Knowing how you will handle a difficult situation will tell the interviewer if you have the the right attitude for this job. Being a clinical lab technician means you have to deal with people from very different backgrounds and with varying personalities. Give the interviewer an example of how you would handle an angry patient.
"I believe acting calmly and speaking rationally is a great way to calm someone who is angry and I try to be the voice of reason without making someone feel that I am belittling them."
"I think it is important to try and find out what has made the patient mad. If it is something such as not being called as quickly as he had expected, a simple explanation regarding what caused the delay may help calm him."
"There are a couple of different approaches and safety is, of course, the most important thing to consider. If I were to try and provide care to someone who is angry, he could become combative which could result in injury to him, to me, or to both of us. I feel the best approach is to ask what has made the patient upset and try to resolve the underlying cause, if at all possible."