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Published on: September 16, 2012
The complete blood count and leukocyte differential count. An approach to their rational application
Insights
Complete blood count (CBC) and leukocyte differential counts are generally not useful for screening healthy individuals. Limited use cases exist for specific populations or when clinical suspicion is high, guiding targeted diagnostic approaches.
Area of Science:
- Clinical Pathology
- Diagnostic Laboratory Medicine
- Evidence-Based Medicine
Background:
- Complete blood count (CBC) and leukocyte differential counts are common laboratory tests.
- Their utility in routine screening and diagnosis requires critical evaluation.
Purpose of the Study:
- To assess the value of CBC and leukocyte differential counts in various clinical settings.
- To provide evidence-based recommendations for appropriate test utilization.
Main Methods:
- Systematic review of existing literature on CBC and leukocyte differential count utility.
- Analysis of diagnostic yield in asymptomatic individuals, specific populations, and hospitalized patients.
Main Results:
- CBC and leukocyte differential counts lack value for general population screening.
- Potential utility identified for infants, elderly, pregnant women, and immigrants with nutritional concerns.
- Limited value in hospitalized patients unless specific abnormalities or major blood loss are anticipated.
- Leukocyte differential count often unnecessary for confirming infection when leukocytosis is present.
Conclusions:
- Routine screening with CBC and leukocyte differential counts is not recommended for asymptomatic individuals.
- Test utilization should be guided by clinical suspicion and specific patient populations.
- Repeat testing should be judiciously applied based on clinical course and potential impact on decision-making.
Abstract:
The complete blood count and leukocyte differential count have no value in screening asymptomatic members of the general population. The complete blood count may be useful for screening infants in the first year of life, institutionalized elderly persons, pregnant women, and recent immigrants from Third World countries, if poor nutrition or inadequate iron intake is suspected. These tests are not useful for hospitalized patients, unless an abnormality is suspected or surgery with major blood loss is anticipated. It is appropriate to obtain the tests when a hematologic or infectious disorder is suspected, but they may not affect decision making if the diagnosis is clinically evident. The leukocyte differential count is unnecessary to confirm an infection in most cases in which leukocytosis is present. Repeat tests should be limited to situations where the clinical course is unclear, and at intervals long enough such that the results might affect clinical decision making.
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