Slide 1
A blood count measures different cell populations
A complete blood count measures major cellular components of blood. Red cells, white cells and platelets perform different tasks.
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The test includes more than a total cell number. Hemoglobin concentration and the proportion of blood volume occupied by red cells provide additional views of oxygen-carrying tissue.
Slide 2
Red-cell number, size and hemoglobin answer different questions
A red-cell count measures how many cells are present. Hemoglobin and cell-size measurements describe other properties of that population.
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Two samples can have similar cell counts but different amounts of hemoglobin per cell. Looking at related measures together can therefore reveal patterns hidden by a single number.
Slide 3
White-cell types offer further clues
A differential count separates white cells into types. Their relative and absolute numbers provide clues about immune and blood-cell processes.
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A percentage can change because another population changes. Absolute counts help distinguish a true increase in one type from a change in its share of the total.
Slide 4
Platelets are counted separately because their role differs
Platelets are cell fragments involved in limiting bleeding. Their count is one component of a blood count, separate from red and white cells.
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A count does not measure every aspect of platelet function or coagulation. Other tests may be needed when the clinical question concerns how well blood forms a clot.
Slide 5
An unusual pattern can have several explanations
Blood-count results are compared with appropriate reference information. An unusual result can have more than one explanation.
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Age, health history and other findings affect interpretation. Repeated measurements may also show a trend, which is different evidence from one value measured at a single moment.
Sources
- Complete Blood Count (CBC)
MedlinePlus Medical Test
- Blood Differential
MedlinePlus Medical Test