Understanding Your Lab Results
Lab results can feel overwhelming at first. This guide will help you understand the most common blood tests you'll encounter during your leukemia journey.
The Complete Blood Count (CBC)
The CBC is the most frequently ordered blood test. It measures the three main types of blood cells and provides insight into your bone marrow function.
Red Blood Cells (RBC)
| Hemoglobin (Hgb) | Normal: 12-16 g/dL (women), 14-18 g/dL (men) |
| Hematocrit (Hct) | Normal: 36-44% (women), 41-50% (men) |
| RBC Count | Normal: 4.0-5.5 million/ยตL |
Low values indicate anemia. You may need a transfusion if hemoglobin drops below 7-8 g/dL or you have symptoms.
White Blood Cells (WBC)
| WBC Count | Normal: 4,500-11,000/ยตL |
| Absolute Neutrophil Count (ANC) | Normal: 1,500-8,000/ยตL |
| Lymphocytes | Normal: 1,000-4,800/ยตL |
ANC < 500 = severe neutropenia (high infection risk). ANC < 1000 = moderate neutropenia.
Platelets (PLT)
| Platelet Count | Normal: 150,000-400,000/ยตL |
< 50,000 = increased bleeding risk. < 10,000 = may need platelet transfusion.
The Differential (Diff)
The differential breaks down your white blood cells into subtypes. In leukemia, this helps track the percentage of abnormal cells.
Normal Cells
- โข Neutrophils: 40-70%
- โข Lymphocytes: 20-40%
- โข Monocytes: 2-8%
- โข Eosinophils: 1-4%
- โข Basophils: 0.5-1%
Abnormal Findings
- โข Blasts: Immature cells (normally 0%)
- โข High blast % = active leukemia
- โข Disappearing blasts = response to treatment
Other Important Labs
Comprehensive Metabolic Panel (CMP)
Checks kidney function (creatinine, BUN), liver function (AST, ALT, bilirubin), and electrolytes. Important for monitoring treatment side effects.
LDH (Lactate Dehydrogenase)
Marker of cell turnover. High levels may indicate active disease or rapid cell breakdown (tumor lysis).
Uric Acid
Can rise when leukemia cells break down during treatment. Monitored to prevent tumor lysis syndrome.
Flow Cytometry & MRD Monitoring
Flow cytometry is a specialized test that analyzes the physical and chemical characteristics of cells as they flow in a fluid stream through a laser. It identifies cells by their surface markers (called CDs, like CD34, CD33) and is crucial throughout your treatment:
- Diagnosis: Identifies the exact type of leukemia by looking at the specific "fingerprint" of markers on the abnormal cells.
- MRD Monitoring: Measures Minimal Residual Disease (or Measurable Residual Disease) by detecting tiny numbers of leukemia cells that look different from normal healthy cells, even when they are too few to see under a microscope (e.g., 1 in 10,000 cells).
- Relapse Detection: Catches the return of leukemia early by spotting cells with the original abnormal marker fingerprint.
Cytogenetics & FISH
These tests look directly at the chromosomes inside your leukemia cells to identify large structural changes, such as missing, extra, or rearranged chromosomes (translocations).
- Karyotyping (Cytogenetics): A broad look at all your chromosomes. It takes longer (usually 1-2 weeks) because cells must be grown in the lab.
- FISH (Fluorescence In Situ Hybridization): Uses fluorescent probes that "glow" to detect specific, known chromosomal abnormalities quickly (often within a few days).
Molecular Testing (NGS & PCR)
Molecular tests look deeper at the DNA or RNA level to find specific genetic mutations (like FLT3, NPM1, or BCR-ABL) that cannot be seen by looking at chromosomes.
NGS (Next-Generation Sequencing)
A broad screening test that can read millions of DNA fragments simultaneously to identify many possible mutations at once. Usually takes 1-3 weeks. Essential for determining risk and selecting targeted therapies.
PCR (Polymerase Chain Reaction)
A highly sensitive test used to find extremely small amounts of specific, known mutations (like BCR-ABL). Often used to track MRD and verify that a targeted therapy is working.
Post-Transplant Chimerism Testing
If you have had an allogeneic stem cell transplant (cells from a donor), you will undergo regular Chimerism tests. In mythology, a chimera is an animal made of parts from different animals. In transplant medicine, it refers to having two different sets of DNA in your blood: yours and your donor's.
Chimerism tests (usually done using STR-PCR or NGS) track the percentage of your blood and marrow cells that belong to your donor versus the percentage that still belong to you.
100% Full Donor Chimerism
This is the ultimate goal! It means all of your blood and bone marrow cells are originating from the donor's stem cells, indicating the transplant has successfully engrafted.
Mixed Chimerism
This means a percentage of your original host cells remain. Depending on the disease and conditioning intensity, a temporary mixed state can be normal, but increasing host cells could signal an impending relapse or graft failure, prompting your doctor to intervene (e.g., stopping immunosuppressants or giving a Donor Lymphocyte Infusion - DLI).
๐ก Tip: Keep a Lab Tracker
Create a simple spreadsheet to track your key values (ANC, Hgb, Platelets, Chimerism percentages) over time. This helps you see trends and understand how your body responds to treatment.
๐ Learn More
The Leukemia & Lymphoma Society has detailed guides on understanding blood test results.
Lab and Imaging Tests at LLS