A home care phlebotomist had a requisition to collect a complete blood count (CBC), plasma K, partial thromboplastin time (PTT), and prothrombin time (PT). He collected the tubes from the client, who was lying on the sofa with her arm elevated above her shoulder on a table next to the sofa. As he collected the tests in the following order-CBC, K, and finally the PT and PTT- he was careful to invert the tubes as required. Later that day, the lab called the phlebotomist to say that three of the tests would have to be redrawn. Which of these tests most likely had questionable results and needed to be redrawn?