A complete blood count (CBC) with differential and an additional manual leukocyte differential is a comprehensive laboratory test that evaluates the cellular components of blood. The service includes an automated complete blood count (CBC), ESR (erythrocyte sedimentation rate), and manual differential counting of leukocytes in a blood smear. The test helps assess key red blood cell, white blood cell, and platelet parameters and identify changes that may occur with anemia, infectious, inflammatory, hematologic, and other conditions.
A complete blood count (CBC) is a group of measurements that characterize the three main cellular components of blood: red blood cells, white blood cells, and platelets. Red blood cells transport oxygen, white blood cells are involved in immune defense, and platelets help form blood clots and stop bleeding.
This test may also be referred to as a complete blood count with differential or CBC with differential. The service combines an automated CBC with differential, a manual leukocyte differential, and ESR.
The analyzer measures the number and characteristics of blood cells, calculates indices, and determines the proportions of different types of leukocytes. These same leukocyte types are additionally counted manually by a specialist in a stained blood smear under a microscope. The automated and manual differentials provide numerical results for different types of leukocytes and complement each other.
The results are interpreted together with other CBC parameters, symptoms, and findings from other examinations. The test can identify changes in blood cells but cannot establish a diagnosis on its own.
What parameters are included in a complete blood count with differential?
The service includes three tests: an automated CBC with differential, a manual leukocyte differential, and ESR. The report includes directly measured parameters as well as indices calculated from the measured values.
Red Blood Cell Parameters
Red blood cells (RBCs) are blood cells that transport oxygen from the lungs to the tissues and carry some carbon dioxide back to the lungs. Red blood cell parameters provide information about the number of these cells, hemoglobin level, their average size, and variation in their size. Together, these data help identify signs of anemia and other red blood cell abnormalities.
This group includes:
- red blood cells (RBCs) – the number of red blood cells;
- hemoglobin (HGB) – the protein in red blood cells that carries oxygen;
- hematocrit (HCT) – the proportion of blood volume occupied by red blood cells;
- mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) – calculated indices that characterize red blood cell size and hemoglobin content;
- red cell distribution width (RDW-CV and RDW-SD) – measures of variation in red blood cell size.
White Blood Cells and Leukocyte Differential
White blood cells (WBCs) are immune system cells involved in protecting the body. The total white blood cell count (WBC) indicates the number of white blood cells in the blood sample. The leukocyte differential shows the proportions of the main types of white blood cells:
- neutrophils, which are involved in defense against infections;/li>
- lymphocytes, which are involved in recognizing pathogens, producing antibodies, destroying infected cells, and developing immune memory;/li>
- monocytes, which engulf microorganisms and damaged cells;/li>
- eosinophils, which are involved in allergic reactions and defense against parasites;/li>
- basophils, which are involved in inflammatory and allergic reactions.
The main types of leukocytes are additionally counted manually in a blood smear and reported as numerical values. If atypical, immature, or other cells not included in the standard differential are identified, they are also reported on the laboratory report.
Platelet Parameters
Platelets are small blood components that help form blood clots and stop bleeding after a blood vessel is damaged. As part of a CBC, their number, average size, variation in size, and proportion of total blood volume are assessed.
Platelet parameters include:
- platelets (PLT) – the number of platelets in the blood;
- mean platelet volume (MPV);
- platelet distribution width (PDW);
- plateletcrit (PCT) – the proportion of blood volume occupied by platelets.
A low platelet count may be associated with a tendency to develop bruising or bleeding. At the same time, a CBC does not assess all components of the blood coagulation system, so the results are interpreted together with other parameters and information about the individual’s health.
Erythrocyte Sedimentation Rate
ESR (erythrocyte sedimentation rate) measures how quickly red blood cells settle in a blood sample. This parameter may change in inflammatory, infectious, autoimmune, and other conditions and may also be affected by age, anemia, and other factors.
What does a complete blood count show? Reference ranges and interpretation of results
CBC results reflect changes in blood cells but do not determine their specific cause. Interpretation takes into account the combination of findings:
- low hemoglobin, hematocrit, or red blood cell count may occur with anemia, blood loss, and other conditions;
- changes in MCV, MCH, MCHC, and RDW help assess red blood cells and determine the next steps in the evaluation when anemia is suspected;
- changes in the white blood cell count and leukocyte differential may occur with infectious, inflammatory, allergic, autoimmune, and hematologic conditions;
- changes in the platelet count may occur with various diseases and as a result of medications, but a CBC does not assess all components of the blood coagulation system;
- an elevated ESR may be associated with inflammation, but the test does not indicate a specific disease.
The laboratory provides reference ranges for each parameter on the report. These ranges may vary depending on age, sex, testing method, and laboratory equipment, so the reference ranges provided by the laboratory should be used when interpreting the results.
An abnormality in one or more parameters does not necessarily indicate the presence of a disease, just as results within the reference range do not always rule out an underlying disorder. Results should be interpreted in context, taking into account symptoms, overall health, and findings from other examinations.
