Lumbar puncture (spinal tap)
The spinal fluid samples are sent to a laboratory for analysis. Lab technicians check for a number of things when examining spinal fluid, including:
- General appearance. Spinal fluid is normally clear and colorless. If it's cloudy, yellow or pink in color, it might indicate abnormal bleeding. Spinal fluid that is green might indicate an infection or the presence of bilirubin.
- Protein (total protein and the presence of certain proteins). Elevated levels of total protein — greater than 45 milligrams per deciliter (mg/dL) — may indicate an infection or another inflammatory condition. Specific lab values may vary from medical facility to medical facility.
- White blood cells. Spinal fluid normally contains up to 5 white blood cells (mononuclear leukocytes) per microliter. Increased numbers may indicate an infection. Specific lab values may vary from medical facility to medical facility.
- Sugar (glucose). A low glucose level in spinal fluid may indicate infection or another condition.
- Microorganisms. The presence of bacteria, viruses, fungi or other microorganisms can indicate an infection.
- Cancer cells. The presence of abnormal cells in spinal fluid — such as tumor or immature blood cells — can indicate certain types of cancer.
Lab results are combined with information obtained during the test, such as spinal fluid pressure, to help establish a possible diagnosis.
Your health care professional generally gives you the results within a few days, but it could take longer. Ask when you can expect to receive the results of your test.
Write down questions that you want to ask your doctor or nurse. Don't hesitate to ask other questions that may come up during your visit. Questions you may want to ask include:
- Based on the results, what are my next steps?
- What kind of follow-up, if any, should I expect?
- Are there any factors that might have affected the results of this test and, therefore, may have altered the results?
- Will I need to repeat the test at some point?