Final answer:
The procedure of withdrawing fluid by suction with a needle is known as a lumbar puncture, a medical test primarily conducted to collect cerebrospinal fluid for diagnostic purposes.
Step-by-step explanation:
The test or procedure described is known as a lumbar puncture, which is used to collect cerebrospinal fluid (CSF) for testing. During a lumbar puncture, a needle is carefully inserted into the lumbar region between two vertebrae to withdraw fluid. This procedure is performed in the lower lumbar area because it is a relatively safe location to insert a needle, due to the anatomy of the central nervous system (CNS).
Performing a lumbar puncture requires strict aseptic techniques to avoid introducing infections. This includes verifying that all the necessary equipment such as the needle, sponge, and instruments are complete and in proper condition, ensuring the fluid sample is correctly labeled with the patient's name, and promptly analyzing the CSF specimens in the clinical chemistry, hematology, and microbiology departments to diagnose conditions such as infections.