WBC (White Blood Count)
Test Overview
The White Blood Cell (WBC) Count is a routine blood test used to measure the number of white blood cells in the blood. White blood cells are crucial components of the immune system, responsible for defending the body against infections, inflammation, and foreign invaders. An abnormal WBC count can indicate an underlying infection, immune system disorder, or other health conditions.
Test Types
- Complete Blood Count (CBC): Includes the WBC count as well as other blood components such as red blood cells (RBCs), hemoglobin, hematocrit, and platelets.
- Differential WBC Count: Breaks down the total WBC count into different types of white blood cells (neutrophils, lymphocytes, monocytes, eosinophils, basophils), providing more detailed information about immune function.
WBC Test Results & Ranges
| Test Component: | Normal Range: | Abnormal (Possible Conditions): |
|---|---|---|
| WBC Count (Total) | 4,500–11,000 cells/µL | Elevated: Infection, inflammation, leukemia; Decreased: Viral infections, bone marrow disorders, autoimmune diseases |
| Neutrophils (Segs) | 40%–60% of WBC count | Elevated: Bacterial infections; Decreased: Bone marrow problems, severe infections |
| Lymphocytes | 20%–40% of WBC count | Elevated: Viral infections, leukemia; Decreased: HIV/AIDS, bone marrow disorders |
| Monocytes | 2%–8% of WBC count | Elevated: Chronic infections, inflammation, leukemia |
| Eosinophils | 1%–4% of WBC count | Elevated: Allergies, parasitic infections, autoimmune disorders |
| Basophils | 0.5%–1% of WBC count | Elevated: Allergic reactions, chronic inflammation, blood disorders |
Expected Turnaround Time
- Results Available: 24 hours or less (for a CBC with WBC count)
Specimen Requirements
- Sample Type: Blood sample (venipuncture)
- Container: EDTA (lavender-top) tube for complete blood count (CBC)
Collection Instructions
- No fasting required, but it’s best to avoid heavy exercise before the test to avoid affecting the results.
- Avoiding infection at the time of the test is important, as an active infection can influence the WBC count.
- Medications: Inform the healthcare provider of any medications you’re taking (e.g., corticosteroids, antibiotics) as they can influence the WBC count.
- Storage: Blood samples should be processed promptly to ensure accurate results.
Test Details
- Clinical Use: A high WBC count (leukocytosis) can indicate infection, inflammation, or bone marrow problems, and can be a sign of leukemia or other cancers. A low WBC count (leukopenia) can suggest viral infections, bone marrow disorders, or an immune system deficiency, such as HIV/AIDS. The differential WBC count helps assess the specific type of white blood cell involved, providing more detailed information on the cause of abnormal levels. Often used in conjunction with other tests to monitor infections, inflammatory diseases, and immune system health.
- Limitations: Medications, stress, or physical exertion can influence WBC counts. Timing of the test relative to the phase of an infection or treatment can affect results. Blood volume may be a concern in certain patients, particularly in infants or those with difficult veins.
The WBC test is a crucial tool in diagnosing infections, monitoring immune system health, and detecting potential blood disorders.