What is the primary usage of the first tube of cerebrospinal fluid (CSF) collected?

The primary usage of the first tube of cerebrospinal fluid (CSF) collected is indeed for chemistry studies. This tube is typically used for tests that involve biochemical analysis, such as measuring glucose, protein levels, and evaluating other chemical constituents that can indicate various conditions, including infections or inflammatory processes affecting the central nervous system.

In the context of CSF collection, the first tube is often reserved specifically for this purpose because it minimizes the risk of contamination that could arise from later collected tubes, which may be used for microbiology or other studies. By analyzing the biochemical composition of the fluid in this first tube, healthcare professionals can gain important insights into the patient's health status and potentially identify the presence of diseases such as meningitis or multiple sclerosis.

The other options, while relevant to CSF analysis, are typically designated for subsequent tubes collected during the procedure. For example, microbiology studies would usually use a later tube to minimize contamination from skin flora that could skew results, and hematology studies would also be conducted on subsequent tubes to ensure accurate blood-related measurements in the fluid.