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Consensus Statements > ACVIM Consensus statement on the diagnosis of immune thrombocytopaenia in dogs and cats > Flashcards

ACVIM Consensus statement on the diagnosis of immune thrombocytopaenia in dogs and cats Flashcards

1
Q

What is the most common acquired primary haemostatic disorder in dogs?

A

Immune thrombocytopaenia (ITP)

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2
Q

What is the mortality rate of ITP in dogs and cats?

A

10 to 30%

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3
Q

Generally, how is ITP diagnosed in dogs and cats?

A

It is a diagnosis of exclusion.

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4
Q

What is thrombopoietin?

A

Glycoprotein hormone produced by the liver and kidney which regulates the production of platelets.

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5
Q

What are the broad types of ITP in dogs and cats?

A

Associative (primary) or non-associative (secondary)

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6
Q

What is thrombocytopaenia?

A

Platelet count < 100,000/uL

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7
Q

What factors can influence the true platelet count in dog and cats?

A
  1. blood draw - platelet activation during blood collection
  2. Pseudothrombocytopaenia - common in cats
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8
Q

Why is pseudothrombocytopaenia common in cats?

A

Because of variable platelet size and relative hyper-reactivity of feline platelets compared with those of other species.

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9
Q

How is thrombocytopaenia confirmed?

A
  1. Slide examination - by a board certified pathologist
  2. Replicate plt count
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10
Q

How do you perform a platelet estimation on a blood smear?

A
  1. Calculate the mean number of platelets per 10 oil immersion fields (×100) in the monolayer
  2. Then multiply this number by 15 000 to 20 000 to obtain the number of platelets per microliter
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11
Q

Describe the algorithm for the diagnosis of ITP in dogs and cats.

A
  1. Confirm thrombocytopaenia with CBC and blood smear
  2. Consider genetic testing for dog predisposed to macrothrombocytes
  3. Exclude cytopaenias e.g. pre-regenerative anaemia, bone marrow sampling
  4. Pt/aPTT, D-dimers, TEG
  5. Screening for potential triggers e.g. UA, imaging, infectious disease testing
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12
Q

Does MPV improve differentiation of ITP from non-immune thrombocytopaenia?

A

There is conflicting evidence in dogs with ITP both decreased, to normal to increased MPV has been observed.

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13
Q

Does reticulated platelets improve differentiation of ITP from non-immune thrombocytopaenia?

A

It can help distinguish between ITP and non-immune thrombocytopaenia. Evidence if weak, however an increased reticulated platelet percentage can be seen in primary ITP

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14
Q

Does plateletcrit improve differentiation of ITP from non-immune thrombocytopaenia?

A

No there is insufficient evidence to make recommendations regarding the use of plateletcrit.

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15
Q

Should MPV, immature platelet fraction and plateletcrit be used as diagnostic tests for ITP?

A

No they should not be used as routine diagnostic tests.

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16
Q

In dogs with confirmed thrombocytopaenia, does severe thrombocytopaenia compared to mild to moderate thrombocytopaenia, improve differentiation of ITP from non-immune thrombocytopaenia?

A

Most evidence suggests the dog with ITP have more severe thrombocytopaenia compared to non-immune thrombocytopaenia but there is overlap between groups. A platelet count of <20000 supports a diagnosis of ITP in dogs but in insufficient to make a diagnosis.

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17
Q

In cats with confirmed thrombocytopaenia, does severe thrombocytopaenia compared to mild to moderate thrombocytopaenia, improve differentiation of ITP from non-immune thrombocytopaenia?

A

In cats there is weak evidence to suggest cats with ITP have more severe thrombocytopaenia compared to non-immune thrombocytopaenia. Again a plt <20000 can only support a diagnosis.

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18
Q

What is the most common cause of PLT < 50000 in cats”?

A

Bone marrow disease, neoplasia or traumatic haemorrhage.

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19
Q

In dogs with primary ITP, does severe thrombocytopaenia compared to mild to moderate thrombocytopaenia impact prediction of bleeding severity, response to first line treatment or platelet count recovery?

A

In dogs with a plt count <50,000 there is moderate evidence to suggest that admission plt count does not impact disease outcome or response.

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20
Q

In cats with primary ITP, does severe thrombocytopaenia compared to mild to moderate thrombocytopaenia impact prediction of bleeding severity, response to first line treatment or platelet count recovery?

A

Unknown. There is insufficient evidence, used of admission platelet count as a prognostic tool is not recommended.

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21
Q

In dogs with confirmed thrombocytopaenia, compared to platelet count alone does the addition of bone marrow examination help differentiate ITP from non-immune thrombocytopaenia?

A

There is insufficient evidence to determine whether bone marrow examination improves the diagnosis of primary ITP in dogs. Thus, bone marrow examination is not recommended as a routine diagnostic test unless additional cytopaenias are present.

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22
Q

In cats with confirmed thrombocytopaenia, compared to platelet count alone does the addition of bone marrow examination help differentiate ITP from non-immune thrombocytopaenia?

A

same as dogs

23
Q

In dogs with confirmed thrombocytopaenia compared with platelet count alone, do platelet/megakaryocyte-associated anti-body assays help differentiate ITP from non-immune thrombocytopaenia?

A

Positive platelet/megakaryocyte-associate antibody tests indicated that an immune component is contributing to thrombocytopaenia but are not diagnostic for ITP. Thus, routine measure of platelet/megakaryocyte-associate antibodies is not recommended.

24
Q

What is PSAIG?

A

Platelet surface associated immunoglobulins.

25
Q

What are the common PSAIG tests?

A
  1. Flow cytometry
  2. Radioimmunoassay
26
Q

In cats with confirmed thrombocytopaenia compared with platelet count alone, do platelet/megakaryocyte-associated anti-body assays help differentiate ITP from non-immune thrombocytopaenia?

A

Routine measurements of PSAIG/megakaryocytes associated auto-anti-bodies in cats is not recommended. It may indicated an immune component but is not diagnostic.

27
Q

In dogs with confirmed thrombocytopaenia compared with platelet count alone, does the addition of coagulation testing, TEG or D-dimer concentration help differentiate ITP from non-immune thrombocytopaenia?

A

APTT and PT is recommended and TEG and D-Dimer should be considered.

28
Q

Why is coagulation testing recommended in cases of ITP?

A

To help differentiate patients with consumptive e.g. DIC and toxic coagulopathies e.g. rodenticide

29
Q

What is the action of anti-coagulant rodenticides?

A

Inhibits vitamin K dependent blood coagulation factors including factors VII, IX and X.

30
Q

In cats with confirmed thrombocytopaenia compared with platelet count alone, does the addition of coagulation testing, TEG or D-dimer concentration help differentiate ITP from non-immune thrombocytopaenia?

A

In cats it is also recommended to performed aPTT and PT. Measurement of TEG and D-dimers can also be considered.

31
Q

In dogs with primary ITP, compared with determination of platelet count alone, does determination of bleeding severity score improve prediction of bleeding severity, responsive to first line treatment, survival, blood product requirement, duration of hospital stay days to platelet recovery or ITP relapse?

A

Severity scoring can be performed to aid in the assessment of disease severity.

32
Q

In dogs does CBC or biochemistry abnormalities improve prediction of severity, response and outcome?

A

High blood urea nitrogen (BUN) and low haematocrit may be associated with increased disease severity in dogs. High BUN can also be associated with poor survival.

33
Q

What are some broad causes of secondary ITP in dogs and cats?

A
  1. Infectious e.g. vector-borne infections, Piroplasms, viral infections,
  2. Neoplasia
  3. Drugs
  4. Toxins
  5. Inflammatory
  6. Vaccine
34
Q

What are the canine vector-borne infections that can causes ITP in dogs? What level of evidence is there to suggest these diseases cause ITP?

A
  1. Ehrlichia - High
  2. Leshimania spp. - High
  3. Anaplasma spp. - Intermediate
35
Q

What are the piroplasms that can cause ITP in dogs? What level of evidence is there to suggest these diseases cause ITP?

A
  1. Babesia spp. - LOW
  2. Rangelia spp. - HIGH
36
Q

Where is rangelia endemic to?

A

South America.

37
Q

What are some other infectious disease that has low/weak evidence of causing secondary ITP?

A
  1. Borrelia burgdorferi
  2. Rickettsia rickettsii
  3. Angiostrongylus vasorum
38
Q

What is the most common viral infection in dogs that can cause ITP? What level of evidence is there to suggest these diseases cause ITP?

A

Canine distemper virus - high

39
Q

What other infections can potentially cause ITP in dogs?

A
  1. Prostatitis
  2. Bacterial abscess or wound infection
  3. Sepsis
40
Q

What are piroplasms?

A

Parasites that are transmitted to animals via ticks.

41
Q

How does Ehrlichia causes thrombocytopaenia?

A

Immune mediated platelet destruction and PSAIG have been detected by flow cytometry. Other mechanisms include splenic sequestration and removal of platelets, vasculitis, hypercoagulability and myelosuppression.

42
Q

What are the mechanisms of action of leishmania spp. in ITP in dogs?

A

Immune mediated platelet destruction as they have have platelet surface associated IgM and IgG detected by flow cytometry. Other mechanisms include vasculitis, bleeding diatheses and bone marrow infectious. Mouse models infected with leishmania showed decrease TPO, decreased bone marrow megakaryocytic maturation and increased splenic and hepatic removal of opsonized and desialylated platelets which contributed to thrombocytopaenia.

43
Q

What are the mechanisms of action of anaplasma spp. in ITP in dogs?

A

Anaplasma phagocytophilium has immunologic mechanism of platelet destruction. We are unsure if A.platys has an immunological mechanism. More research is required.

44
Q

What are the mechanism of action of canine distemper virus in ITP in dogs?

A

Potentially through phagocytosis of platelets with surface-bound virus-antibody immune complexes and decrease platelet production because of megakaryocyte infection with distemper.

45
Q

Can vector borne diseases causes ITP in cats?

A
  1. Ehrlichia - Very limited evidence. Thrombocytopaenia has been documented in cats naturally infected with E. canis.
  2. Leishmania - NO evidence.
  3. Anaplasma - Insufficient evidence. thrombocytopaenia has been documented in cats infected with anaplasma.
46
Q

Can infections e.g. sepsis, abscesses/wounds cause ITP in cats?

A

There is insufficient evidence to make conclusions about the role of infectious causes for ITP in cats.

47
Q

Which drugs can contribute to ITP in dogs? What level of evidence?

A
  1. High level of evdience for cefazedone and gold salts.
  2. Intermediate level for sulfonamides
    3.
48
Q

Which drugs can contribute to ITP in cats? What level of evidence?

A

Low level of evidence for methimazole propylthiouracil.

49
Q

What level of evidence is there to suggest vaccines can cause ITP in dogs?

A

Low.

50
Q

What history should be collected for a suspected ITP?

A
  1. Vaccination status
  2. drugs/medications
  3. access to toxins
  4. Travel exposure
  5. exposure to ticks, flea and other vector
  6. Parasite prevention
  7. Heartworm testing
51
Q

What should laboratory screening at minimum include?

A

CBC and blood smear. Serum biochemistry. urinalysis, urine culture and diagnostic tests to assess for cancer or foci of inflammation e.g. chest rads, abdominal ultrasound.

Faecal float prostatic evaluation in males should also be considered.

52
Q

What are the specific screening recommendation for dogs?

A
  1. Infectious disease testing e.g. serology or PCR
  2. In dog with ITP living in or5 travelling to enzootic areas, especially those with cardiopulmonary disease screening for angiostrongylus vasorum using faecal sedimentation or BAL and PCR should be considered.
  3. In non-under vaccinated dogs canine distemper testing should be considered.
53
Q

What are the specific screening recommended for cats with ITP?

A
  1. FeLV/FIV
  2. CBC/smear
  3. Biochemistry
  4. In cats in enzootic area should be screened for A. phagocytophilium, ehrlichia and B. felis should be considered.

Consensus Statements (2 decks)

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