Final answer:
A drug screen requires special "chain of custody" documentation to ensure that the sample is accounted for at all times and to reduce the risk of tampering.
Step-by-step explanation:
The test that may require special "chain of custody" documentation when collected is c. Drug screen. This is because drug screening is often used in legal contexts where the results might be presented in court or used for employment decisions. A chain of custody ensures that the sample is properly handled and accounted for at all times, reducing the risk of tampering or false results. Tests like a blood culture, crossmatch, and DM (diabetes mellitus) test typically do not require such rigorous documentation unless they are part of a legal investigation or employment-related health assessment.