Buffy coat explained

The buffy coat is the fraction of an anticoagulated blood sample that contains most of the leukocytes and thrombocytes following centrifugation.

Description

After centrifugation, one can distinguish a layer of clear fluid (the plasma), a layer of red fluid containing erythrocytes, and a thin layer in between. Composing less than 1% of the total volume of the blood sample, the buffy coat (so-called because it is usually buff in hue), contains most of the leukocytes and thrombocytes.[1] [2] The buffy coat is usually whitish in color, but is sometimes green if the blood sample contains large amounts of neutrophils, which are high in green-colored myeloperoxidase.

The buffy coat is commonly used for DNA extraction,[3] with leukocytes providing approximately 10 times more concentrated sources of nucleated cells.[4] They are extracted from the blood of mammals because mammalian erythrocytes are anucleate and do not contain DNA. A common protocol is to store buffy coat specimens for future DNA isolation and these may remain in frozen storage for many years.[5]

Diagnostic uses

Quantitative buffy coat (QBC), based on the centrifugal stratification of blood components, is a laboratory test for the detection of malarial parasites, as well as of other blood parasites.[6]

The blood is taken in a QBC capillary tube which is coated with acridine orange (a fluorescent dye) and centrifuged; the fluorescing parasitized erythrocytes get concentrated in a layer which can then be observed by fluorescence microscopy,[6] under ultraviolet radiation at the interface between erythrocytes and buffy coat. This test is more sensitive than the conventional thick smear and in over 90% of cases the species of parasite can also be identified.[7] [8]

In cases of extremely low leukocyte count, it may be difficult to perform a manual differential of their various types and it may be virtually impossible to obtain an automated differential. In such cases, the medical technologist may obtain a buffy coat, from which a blood smear is made. This smear contains a much higher number of leukocytes than whole blood.[9]

See also

Notes and References

  1. Book: Mescher . Anthony L. . Junqueira's Basic Histology: Text and Atlas . 2018 . McGraw-Hill Education . 9781260026184 . 237 . 15 . en . Blood.
  2. Book: Marieb, Elaine N. . Human Anatomy & Physiology . Seventh . San Francisco . Pearson Benjamin Cummings . 2007 . 978-0-8053-5910-7 . registration .
  3. Mychaleckyj . Josyf C . Farber . Emily A . Chmielewski . Jessica . Artale . Jamie . Light . Laney S . Bowden . Donald W . Hou . Xuanlin . Marcovina . Santica M . Buffy coat specimens remain viable as a DNA source for highly multiplexed genome-wide genetic tests after long term storage . Journal of Translational Medicine . 10 June 2011 . 9 . 91 . 10.1186/1479-5876-9-91 . 1479-5876. 3128059. 21663644 . free .
  4. Fabre . Anne-Lise . Luis . Aurélie . Colotte . Marthe . Tuffet . Sophie . Bonnet . Jacques . High DNA stability in white blood cells and buffy coat lysates stored at ambient temperature under anoxic and anhydrous atmosphere . PLOS ONE . 30 November 2017 . 12 . 11 . e0188547 . 10.1371/journal.pone.0188547 . 29190767 . 5708797. 2017PLoSO..1288547F . free .
  5. Gustafson . Sarah . Proper . Jacqueline A. . Bowie . E. J. Walter . Sommer . Steve S. . Parameters affecting the yield of DNA from human blood . Analytical Biochemistry . 1 September 1987 . 165 . 2 . 294–299 . 10.1016/0003-2697(87)90272-7 . 3425899 . en . 0003-2697.
  6. Ahmed . Nishat Hussain . Samantaray . Jyotish Chandra . Quantitative Buffy Coat Analysis-An Effective Tool for Diagnosing Blood Parasites . Journal of Clinical and Diagnostic Research . 2014 . 8 . 4 . DH01 . 10.7860/JCDR/2014/7559.4258 . 24959448 . 2249-782X . 4064892.
  7. Book: Sherman . Angel . Medical Parasitology . 2018 . EDTECH . 9781839473531.
  8. Kochareka . Manali . Sarkar . Sougat . Dasgupta . Debjani . Aigal . Umesh . A preliminary comparative report of quantitative buffy coat and modified quantitative buffy coat with peripheral blood smear in malaria diagnosis . Pathogens and Global Health . October 2012 . 106 . 6 . 335–339 . 10.1179/2047773212Y.0000000024 . 23182137 . 4005131.
  9. Book: Blumenreich . Martin S. . The White Blood Cell and Differential Count . Butterworths . 978-0-409-90077-4 . 3rd . 1990 . 21250104 .

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