In lumbar puncture specimen handling, which tube is typically sent to the lab for analysis?

• A. Third tube
• B. First tube
• C. Second tube
• D. Fourth tube

Answer: (A)

The important idea is preserving the CSF sample so the most diagnostic tests—cytology with Gram stain and culture—can be performed accurately and promptly. The first tube collected from a lumbar puncture is designated for these microbiology and cellular analyses because it provides a fresh, least-delayed sample with the most reliable cellular content for staining and culture. The remaining tubes are reserved for chemistry tests (like protein and glucose) or other analyses that require more volume or different handling. In this way, sending the first tube to the lab for routine analysis gives the best chance to detect infection or inflammatory changes early and clearly.