From the Guidelines
A Complete Blood Count (CBC) with differential is a crucial diagnostic test that provides vital information about a patient's overall health status, helping identify conditions such as infections, anemias, and blood disorders, and its interpretation should be based on the most recent and highest quality evidence, such as the 2021 guideline by the American Society of Clinical Oncology 1.
Clinical Significance of CBC with Differential
The test evaluates red blood cells (RBCs), white blood cells (WBCs), platelets, and the differential breaks down the types of white blood cells present.
- Hemoglobin and hematocrit levels are assessed to evaluate for anemia (low values) or polycythemia (high values) 1.
- The RBC indices (MCV, MCH, MCHC) help classify anemias as microcytic, normocytic, or macrocytic.
- Total WBC count indicates immune system activity, with elevated counts suggesting infection or inflammation and decreased counts potentially indicating bone marrow suppression or certain viral infections.
- The differential provides percentages of neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specific clinical implications, such as neutrophilia indicating bacterial infection, and lymphocytosis suggesting viral infection 1.
Interpretation and Management
Normal ranges vary by age, sex, and laboratory, so results must be interpreted in the context of the patient's clinical presentation.
- Serial CBCs are often more valuable than single measurements, as they can track disease progression or treatment response.
- Clinicians should always correlate CBC findings with the patient's symptoms, medical history, and other diagnostic tests for accurate diagnosis and treatment planning, as recommended by the 2021 ASCO guideline 1.
- For example, in patients with cytopenia, a CBC with differential, peripheral blood smear, and reticulocyte count should be performed, and further investigation, such as bone marrow evaluation, may be necessary if abnormalities are detected 1.
Key Recommendations
The 2021 ASCO guideline recommends the following management for cytopenia:
- Grade 1: Offer supportive care.
- Grade 2: Offer supportive care and/or consider corticosteroids.
- Grade 3: Provide critical care support and use high-dose methylprednisolone.
- Grade 4: Consider growth factor support for neutrophil recovery, per institutional guidelines 1.
From the Research
Clinical Significance of CBC with Differential
The Complete Blood Count (CBC) with differential is a commonly performed laboratory test that provides valuable information about the production of blood cells and the patient's oxygen-carrying capacity 2. It also offers insights into the immune system through the evaluation of the white blood cell (WBC) count with differential.
Interpretation of CBC Results
The interpretation of CBC results is crucial in diagnosing various medical conditions, including:
- Anemia
- Certain cancers
- Infection
- Acute hemorrhagic states
- Allergies
- Immunodeficiencies 2
- Cardiovascular and metabolic diseases, such as cardiovascular disease (CVD), arteriosclerosis, type 2 diabetes (T2DM), and metabolic syndrome 3
Components of CBC
The components of a CBC include:
- Red blood cell count
- Hemoglobin
- Hematocrit
- Red blood cell indices (including mean cell volume, mean cell hemoglobin, mean cell hemoglobin concentration, and red cell distribution width)
- Reticulocyte count
- White blood cell count and differential
- Platelet count 4
Diagnostic Algorithms
Practical diagnostic algorithms can be used to address frequently encountered conditions associated with CBC abnormalities, including:
- Anemia
- Thrombocytopenia
- Leukopenia
- Polycythemia
- Thrombocytosis
- Leukocytosis 5
Clinical Decision Support
Clinical decision support (CDS) alerts can be effective in reducing unnecessary orders for CBC with differential, improving the quality of patient care, and decreasing turnaround time for manual differentials 6
Key Markers for Disease Prediction
Certain CBC components, such as:
- White blood cell (WBC)
- Neutrophil-to-lymphocyte ratio (NLR)
- Hemoglobin (Hb)
- Mean corpuscular volume (MCV)
- Red cell distribution width (RDW)
- Platelet count
- Mean platelet volume (MPV)
- Platelet-to-lymphocyte ratio (PLR) can be useful markers to predict cardiovascular and metabolic diseases 3