The method of gathering and analyzing fluid samples depends on the type of test ordered by your doctor. If a blood sample is needed, a trained clinician uses a needle to draw the sample. Getting a sample of cells to check for infection may involve a throat culture. A cotton swab is wiped across the back of the throat, and the specimen is incubated in the lab. The patient supplies a sample of stool or urine using a sanitary container. Lab professionals take extra care to document information about the patient, the doctor, and the nature of the test. The samples are analyzed in the lab, and a report is written. Doctors compare your lab results to a “reference range,” which is a range of scores recorded from testing a large number of people like you-people of the same sex and age.