells carry surface antigens (A, B, or both) that trigger immune responses in incompatible recipients. Group O individuals lack both A and B antigens, eliminating the primary trigger for transfusion reactions. The additional absence of the Rh (D) antigen in O-negative blood removes a second major incompatibility risk.

In mass casualty events, road accidents, or surgical emergencies where cross-matching is not feasible, O-negative blood is administered without prior testing. This makes it indispensable in trauma bays, military field hospitals, and disaster relief operations. Its availability directly determines survival outcomes in time-critical situations.

O-negative blood constitutes roughly 7–8% of the global population, creating a structural supply-demand imbalance. National blood transfusion services must maintain strategic reserves of O-negative units while managing rapid depletion during emergencies. Targeted donor recruitment campaigns focusing on O-negative individuals are a recognised policy priority.

Effective blood bank management requires tiered inventory protocols — reserving O-negative stocks for genuine emergencies while using type-specific blood for routine transfusions. Rational utilisation policies prevent unnecessary depletion of this scarce resource, balancing individual patient needs against population-level preparedness.