White Blood Cell Differential Count (Lower Respiratory Tract Specimen) – Manual Method
This test measures the types and proportions of white blood cells in a sample taken from your lower respiratory tract, such as sputum. It helps identify infections, inflammation, or other conditions affecting your lungs.
["This test helps doctors diagnose lung infections, inflammation, or other respiratory conditions by examining your white blood cells in sputum."]
Key facts at a glance
- LOINC
- 98020-1
- Short code
- WBC # Lower resp Manual
- Synonyms
- WBC # Lower resp Manual
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 4.5
- Ref high
- 11
- Critical range
- 2 N/A – 30 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- manual-count
- CPT
- 85004
- SNOMED
- 900000000000003002
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Your doctor may order this test if you have symptoms like persistent cough, difficulty breathing, or unexplained lung issues. It’s particularly useful for detecting infections like pneumonia or chronic conditions like COPD.
How the Test Works
A sample of sputum is collected from your mouth or throat and examined under a microscope. A technician counts and identifies different types of white blood cells (neutrophils, lymphocytes, eosinophils, basophils, and monocytes) to assess their presence and proportions.
Sample Collection and Preparation
You’ll likely cough into a sterile container or rinse your mouth with saline before spitting into a cup. The sample is then processed and sent to the lab for microscopic analysis.
What to Expect Before the Test
No special preparation is needed, but avoid smoking or using cough suppressants for 24 hours before testing, as they may affect results.
Reference range
Adult: 4.5-11.0 x 10^9/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test plays a key role in diagnosing respiratory infections, inflammatory diseases, or conditions like asthma or cystic fibrosis. Abnormal cell counts can indicate bacterial, viral, or fungal infections, allergic reactions, or other lung disorders.
Short name
WBC Differential (Lower Resp Tract)
Frequently asked questions
What does a high or low count of certain white blood cells mean?
How long does it take to get results?
Can I eat or drink before the test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy