Examination of Body Fluids: Evaluating Gross Appearance; Performing Cell Counts

Evaluating gross appearance: CSF Spinal fluid is the only fluid that is normally available in quantities sufficient to sample. Adults have 90-150 mL of cerebrospinal fluid (CSF) and neonates 60-90 mL.¹ The spinal fluid bathes the brain and spinal column providing nutrients to, removing waste products from, and acting as a protective cushion for the central nervous system (CNS). Since this fluid circulates around the brain and spinal column, it is an excellent source of information for the condition of the CNS. CSF is collected by lumbar puncture and, ideally, is placed into three or four sterile tubes labeled 1, 2, 3, and 4 in the order in which it is collected. If multiple tubes are received and multiple tests are ordered, tube #1 should be used for chemistry and immunology testing, tube #2 for microbiology, tube #3 for cell counts and differential, and tube #4 for any other tests.¹

The normal appearance of CSF is colorless and crystal clear, resembling water. A cloudy or turbid fluid indicates increased WBCs or protein. A bloody fluid can indicate a traumatic tap in which a blood vessel is inadvertently punctured in the process of collection or blood can mean an intracranial hemorrhage or pathologic bleed. If multiple tubes are collected, there is clearing of the blood from the first tube to the last tube collected in the case of a traumatic tap but a consistent amount of blood in all tubes in the case of a pathologic bleed. If only one tube…

ABBREVIATIONS: CNS = central nervous system; CSF = cerebrospinal fluid; RBC = red blood cell; WBC = white blood cell.