A researcher conducting a study on the incidence of mutations to the MDR-1 gene in breast cancer has preliminary evidence of a link between mutated MDR-1 and early recurrence. The researcher begins a new trial using prospectively collected tissue samples to further examine the link between the genetic abnormality and disease progression. He believes that he may want to re-contact some or all of the tissue donors (subjects) if the research indicates a positive link between MDR-1 mutation and early disease recurrence. What is the best procedure for an investigator planning to re-contact study subjects who provided tumor tissue for the study?

The best procedure is to send an email, or make a call to the participants.

Explanation:

When a scientific experiment is carried out and this experiment requires human participants, it is essential that each participant provide some information such as phone number and email address. This is because during the research there may be a need to call these participants again, either to repeat a step in the experiment, to get more samples than are being tested in the experiment, or to request additional information, important for the research.

For this reason, we can say that in relation to the question above, the best way for the researcher to get in touch again with the participants of the experiment who provided tumor tissue for the study is through an email or a phone call.