Thrombocytopenia is a common hematologic abnormality in dogs and can result in clinically relevant bleeding. Underlying mechanisms in thrombocytopenia include decreased platelet production by the bone marrow, increased peripheral destruction, and
thrombocytopenia (23 × 10 9 platelets/L; reference range, 120 to 600 × 10 9 platelets/L). The cat was referred to the Veterinary Teaching Hospital of the Ontario Veterinary College in Guelph, ON, for further evaluation.
At the initial examination, the cat was
Dogs are frequently given chemotherapeutics during the treatment of neoplasia. Thrombocytopenia resulting from chemotherapy-induced myelosuppression is an important adverse effect of such treatment in humans. 1 This undesirable effect is not as
Immune-mediated thrombocytopenia is a common cause of severe thrombocytopenia in dogs. 1 Immune-mediated platelet destruction can be primary with no underlying cause or secondary to drug administration, infection, neoplasia, or blood transfusion
duration. Additionally, thrombocytopenia 12 , 16 and leukocytosis are common findings. 11 To date, no reliable prognostic indicators readily available at presentation have been identified for dogs with splenic HSA treated with surgery and chemotherapy. 17
Objective—To determine accuracy of a manual technique
for detection of neutropenia and thrombocytopenia
in dogs receiving chemotherapy.
Design—Masked prospective study.
Animals—11 dogs treated with chemotherapy for
Procedure—124 blood samples from dogs being
treated with chemotherapy for various neoplasms
were processed through an automated cell counter,
and results were compared with those obtained by
use of a rapid manual technique for estimating neutrophil
and platelet concentrations to determine
whether the manual technique could accurately
detect dogs with neutropenia or thrombocytopenia.
Results—By use of automated techniques, neutropenia
(< 3,000 cells/µl) was detected in 17 of 124 blood
samples, and thrombocytopenia (< 100,000 platelets/µl)
was detected in 3 of 124 blood samples. The manual
technique correctly identified 16 of 17 (94%) blood
samples with neutropenia, with a specificity of 92%
(98/107). The manual technique correctly identified 3 of
3 (100%) blood samples with thrombocytopenia, with
specificity of 94% (114/121).
Conclusions and Clinical Relevance—Manual estimates
of neutrophil and platelet counts are sensitive
and specific; however, a full differential cell count is
still preferable. (J Am Vet Med Assoc 2002;220:1805–1806)
Objective—To evaluate the effect of prednisone alone,
compared with a combination of prednisone and vincristine,
on platelet counts in bleeding dogs with severe
primary immune-mediated thrombocytopenia (IMT).
Design—Prospective case study.
Animals—24 dogs with severe primary IMT.
Procedure—All dogs received immunosuppressive
doses of prednisone (1.5 to 2 mg/kg [0.7 to 0.9 mg/lb]
of body weight, PO, q 12 h). In addition, 12 dogs
received a single dose of vincristine (0.02 mg/kg [0.01
mg/lb], IV). Platelet count, transfusion requirement,
and outcome were monitored. A response was
defined as an increase in platelet count to ≥ 40,000/µl.
Dogs in the prednisone group that failed to respond
received 1 dose of vincristine on day 7.
Results—Dogs that received prednisone and vincristine
had a significantly faster increase in platelet
count to ≥ 40,000/µl than dogs that received prednisone
alone (mean ± SD, 4.9 ± 1.1 vs 6.8 ± 4.5 days,
respectively). A similarly rapid response was observed
in dogs that received vincristine on day 7 after treatment
with prednisone alone failed. Furthermore, duration
of hospitalization was reduced in the vincristine
group, compared with the prednisone group (5.4 ± 0.3
vs 7.3 ± 0.5 days, respectively). No adverse effects
attributable to vincristine were observed in any dog.
Conclusions and Clinical Relevance—Administration
of combined vincristine and prednisone is associated
with more rapid increase in platelet numbers and
shortened duration of hospitalization in dogs with
IMT, compared with use of prednisone alone. Early
use of vincristine seems warranted in dogs with
severe primary IMT. (J Am Vet Med Assoc 2002;