Peripheral blood smear: Difference between revisions

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Look at and comment separately on white blood cells, red blood cells and platelets. You generally don't need to aim for a perfect report, because for most purposes, a peripheral smear is a relatively simple screening test, and clinicians may opt to perform for example flow cytometry and/or a bone marrow biopsy if they want a better evaluation.
{{Comprehensiveness|otherlegend=yes}}
==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. Then, whenever there's oil on a slide, always think twice before switching between objectives so as to avoid getting oil on any of your dry objectives (which is a bit tedious to clean off).


Look at and comment separately on white blood cells, red blood cells and platelets.
==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.


==Red blood cells==
Automated values can be graded as follows:<ref name=HongKong>Unless otherwise specified in table, reference is:<br>- {{cite web|url=http://www.hkimls.org/qapeduhsm-rbc-mor.htm|title=Hong Kong Medical Technology Association - Quality Assurance Programme - Haematology and Serology, Prepared by HKMTAQAP Haematology & Serology Panel on November 2002.}}</ref>
{|class=wikitable align=right
{|class=wikitable
! RDW in adults<ref name=MrLabTest>{{cite web|url=https://www.mrlabtest.com/high-RDW-blood.htm|website=MrLabTest|title=High RDW level in the blood}} Last update: 12/01/2021</ref> !! Terminology<ref name=MrLabTest/>
|-
! Interpretation
! Mild
! Moderate
! Marked
|-
|  Microcytosis ||MCV : 70 - 79||MCV : 60 - 69||MCV <60
|-
|-
| 14.5% - 18% || Mild anisocytosis
| Macrocytosis ||MCV : 100 - 115||MCV : 115 - 125||MCV >125
|-
|-
| 18% - 26% || Moderate anisocytosis
| Hypochromasia||MCH : 23 - 26||MCH : 21 - 23||MCH <20
|-
|-
| > 26% || Severe anisocytosis
| Anisocytosis||RDW: 14.5<ref name=MrLabTest>{{cite web|url=https://www.mrlabtest.com/high-RDW-blood.htm|website=MrLabTest|title=High RDW level in the blood}} Last update: 12/01/2021</ref> or 16<ref name=HongKong/> - 18||RDW : 18 - 22<ref name=HongKong/> or 26<ref name=MrLabTest/> ||RDW > 22<ref name=HongKong/> or 26<ref name=MrLabTest/>
|}
|}
When available automatic quantification of mean corpuscular volume (MCV) and red blood cell 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.


Look for poikilocytosis (red blood cells of abnormal shapes):
===Morphologic findings===
<gallery mode=packed heights=200>
Look for poikilocytosis (red blood cells of abnormal shapes). These are counted as a percentage of visible red blood cells:<ref name=HongKong/>
File:Human blood film with acanthocytes 02.jpg|'''Acanthocytes''' ("spur cells")
{|class=wikitable
File:Micrograph of an echinocyte on a peripheral blood smear.jpg|'''Echinocytes''' ("burr cells"), distinguished from acanthocytes by having more equally distributed and rounded projections. They do not need mention in the report.
|-
File:Micrograph of an elliptocyte on a peripheral blood smear 02.jpg|thumb|'''Elliptocytes'''
|
! Image
! Rare/Occasional
! Moderate amount of
! Many/Abundant
|-
! Polychromasia
| [[File:Peripheral blood smear with polychromasia.jpg|90px]]
|3 - 5%||5 - 25%||>25%
|-
! Spherocytes
| [[File:Micrograph of a spherocyte.jpg|90px]]
|1 - 5%||5 - 25%||>25%
|-
! Schistocytes
| [[File:Micrograph of schistocytes.jpg|90px]]
|up to 2%||2 - 25%||>25%
|-
! Target cells (codocytes)
| [[File:Micrograph of a target cell.jpg|90px]]
|up to 3%||3 - 25%||>25%
|-
! Tear drop cells
| [[File:Micrograph of a tear drop cell (dacrocyte).jpg|90px]]
|up to 2%||2 - 25%||>25%
|-
! Burr cells (echinocytes)
| [[File:Micrograph of an echinocyte on a peripheral blood smear.jpg|90px]]
|1 - 3% || 3 - 10%|| >10%
|-
! Sickle cells (drepanocytes)
| [[File:Micrograph of a sickle cell.jpg|90px]]
|3 - 5%||5 - 25%||>25%
|-
! Elliptocytes
| [[File:Micrograph of an elliptocyte on a peripheral blood smear 02.jpg|90px]]
|1 - 5%||5 - 25%||>25%
|-
! Basophilic stipplings
| [[File:Micrograph of a red blood cell with basophilic stippling.jpg|90px]]
|up to 2%||2 - 25%||>25%
|-
! Howell Jolly bodies
| [[File:Micrograph of a Howell–Jolly body in a red blood cell.jpg|90px]]
|up to 1%||2 - 3 %||>3%
|-
|}
;Burr cells versus spur cells
<gallery mode="packed" heights="150">
File:Micrograph of an echinocyte on a peripheral blood smear.jpg|'''Burr cell''' (echinocyte)
File:Human blood film with acanthocytes 02.jpg|'''Spur cell''' (acanthocyte)
</gallery>
</gallery>
Burr cells are distinguished from spur cells by having more equally distributed and rounded projections. They are usually [[Artifacts|artifactual]]. However, they may also be caused by renal insufficiency, so if this is present, a report may include "Occasional/Multiple echinocytes, consistent with renal insufficiency".


'''Schistocytes''' (fragmented parts red blood cells) only needs mentioning if constituting over 1% of red blood cells or at least 2 per oil immersion field.
;Intraerythrocytic findings
 
<gallery mode="packed" heights="150">
<gallery mode=packed heights=200>
File:Micrograph of a red blood cells with an overlying platelet on a peripheral blood smear.jpg|When seeing what appears to a platelet overlying a red blood cells (as pictured), confirm that there is a halo.
File:Micrograph of a red blood cells with an overlying platelet on a peripheral blood smear.jpg|When seeing what appears to a platelet overlying a red blood cells (as pictured), confirm that there is a halo.
File:Blood stages of P. falciparum over 48h.jpg|Otherwise, make sure it is not '''malaria''' (appearance at different intraerythrocytic blood stages is pictured)...
File:Human blood film with babesia.jpg|Otherwise, make sure it is not '''babesia''' (pictured) or malaria (images below).
File:Human blood film with babesia.jpg|...or babesia.
</gallery>
<gallery mode="packed" heights="250">
File:Blood stages of P. falciparum over 48h.jpg|'''Malaria''', showing appearance at different intraerythrocytic blood stages.
File:Thick blood film with Plasmodium falciparum rings and schizonts.png|If '''malaria''' is suspected, also make a thick blood film.
</gallery>
</gallery>


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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.
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).
[[File:Micrograph of a giant platelet.jpg|thumb|200px|A '''giant platelet'''.]]
'''Large platelets''' are those with a diameter greater than 4 microns. '''Giant platelets''' are those with a diameter greater than 7 microns (larger than a normal red blood cell).<ref name=ash2016>{{cite web|url=https://imagebank.hematology.org/image/60931/giant-platelets?type=upload|title=Giant platelets|website=American Society of Hematology|author=Teresa Scordino|date=2016-12-02}}</ref> Example report:
{|class=wikitable
| Numerous large and giant platelets{{Moderate-begin}}, suggesting an increased platelet turnover{{Moderate-end}}{{Comprehensive-begin}} such as in immune thrombocytopenic purpura. They may also be present in myeloproliferative neoplasms, myelodysplasia, and some congenital thrombocytopenia syndromes, including Bernard-Soulier syndrome and MYH9-related disorders.<ref name=ash2016/>{{Comprehensive-end}}
|}
 
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.


===White blood cells===
===White blood cells===
Look for:
[[File:Monoblast, promonocyte and monocyte.jpg|thumb|400px|Comparison of monoblast, promonocyte and monocyte. {{further|Suspected blasts on peripheral blood smear}}]]
<gallery mode=packed>
A common practice is to evaluate at least 100 white blood cells. Look for:
File:Myeloblast with Auer rod.jpg|thumb|'''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).
<gallery mode="packed" heights="190">
File:Hypersegmented neutrophil.jpg|'''Hypersegmented neutrophil'''. 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.<ref name="Glassy 1998 p. ">{{cite book | last=Glassy | first=Eric | title=Color atlas of hematology : an illustrated field guide based on proficiency testing | publisher=College of American Patholgists | publication-place=Northfield, Ill | year=1998 | isbn=978-0-930304-66-9 | oclc=40976106 | page=}}</ref>
File:Myeloblast with Auer rod.jpg|thumb|'''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). {{further|Suspected blasts on peripheral blood smear}}
File:Hypersegmented neutrophil.jpg|'''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.<ref name="Glassy 1998 p. ">{{cite book | last=Glassy | first=Eric | title=Color atlas of hematology : an illustrated field guide based on proficiency testing | publisher=College of American Patholgists | publication-place=Northfield, Ill | year=1998 | isbn=978-0-930304-66-9 | oclc=40976106 | page=}}</ref>
File:Prolymphocyte in peripheral blood smear.png|In patients with known chronic lymphocytic leukemia, estimate the percentage of '''prolymphocytes''', which are medium-sized lymphocytes with prominent nucleoli.<ref>{{cite web|url=https://imagebank.hematology.org/image/19922/prolymphocytes-in-pll?type=upload|title=prolymphocytes in PLL|website=American Society of Hematology|date=2013-07-16}}</ref> A percentage of less than 5% can be reported as such.
File:Smudge cell in a peripheral blood smear.jpg|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.<ref>{{cite web|url=http://www.captodayonline.com/Archives/0610/0610_qa.html|title=Q & A|website=CAP Today|author=Fredrick L. Kiechle}} June 2010</ref> A semi-quantification of different cell lines should then be made on the albumin slide, whereas white and red blood cell morphology should still be made on the original slide, since it is altered by albumin.
</gallery>
</gallery>
{| class="wikitable" style="text-align:center; vertical-align:middle;"
|+ Atypical/Reactive lymphocytes:<ref name="Nozaka2023">{{cite journal
|last1=Nozaka |first1=Hiroyuki
|last2=Kushibiki |first2=Mihoko
|last3=Kamata |first3=Kosuke
|last4=Yamagata |first4=Kazufumi
|title=Classifying Microscopic Images of Reactive Lymphocytosis Using Two-Step Tandem AI Models
|journal=Applied Sciences
|year=2023
|volume=13
|issue=9
|page=5296
|doi=10.3390/app13095296
|doi-access=free
}} "This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)."</ref>
! rowspan="2" | Morphological feature
! colspan="3" | Atypical lymphocyte<br />— Downey's categorization —
|-
! Type I<br />(monocyte-like)
! Type II<br />(plasma cell-like) - Most common
! Type III<br />(lymphoblast-like)
|-
! Typical morphology
| [[File:Type 1 atypical lymphocyte.png|180px|center|Type I (monocyte-like) atypical lymphocyte]]
| [[File:Type 2 atypical lymphocyte.png|180px|center|Type II (plasma cell-like) atypical lymphocyte]]
| [[File:Type 3 atypical lymphocyte.png|180px|center|Type III (lymphoblast-like) atypical lymphocyte]]
|-
! Size
| ≥16 µm
| ≥16 µm
| ≥16 µm
|-
! Nuclear features
| style="text-align:left;" |
* Kidney-shaped or segmented
| style="text-align:left;" |
* Fine nucleus
* Nucleolus (±)
| style="text-align:left;" |
* Agglutinated chromatin
* Nucleolus (±)
|-
! Cytoplasm
| style="text-align:left;" |
* Strongly basophilic
* Vacuoles (±)
| style="text-align:left;" |
* Strongly basophilic
| style="text-align:left;" |
* Strongly basophilic
|-
! Intracytoplasmic granules
| —
| Azurophilic granules (±)
| —
|}
==Report==
Example report:
{|class=wikitable
| Normochromic normocytic red blood cells. Red blood cells show <normal morphology / anisopoikilocytosis with occasional ___>. {{Comment-begin}}If thrombocytopenia, also add "Schistocytes are not significantly increased" if applicable.{{Comment-end}}
{{Finding-begin}}Leukocytosis with neutrophilia / lymphocytosis.{{Finding-end}} White blood cells show no left shift or blasts.
Platelets show no evidence of clumping, and show normal granularity.
{{Moderate-begin}}Causes of the above findings include ___.{{Moderate-end}}
|}
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