White Blood Cell Differential (Other Fluids) – Qualitative

Why This Test Is Done

Doctors may order this test if you have symptoms like fever, persistent pain, swelling, or unusual fluid buildup in areas like the brain, lungs, or joints. It can also be part of investigations for unexplained infections, autoimmune diseases, or conditions causing abnormal fluid accumulation.

What to Expect Before the Test

No special preparation is typically needed. If fluid is collected from a specific site (like CSF), you may experience mild discomfort during the procedure. Follow any instructions your doctor gives for avoiding medications or foods that could affect results.

How the Test Is Performed

A healthcare provider collects fluid (e.g., from a spinal tap, joint aspiration, or other drainage) and sends it to the lab. Microscopic examination identifies and counts different types of white blood cells (neutrophils, lymphocytes, eosinophils, basophils, monocytes) based on their appearance.

Possible Results and Interpretation

Results are qualitative (descriptive rather than numeric) and compare the proportions of WBC types to typical patterns. For example, high numbers of neutrophils may suggest infection, while high lymphocytes could indicate a viral infection or autoimmune response. Your doctor will interpret results in the context of your symptoms and medical history.