What is a likely cause of sample contamination during blood collection?

The most likely cause of sample contamination during blood collection is using unsterile equipment or not sanitizing the skin properly. Proper sanitation is critical in phlebotomy to prevent any introduction of pathogens or foreign substances into the blood sample. When the skin is not adequately cleaned, bacteria and other contaminants can be transferred from the skin surface into the sample, compromising its integrity and potentially leading to erroneous test results.

Inserting multiple needles can increase the risk of complications and discomfort for the patient, but it is not a direct cause of contamination to the collected samples. Transferring samples too quickly may affect the handling of the samples but wouldn't inherently cause contamination. Using the wrong collection tubes affects the quality of tests performed on the samples but does not lead to contamination per se. Thus, the emphasis on proper sanitation and equipment sterility is crucial in preventing contamination during blood collection procedures.