Peripheral blood smear
Author:
Mikael Häggström [note 1]
Look at and comment separately on white blood cells, red blood cells and platelets.
Oil immersion microscopy
This is preferred for light microscopy of peripheral blood smears in order to achieve a very high magnification. First use low or medium power to center on suspicious cells, or where red or white blood cells are best appreciated. Put a drop of immersion oil on the location and switch to the immersion objective. Be systematic in your switching between objectives so as to avoid getting oil on any of your dry objectives (which is a bit tedious to clean off).
Red blood cells
Automated values
When available, automatic quantification of mean corpuscular volume (MCV) and red blood cell (RBC) distribution width (RDW), usually as part of CBC panel, generally decides whether you will call the sample "normocytic" versus "microcytic"/"macrocytic" and/or "anisocytotic", even if it is not clearly visible in the microscope. If automated values are not available, compare RBC sizes to lymphocyte nuclei, which should normally be the same size. If mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) are normal, but you still see multiple RBCs with central pallor greater than 50% of the diameter, you can report it as "Increased central pallor", and you may add "indicating iron deficiency" if it is compatible with the clinical history.
Automated values can be graded as follows:[1]
| Interpretation | Mild | Moderate | Marked |
|---|---|---|---|
| Microcytosis | MCV : 70 - 79 | MCV : 60 - 69 | MCV <60 |
| Macrocytosis | MCV : 100 - 115 | MCV : 115 - 125 | MCV >125 |
| Hypochromasia | MCH : 23 - 26 | MCH : 21 - 23 | MCH <20 |
| Anisocytosis | RDW: 14.5[2] !! Terminology[2] or 16[1] - 18 | RDW : 18 - 22[1] or 26[2] | RDW > 22[1] or 26[2] |
Morphologic findings
Look for poikilocytosis (red blood cells of abnormal shapes):
-
Acanthocytes ("spur cells")
-
Elliptocytes
These are counted as a percentage of visible red blood cells:[1]
| Interpretation | Rare/Occasional | Moderate amount of | Many/Abundant |
|---|---|---|---|
| Polychromasia | 3 - 5% | 5 - 25% | >25% |
| Spherocytes | 1 - 5% | 5 - 25% | >25% |
| Schistocytes | up to 2% | 2 - 25% | >25% |
| Target cells (codocytes) | up to 3% | 3 - 25% | >25% |
| Tear drop cells | up to 2% | 2 - 25% | >25% |
| Burr cells (echinocytes) | 1 - 3% | 3 - 10% | >10% |
| Sickle cells (drepanocytes) | 3 - 5% | 5 - 25% | >25% |
| Elliptocytes | 1 - 5% | 5 - 25% | >25% |
| Basophilic stipplings | up to 2% | 2 - 25% | >25% |
| Howell Jolly bodies | up to 1% | 2 - 3 % | >3% |
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When seeing what appears to a platelet overlying a red blood cells (as pictured), confirm that there is a halo.
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Otherwise, make sure it is not malaria (appearance at different intraerythrocytic blood stages is pictured)...
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...or babesia .
Platelets
If CBC is performed, use count to determine whether platelets are "normal in number" or whether there is "thrombocytopenia" or "thrombocytosis". If no CBC, count platelets within a high power oil immersed field, which should normally be 8 to 20.
In thrombocytopenia from automatic counting, look in particular for:
- Clumping of platelets (which can cause a falsely low automatic platelet count). If present, check with the lab if it was sent in EDTA (which may cause artefactual clumping) and ask to have a blood sample sent in sodium citrate instead. Also, look for satellitosis (platelets attached around white blood cells).
- Schistocytes among red blood cells.
The finding of giant platelets may be reported as "Occasional/multiple giants platelets, which suggests increased platelet turnover".
White blood cells
Look for:
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Blast cells, generally having large nucleus, immature chromatin, a prominent nucleolus, scant cytoplasm and few or no cytoplasmic granules. This example has an Auer rod (to the left of the nucleus).
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Hypersegmented neutrophils. This is abnormal when more than half of neutrophils have at least 4 segments, or more than 5% of neutrophils have more than 5 segments.[3]
![Hypersegmented neutrophils. This is abnormal when more than half of neutrophils have at least 4 segments, or more than 5% of neutrophils have more than 5 segments.[3]](/index.php?title=Special:Upload&wpDestFile=Hypersegmented_neutrophil.jpg){kind=link}
When smudge cells constitute more than 10% of white blood cells, or in patients with CLL, a separate smear with a drop of serum albumin to every four or five drops of blood should be made to stabilize cell membranes.[4] Still evaluate red blood cells and platelets on the non-albumin slide.
Notes
- ↑ For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.
Main page
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Unless otherwise specified in table, reference is:
- . Hong Kong Medical Technology Association - Quality Assurance Programme - Haematology and Serology, Prepared by HKMTAQAP Haematology & Serology Panel on November 2002.. - ↑ 2.0 2.1 2.2 2.3 . High RDW level in the blood. MrLabTest. Last update: 12/01/2021
- ↑ Glassy, Eric (1998). Color atlas of hematology : an illustrated field guide based on proficiency testing . Northfield, Ill: College of American Patholgists. ISBN 978-0-930304-66-9. OCLC 40976106.
- ↑ Error on call to Template:cite web: Parameters url and title must be specifiedFredrick L. Kiechle. . CAP Today. June 2010
Image sources