Final answer:
The maximum interval during which a recipient sample may be used for compatibility testing if the patient has recently been transfused or was pregnant within the past 3 months can be determined through an antibody screen test.
Step-by-step explanation:
When a patient has recently been transfused or was pregnant within the past 3 months, an important consideration for compatibility testing is the presence of antibodies against antigens outside the ABO or Rh systems. To determine if such antibodies are present, an antibody screen test is used. This test involves checking the patient's serum against commercially prepared, pooled, type O red blood cells that express these antigens. If agglutination occurs, further testing is conducted to identify the specific antigen that the patient is responding to.