Final answer:
The bilirubin specimen must be protected from light to prevent degradation and ensure accurate test results. Blood samples are centrifuged to obtain plasma. In critical circumstances, type O negative blood is transfused since it's universally compatible.
Step-by-step explanation:
If blood specimens are to be protected from light during transportation to the laboratory for testing, the specimen that requires this precaution is Bilirubin. Bilirubin is a breakdown product of heme from red blood cells and is light-sensitive; exposure to light can lead to the degradation of bilirubin in the sample, which could result in inaccurate test results. Therefore, it is essential to protect bilirubin specimens from light to ensure the reliability of the test.
When collecting blood samples, the specimen is processed to obtain plasma by using anticoagulants such as lithium heparin and then centrifuged. If the patient has a condition like hemolytic anemia with antibodies attached to red blood cells, special consideration during the sample processing might be necessary.
Cross-matching for blood transfusions is a critical step to avoid transfusion reactions. However, in emergency situations, such as severe bleeding following a traumatic accident when there is no time to determine blood type, type O negative blood is transfused as it is considered the universal donor blood type and has the least likelihood of causing a reaction.