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{{Acute promyelocytic leukemia}}
{{Acute promyelocytic leukemia}}
{{CMG}} {{shyam}}
{{CMG}}; {{AE}} {{shyam}}, {{S.G.}}; {{GRR}} {{Nat}}


==Overview==
==Overview==
The [[Medical laboratory|laboratory]] [[abnormalities]] in acute promyelocytic leukemia can be broadly divided into abnormalities of the complete [[blood]] count and [[abnormalities]] of the [[coagulation]] system. The complete [[blood]] count usually shows [[anemia]], [[thrombocytopenia]], [[leukopenia]], and elevated [[blast]] count. The [[coagulation]] profile usually shows elevated [[prothrombin]] time, elevated partial [[thromboplastin]] time, elevated [[Thrombin clotting time|thrombin time]], elevated reptilase time, and low [[fibrinogen]]. This combination of [[coagulation]] parameters accounts for high [[hemorrhagic]] risk in [[Patient|patients]] with acute promyelocytic leukemia.
The laboratory [[abnormalities]] in acute promyelocytic leukemia can be broadly divided into abnormalities of the complete blood count and abnormalities of the [[coagulation]] system. The complete blood count usually shows [[anemia]], [[thrombocytopenia]], [[leukopenia]], and elevated [[blast]] count. The coagulation profile usually shows elevated [[prothrombin]] time, elevated partial [[thromboplastin]] time, elevated [[Thrombin clotting time|thrombin time]], elevated reptilase time, and low [[fibrinogen]]. This combination of coagulation parameters accounts for high [[hemorrhagic]] risk in patients with acute promyelocytic leukemia.


==Laboratory Findings==
==Laboratory Findings==
===Abnormalities of the complete blood count===
===Abnormalities of the complete blood count===
*'''[[Anemia]]''': [[Anemia]] refers to decreased [[red blood cell]] production, which results in low [[hemoglobin]] content in the peripheral [[blood]]. [[Hemoglobin]] values are typically less than 10 g/dl in most [[Patient|patients]] with acute promyelocytic leukemia. The degree of [[anemia]] corresponds with the amount of [[bone marrow]] [[Infiltration (medical)|infiltration]] by [[leukemic]] [[Cell (biology)|cells]]. [[Patient|Patients]] with severe or advanced [[leukemia]] will usually have severe [[anemia]]. Severe [[anemia]] can result in profound [[fatigue]], [[pallor]], and [[shortness of breath]].<ref name="pmid15356647">{{cite journal |vauthors=Brodsky RA, Jones RJ |title=Riddle: what do aplastic anemia, acute promyelocytic leukemia, and chronic myeloid leukemia have in common? |journal=Leukemia |volume=18 |issue=10 |pages=1740–2 |date=October 2004 |pmid=15356647 |doi=10.1038/sj.leu.2403487 |url=}}</ref><ref name="pmid24466548">{{cite journal |vauthors=Lee HJ, Park HJ, Kim HW, Park SG |title=Comparison of laboratory characteristics between acute promyelocytic leukemia and other subtypes of acute myeloid leukemia with disseminated intravascular coagulation |journal=Blood Res |volume=48 |issue=4 |pages=250–3 |date=December 2013 |pmid=24466548 |pmc=3894382 |doi=10.5045/br.2013.48.4.250 |url=}}</ref><ref name="pmid29071052">{{cite journal |vauthors=Jillella AP, Arellano ML, Heffner LT, Gaddh M, Langston AA, Khoury HJ, Mangoankar A, Kota VK |title=Managing acute promyelocytic leukemia in patients belonging to the Jehovah's Witness congregation |journal=Hematol Rep |volume=9 |issue=3 |pages=7083 |date=September 2017 |pmid=29071052 |pmc=5641824 |doi=10.4081/hr.2017.7083 |url=}}</ref>
*'''Anemia''':
*'''[[Thrombocytopenia]]''': [[Thrombocytopenia]] refers to low [[platelet]] count. The [[platelet]] count is usually less than 150,000 cells per [[microliter]]. Low [[platelet]] count in [[Patient|patients]] with acute promyelocytic leukemia is typically due to two reasons. Firstly, [[leukemic]] [[Cell (biology)|cell]] infiltration in the [[bone marrow]] results in [[Disruption (of schema)|disruption]] of normal [[megakaryocyte]] production with decreased platelet production. Secondly, coagulopathy (disseminated intravascular coagulation) results in platelet consumption and therefore a low [[platelet]] count. This latter reason is unique to acute promyelocytic leukemia compared to other types of leukemia. The degree of [[thrombocytopenia]] also confers [[prognostic]] value in acute promyelocytic leukemia: [[platelet]] counts lower than 40,000 cells per [[microliter]] carries a worse [[prognosis]] than [[platelet]] counts greater than 40,000 [[Cell (biology)|cells]] per [[microliter]].
**[[Anemia]] refers to decreased [[red blood cell]] production, which results in low [[hemoglobin]] content in the [[peripheral blood]]. [[Hemoglobin]] values are typically less than 10 g/dl in most patients with acute promyelocytic leukemia. The degree of anemia corresponds with the amount of [[bone marrow]] [[Infiltration (medical)|infiltration]] by [[leukemic]] [[Cell (biology)|cells]]. Patients with severe or advanced leukemia will usually have severe anemia. Severe anemia can result in profound [[fatigue]], [[pallor]], and [[shortness of breath]].<ref name="pmid15356647">{{cite journal |vauthors=Brodsky RA, Jones RJ |title=Riddle: what do aplastic anemia, acute promyelocytic leukemia, and chronic myeloid leukemia have in common? |journal=Leukemia |volume=18 |issue=10 |pages=1740–2 |date=October 2004 |pmid=15356647 |doi=10.1038/sj.leu.2403487 |url=}}</ref><ref name="pmid24466548">{{cite journal |vauthors=Lee HJ, Park HJ, Kim HW, Park SG |title=Comparison of laboratory characteristics between acute promyelocytic leukemia and other subtypes of acute myeloid leukemia with disseminated intravascular coagulation |journal=Blood Res |volume=48 |issue=4 |pages=250–3 |date=December 2013 |pmid=24466548 |pmc=3894382 |doi=10.5045/br.2013.48.4.250 |url=}}</ref><ref name="pmid29071052">{{cite journal |vauthors=Jillella AP, Arellano ML, Heffner LT, Gaddh M, Langston AA, Khoury HJ, Mangoankar A, Kota VK |title=Managing acute promyelocytic leukemia in patients belonging to the Jehovah's Witness congregation |journal=Hematol Rep |volume=9 |issue=3 |pages=7083 |date=September 2017 |pmid=29071052 |pmc=5641824 |doi=10.4081/hr.2017.7083 |url=}}</ref>
*'''[[Leukopenia]]''': [[Leukopenia]] refers to [[white blood cell]] count below 4,000 [[Cell (biology)|cells]] per [[microliter]]. [[Leukopenia]] is common in [[Patient|patients]] with acute promyelocytic leukemia, unlike most other types of [[leukemia]]. In some cases, however, [[Patient|patients]] can have high [[white blood cell]] counts, which confers a worse [[prognosis]]. [[White blood cell]] count above 10,000 cells per [[microliter]] defines high-risk [[disease]].
*'''Thrombocytopenia''':
*'''[[Elevated blast count]]''': The [[white blood cell]] differential will typically show the presence of circulating [[blasts]], which are the [[malignant]] [[Cell (biology)|cells]] in acute promyelocytic leukemia. An elevated peripheral [[blood]] [[blast]] count is a common initial finding in the [[disease]], and this finding frequently serves as the trigger for additional workup. The presence of peripheral [[blood]] blasts must be evaluated further by performing a [[bone marrow]] [[biopsy]].
**[[Thrombocytopenia]] refers to low [[platelet]] count. The platelet count is usually less than 150,000 cells per microliter. Low platelet count in patients with acute promyelocytic leukemia is typically due to two reasons.<ref name="QianWen-jun20132">{{cite journal|last1=Qian|first1=Xu|last2=Wen-jun|first2=Liu|title=Platelet Changes in Acute Leukemia|journal=Cell Biochemistry and Biophysics|volume=67|issue=3|year=2013|pages=1473–1479|issn=1085-9195|doi=10.1007/s12013-013-9648-y}}</ref>
**Firstly, leukemic cell infiltration in the [[bone marrow]] results in disruption of normal [[megakaryocyte]] production with decreased platelet production. Secondly, [[coagulopathy]] (disseminated intravascular coagulation) results in platelet consumption and therefore a low platelet count. This latter reason is unique to acute promyelocytic leukemia compared to other types of leukemia. The degree of thrombocytopenia also confers [[prognostic]] value in acute promyelocytic leukemia: platelet counts lower than 40,000 cells per microliter carries a worse prognosis than platelet counts greater than 40,000 cells per microliter.<ref name="QianWen-jun2013">{{cite journal|last1=Qian|first1=Xu|last2=Wen-jun|first2=Liu|title=Platelet Changes in Acute Leukemia|journal=Cell Biochemistry and Biophysics|volume=67|issue=3|year=2013|pages=1473–1479|issn=1085-9195|doi=10.1007/s12013-013-9648-y}}</ref>
*'''Leukopenia''':
**[[Leukopenia]] refers to [[white blood cell]] count below 4,000 cells per microliter. Leukopenia is common in patients with acute promyelocytic leukemia, unlike most other types of [[leukemia]].<ref name="McDonnellSmith2017">{{cite journal|last1=McDonnell|first1=Megan H.|last2=Smith|first2=Elton T.|last3=Lipford|first3=Edward H.|last4=Gerber|first4=Jonathan M.|last5=Grunwald|first5=Michael R.|title=Microgranular acute promyelocytic leukemia presenting with leukopenia and an unusual immunophenotype|journal=Hematology/Oncology and Stem Cell Therapy|volume=10|issue=1|year=2017|pages=35–38|issn=16583876|doi=10.1016/j.hemonc.2015.12.004}}</ref>
**In some cases, however, patients can have high white blood cell counts, which confers a worse prognosis. White blood cell count above 10,000 cells per microliter defines high-risk disease.<ref name="KelaidiAdes2011">{{cite journal|last1=Kelaidi|first1=Charicleia|last2=Ades|first2=Lionel|last3=Fenaux|first3=Pierre|title=TREATMENT OF ACUTE PROMYELOCYTIC LEUKEMIA WITH HIGH WHITE CELL BLOOD COUNTS.|journal=Mediterranean Journal of Hematology and Infectious Diseases|volume=3|issue=1|year=2011|pages=e2011038|issn=2035-3006|doi=10.4084/mjhid.2011.038}}</ref>
*'''[[Elevated blast count]]''':
**The white blood cell differential will typically show the presence of circulating [[blasts]], which are the [[malignant]] cells in acute promyelocytic leukemia.<ref name="Chabot-RichardsGeorge2014">{{cite journal|last1=Chabot-Richards|first1=D. S.|last2=George|first2=T. I.|title=Leukocytosis|journal=International Journal of Laboratory Hematology|volume=36|issue=3|year=2014|pages=279–288|issn=17515521|doi=10.1111/ijlh.12212}}</ref>
**An elevated peripheral blood blast count is a common initial finding in the disease, and this finding frequently serves as the trigger for additional workup. The presence of peripheral blood blasts must be evaluated further by performing a bone marrow [[biopsy]].<ref name="PercivalLai2017">{{cite journal|last1=Percival|first1=Mary-Elizabeth|last2=Lai|first2=Catherine|last3=Estey|first3=Elihu|last4=Hourigan|first4=Christopher S.|title=Bone marrow evaluation for diagnosis and monitoring of acute myeloid leukemia|journal=Blood Reviews|volume=31|issue=4|year=2017|pages=185–192|issn=0268960X|doi=10.1016/j.blre.2017.01.003}}</ref>


===Abnormalities of coagulation parameters===
===Abnormalities of coagulation parameters===
*'''[[Hypofibrinogenemia]]''': [[Hypofibrinogenemia]], or [[fibrinogen]] level below 100 mg/dl, is commonly found in [[Patient|patients]] with acute promyelocytic leukemia. [[Hypofibrinogenemia]] is a key component of disseminated [[intravascular]] [[coagulation]], which is characterized by widespread clot formation and breakdown. [[Fibrinogen]], also known as factor I of the [[coagulation]] cascade, is broken down in [[Patient|patients]] with acute promyelocytic leukemia, resulting in [[bleeding]] [[Complication (medicine)|complications]]. Values of less than 100 mg/dl require treatment with [[cryoprecipitate]], which restores [[fibrinogen]] levels towards normal range.<ref name="pmid16504043">{{cite journal| author=Franchini M, Lippi G, Manzato F| title=Recent acquisitions in the pathophysiology, diagnosis and treatment of disseminated intravascular coagulation. | journal=Thromb J | year= 2006 | volume= 4 | issue=  | pages= 4 | pmid=16504043 | doi=10.1186/1477-9560-4-4 | pmc=1402263 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16504043  }} </ref>
*'''Hypofibrinogenemia''':
*'''Elevated [[prothrombin time (PT)]]''': High [[Prothrombin time|PT]] values, typically above 15 seconds, are common in patients with acute promyelocytic leukemia. This is due to [[disseminated intravascular coagulation]], which results in [[Coagulopathy|consumption]] of [[coagulation]] factors of the intrinsic and extrinsic [[coagulation]] pathways. High PT reflects consumption of factors from the extrinsic pathway, such as [[factor VII]].<ref name="pmid16504043">{{cite journal| author=Franchini M, Lippi G, Manzato F| title=Recent acquisitions in the pathophysiology, diagnosis and treatment of disseminated intravascular coagulation. | journal=Thromb J | year= 2006 | volume= 4 | issue=  | pages= 4 | pmid=16504043 | doi=10.1186/1477-9560-4-4 | pmc=1402263 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16504043  }} </ref>
**[[Hypofibrinogenemia]], or a [[fibrinogen]] level below 100 mg/dl, is commonly found in patients with acute promyelocytic leukemia. Hypofibrinogenemia is a key component of disseminated intravascular coagulation, which is characterized by widespread clot formation and breakdown. [[Fibrinogen]], also known as [[factor I]] of the [[coagulation cascade]], is broken down in patients with acute promyelocytic leukemia, resulting in bleeding complications. Values of less than 100 mg/dl require treatment with [[cryoprecipitate]], which restores [[fibrinogen]] levels towards normal range.<ref name="pmid16504043">{{cite journal| author=Franchini M, Lippi G, Manzato F| title=Recent acquisitions in the pathophysiology, diagnosis and treatment of disseminated intravascular coagulation. | journal=Thromb J | year= 2006 | volume= 4 | issue=  | pages= 4 | pmid=16504043 | doi=10.1186/1477-9560-4-4 | pmc=1402263 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16504043  }} </ref>
*'''Elevated [[partial thromboplastin time (PTT)]]''': High [[Partial thromboplastin time|PTT]] values, typically above 40 second, are common in [[Patient|patients]] with acute promyelocytic leukemia. This is due to [[disseminated intravascular coagulation]], which results in [[Consumption coagulopathy|consumption of coagulation]] factors of the intrinsic and extrinsic [[coagulation]] pathways. High [[Partial thromboplastin time|PTT]] reflects consumption of factors from the intrinsic pathway, such as factors [[Facror XII|XII]], [[Factor XI|XI]], [[Factor IX|IX]], and [[Factor VIII|VIII]].<ref name="pmid16504043">{{cite journal| author=Franchini M, Lippi G, Manzato F| title=Recent acquisitions in the pathophysiology, diagnosis and treatment of disseminated intravascular coagulation. | journal=Thromb J | year= 2006 | volume= 4 | issue=  | pages= 4 | pmid=16504043 | doi=10.1186/1477-9560-4-4 | pmc=1402263 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16504043  }} </ref>
*'''Elevated prothrombin time (PT)''':  
*'''Elevated [[thrombin time]]''': [[Thrombin]] time measures the conversion of [[fibrinogen]] to [[fibrin]], and therefore a high [[thrombin]] time is seen in [[Patient|patients]] with [[coagulopathy]] from acute promyelocytic leukemia. [[Thrombin]] is also known as [[factor II]] of the [[coagulation]] cascade and is immediately upstream of [[fibrinogen]].<ref name="pmid16504043">{{cite journal| author=Franchini M, Lippi G, Manzato F| title=Recent acquisitions in the pathophysiology, diagnosis and treatment of disseminated intravascular coagulation. | journal=Thromb J | year= 2006 | volume= 4 | issue=  | pages= 4 | pmid=16504043 | doi=10.1186/1477-9560-4-4 | pmc=1402263 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16504043  }} </ref>
**High [[Prothrombin time|PT]] values, typically above 15 seconds, are common in patients with acute promyelocytic leukemia. This is due to [[disseminated intravascular coagulation]], which results in consumption of [[coagulation factors]] of the intrinsic and extrinsic coagulation pathways. High PT reflects consumption of factors from the extrinsic pathway, such as [[factor VII]].<ref name="pmid16504043">{{cite journal| author=Franchini M, Lippi G, Manzato F| title=Recent acquisitions in the pathophysiology, diagnosis and treatment of disseminated intravascular coagulation. | journal=Thromb J | year= 2006 | volume= 4 | issue=  | pages= 4 | pmid=16504043 | doi=10.1186/1477-9560-4-4 | pmc=1402263 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16504043  }} </ref>
*'''Elevated [[reptilase time]]''': Reptilase time also measures the conversion of [[fibrinogen]] to [[fibrin]], but this test uses a different [[enzyme]], known as reptilase, which is derived from [[Snake venoms|snake venom]]. The unique feature of the reptilase time is that it can be used to [[differentiate]] high [[Partial thromboplastin time|PTT]] caused by [[heparin]] effect: the reptilase time is not sensitive to [[heparin]]. Reptilase time is high in [[Patient|patients]] with [[coagulopathy]] from acute promyelocytic leukemia.
*'''Elevated [[partial thromboplastin time (PTT)]]''':  
*'''Elevated [[D-dimer]]''': [[D-dimer]] measures simulataneous [[clot]] formation and breakdown. Elevated D-dimer is not specific to acute promyelocytic leukemia, as it can be found in [[Patient|patients]] with [[Obstetrics|obstetric]] [[Complication (medicine)|complications]] ([[eclampsia]] and [[amniotic fluid embolism]]) or [[sepsis]] from ''[[Neisseria meningitidis|Neisseria meningitides]]''. Elevated [[D-dimer]] is very sensitive for an underlying [[coagulopathy]] and is an excellent test for ruling out a [[hematologic]] condition is the pre-test probability is low. [[D-dimer]] is elevated in the majority of cases of acute promyelocytic leukemia.<ref name="pmid23049403">{{cite journal| author=Bassi SC, Rego EM| title=Molecular basis for the diagnosis and treatment of acute promyelocytic leukemia. | journal=Rev Bras Hematol Hemoter | year= 2012 | volume= 34 | issue= 2 | pages= 134-9 | pmid=23049403 | doi=10.5581/1516-8484.20120033 | pmc=3459394 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23049403  }} </ref>
**High [[Partial thromboplastin time|PTT]] values, typically above 40 second, are common in patients with acute promyelocytic leukemia. This is due to [[disseminated intravascular coagulation]], which results in [[Consumption coagulopathy|consumption of coagulation]] factors of the intrinsic and extrinsic coagulation pathways. High [[Partial thromboplastin time|PTT]] reflects consumption of factors from the intrinsic pathway, such as factors XII, [[Factor XI|XI]], [[Factor IX|IX]], and [[Factor VIII|VIII]].<ref name="pmid16504043">{{cite journal| author=Franchini M, Lippi G, Manzato F| title=Recent acquisitions in the pathophysiology, diagnosis and treatment of disseminated intravascular coagulation. | journal=Thromb J | year= 2006 | volume= 4 | issue=  | pages= 4 | pmid=16504043 | doi=10.1186/1477-9560-4-4 | pmc=1402263 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16504043  }} </ref>
*'''Elevated thrombin time''':
**[[Thrombin]] time measures the conversion of [[fibrinogen]] to [[fibrin]]; therefore, a high thrombin time is seen in patients with coagulopathy from acute promyelocytic leukemia. Thrombin is also known as [[factor II]] of the coagulation cascade and is immediately upstream of fibrinogen.<ref name="pmid16504043">{{cite journal| author=Franchini M, Lippi G, Manzato F| title=Recent acquisitions in the pathophysiology, diagnosis and treatment of disseminated intravascular coagulation. | journal=Thromb J | year= 2006 | volume= 4 | issue=  | pages= 4 | pmid=16504043 | doi=10.1186/1477-9560-4-4 | pmc=1402263 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16504043  }} </ref>
*'''Elevated [[reptilase time]]''':
**Reptilase time also measures the conversion of [[fibrinogen]] to [[fibrin]], but this test uses a different enzyme, known as reptilase, which is derived from [[Snake venoms|snake venom]]. The unique feature of the reptilase time is that it can be used to differentiate high [[Partial thromboplastin time|PTT]] caused by [[heparin]] effect. The reptilase time is not sensitive to [[heparin]].<ref name="Karapetian2013">{{cite journal|last1=Karapetian|first1=Hratsch|title=Reptilase Time (RT)|volume=992|year=2013|pages=273–277|issn=1064-3745|doi=10.1007/978-1-62703-339-8_20}}</ref>
**Reptilase time is high in patients with coagulopathy from acute promyelocytic leukemia.<ref name="WheelerRice2010">{{cite journal|last1=Wheeler|first1=Arthur P.|last2=Rice|first2=Todd W.|title=Coagulopathy in Critically III Patients|journal=Chest|volume=137|issue=1|year=2010|pages=185–194|issn=00123692|doi=10.1378/chest.08-2535}}</ref>
*'''Elevated D-dimer''':  
**[[D-dimer]] measures simultaneous [[clot]] formation and breakdown. Elevated D-dimer is not specific to acute promyelocytic leukemia, as it can be found in patients with [[Obstetrics|obstetric]] complications ([[eclampsia]] and [[amniotic fluid embolism]]) or [[sepsis]] from ''[[Neisseria meningitidis|Neisseria meningitides]]''. Elevated D-dimer is very sensitive for an underlying coagulopathy and is an excellent test for ruling out a [[hematologic]] condition, if the pre-test probability is low. D-dimer is elevated in the majority of cases of acute promyelocytic leukemia.<ref name="pmid23049403">{{cite journal| author=Bassi SC, Rego EM| title=Molecular basis for the diagnosis and treatment of acute promyelocytic leukemia. | journal=Rev Bras Hematol Hemoter | year= 2012 | volume= 34 | issue= 2 | pages= 134-9 | pmid=23049403 | doi=10.5581/1516-8484.20120033 | pmc=3459394 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23049403  }} </ref>


==References==
==References==

Latest revision as of 13:12, 11 April 2019

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Shyam Patel [2], Sogand Goudarzi, MD [3]; Grammar Reviewer: Natalie Harpenau, B.S.[4]

Overview

The laboratory abnormalities in acute promyelocytic leukemia can be broadly divided into abnormalities of the complete blood count and abnormalities of the coagulation system. The complete blood count usually shows anemia, thrombocytopenia, leukopenia, and elevated blast count. The coagulation profile usually shows elevated prothrombin time, elevated partial thromboplastin time, elevated thrombin time, elevated reptilase time, and low fibrinogen. This combination of coagulation parameters accounts for high hemorrhagic risk in patients with acute promyelocytic leukemia.

Laboratory Findings

Abnormalities of the complete blood count

  • Anemia:
  • Thrombocytopenia:
    • Thrombocytopenia refers to low platelet count. The platelet count is usually less than 150,000 cells per microliter. Low platelet count in patients with acute promyelocytic leukemia is typically due to two reasons.[4]
    • Firstly, leukemic cell infiltration in the bone marrow results in disruption of normal megakaryocyte production with decreased platelet production. Secondly, coagulopathy (disseminated intravascular coagulation) results in platelet consumption and therefore a low platelet count. This latter reason is unique to acute promyelocytic leukemia compared to other types of leukemia. The degree of thrombocytopenia also confers prognostic value in acute promyelocytic leukemia: platelet counts lower than 40,000 cells per microliter carries a worse prognosis than platelet counts greater than 40,000 cells per microliter.[5]
  • Leukopenia:
    • Leukopenia refers to white blood cell count below 4,000 cells per microliter. Leukopenia is common in patients with acute promyelocytic leukemia, unlike most other types of leukemia.[6]
    • In some cases, however, patients can have high white blood cell counts, which confers a worse prognosis. White blood cell count above 10,000 cells per microliter defines high-risk disease.[7]
  • Elevated blast count:
    • The white blood cell differential will typically show the presence of circulating blasts, which are the malignant cells in acute promyelocytic leukemia.[8]
    • An elevated peripheral blood blast count is a common initial finding in the disease, and this finding frequently serves as the trigger for additional workup. The presence of peripheral blood blasts must be evaluated further by performing a bone marrow biopsy.[9]

Abnormalities of coagulation parameters

  • Hypofibrinogenemia:
    • Hypofibrinogenemia, or a fibrinogen level below 100 mg/dl, is commonly found in patients with acute promyelocytic leukemia. Hypofibrinogenemia is a key component of disseminated intravascular coagulation, which is characterized by widespread clot formation and breakdown. Fibrinogen, also known as factor I of the coagulation cascade, is broken down in patients with acute promyelocytic leukemia, resulting in bleeding complications. Values of less than 100 mg/dl require treatment with cryoprecipitate, which restores fibrinogen levels towards normal range.[10]
  • Elevated prothrombin time (PT):
  • Elevated partial thromboplastin time (PTT):
  • Elevated thrombin time:
    • Thrombin time measures the conversion of fibrinogen to fibrin; therefore, a high thrombin time is seen in patients with coagulopathy from acute promyelocytic leukemia. Thrombin is also known as factor II of the coagulation cascade and is immediately upstream of fibrinogen.[10]
  • Elevated reptilase time:
    • Reptilase time also measures the conversion of fibrinogen to fibrin, but this test uses a different enzyme, known as reptilase, which is derived from snake venom. The unique feature of the reptilase time is that it can be used to differentiate high PTT caused by heparin effect. The reptilase time is not sensitive to heparin.[11]
    • Reptilase time is high in patients with coagulopathy from acute promyelocytic leukemia.[12]
  • Elevated D-dimer:
    • D-dimer measures simultaneous clot formation and breakdown. Elevated D-dimer is not specific to acute promyelocytic leukemia, as it can be found in patients with obstetric complications (eclampsia and amniotic fluid embolism) or sepsis from Neisseria meningitides. Elevated D-dimer is very sensitive for an underlying coagulopathy and is an excellent test for ruling out a hematologic condition, if the pre-test probability is low. D-dimer is elevated in the majority of cases of acute promyelocytic leukemia.[13]

References

  1. Brodsky RA, Jones RJ (October 2004). "Riddle: what do aplastic anemia, acute promyelocytic leukemia, and chronic myeloid leukemia have in common?". Leukemia. 18 (10): 1740–2. doi:10.1038/sj.leu.2403487. PMID 15356647.
  2. Lee HJ, Park HJ, Kim HW, Park SG (December 2013). "Comparison of laboratory characteristics between acute promyelocytic leukemia and other subtypes of acute myeloid leukemia with disseminated intravascular coagulation". Blood Res. 48 (4): 250–3. doi:10.5045/br.2013.48.4.250. PMC 3894382. PMID 24466548.
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