What is the Buffy coat of a peripheral blood smear?

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Last updated: June 23, 2025View editorial policy

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From the Guidelines

The buffy coat is a thin, whitish-gray layer that forms between the red blood cells and plasma when whole blood is centrifuged, containing white blood cells and platelets, which are less dense than red blood cells but denser than plasma. This layer is particularly useful for detecting abnormalities in white blood cells or platelets when their numbers in circulation are low. The buffy coat typically makes up less than 1% of the total blood volume but contains most of the infection-fighting and clotting components, as noted in the study by 1. Laboratory technicians often use the buffy coat for specialized testing because it provides a higher yield of white blood cells and platelets than would be found in an unconcentrated blood sample, as discussed in 1. Some key points to consider when working with the buffy coat include:

  • It contains a high concentration of white blood cells and platelets, making it useful for detecting abnormalities in these cells.
  • The buffy coat is typically collected after centrifugation of whole blood, as described in 1.
  • It is essential to handle the buffy coat carefully to avoid contamination and ensure accurate test results, as noted in 1 and 1. The concentration effect of the buffy coat makes it easier to identify cellular abnormalities, parasites, or other pathological findings that might be missed in a standard peripheral blood smear, highlighting its importance in laboratory testing, as mentioned in 1.

From the Research

Definition of Buffy Coat

The buffy coat is a component of peripheral blood that is obtained after centrifugation, which separates the blood into its different layers based on density.

Composition of Buffy Coat

It is composed of:

  • White blood cells (including lymphocytes, monocytes, and granulocytes)
  • Platelets
  • Some red blood cells

Uses of Buffy Coat

The buffy coat is used for various purposes, including:

  • Isolation of mononuclear cells (such as lymphocytes and monocytes) for research and clinical applications 2
  • Quantitative analysis of blood components, such as hematocrit value, total WBC count, platelet count, and separation of the leukocyte population into granulocytes and nongranulocytes 3, 4
  • Recovery of leukocytes from leukocyte depletion filters for research applications 5
  • Isolation of hematopoietic progenitor cells from human bone marrow 6

Preparation of Buffy Coat

The buffy coat can be prepared using different methods, including:

  • Centrifugation of whole blood samples in a microhematocrit tube 3, 4
  • Use of a blood cell separator to isolate the buffy coat from whole blood or bone marrow 2, 6
  • Elution of leukocytes from leukocyte depletion filters 5

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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