ACVIM consensus statement on the treatment of immune thrombocytopenia in dogs and cats.

Management of immune thrombocytopenia (ITP) in dogs and cats is evolving, but there are no evidence-based guidelines to assist clinicians with treatment decisions. Likewise, the overall goals for treatment of ITP have not been established. Immunosuppressive doses of glucocorticoids are the first line treatment, but optimal treatment regimens beyond glucocorticoids remain uncertain. Additional options include secondary immunosuppressive drugs such as azathioprine, modified cyclosporine, and mycophenolate mofetil, usually selected based on clinician preference. Vincristine, human IV immunoglobulin (hIVIg), and transfusion of platelet or red blood cell-containing products are often used in more severe cases. Splenectomy and thrombopoietin receptor agonists are usually reserved for refractory cases, but when and in which patient these modalities should be employed is under debate. To develop evidence-based guidelines for individualized treatment of ITP patients, we asked 20 Population Intervention Comparison Outcome (PICO) format questions. These were addressed by 17 evidence evaluators using a literature pool of 288 articles identified by a structured search strategy. Evidence evaluators, using panel-designed templates and data extraction tools, summarized evidence and created guideline recommendations. These were integrated by treatment domain chairs and then refined by iterative Delphi survey review to reach consensus on the final guidelines. In addition, 19 non-PICO questions covering scenarios in which evidence was lacking or of low quality were answered by expert opinion using iterative Delphi surveys with panelist integration and refinement. Commentary was solicited from multiple relevant professional organizations before finalizing the consensus. The rigorous consensus process identified few comparative treatment studies, highlighting many areas of ITP treatment requiring additional studies. This statement is a companion manuscript to the ACVIM Consensus Statement on the Diagnosis of Immune Thrombocytopenia in Dogs and Cats.

Canine platelet transfusions.

OBJECTIVE: To review potential platelet storage options, guidelines for administration of platelets, and adverse events associated with platelet transfusions. DATA SOURCES: Data sources included original research publications and scientific reviews. HUMAN DATA SYNTHESIS: Transfusion of platelet concentrates (PCs) plays a key role in the management of patients with severe thrombocytopenia. Currently PCs are stored at 22 degrees C under continuous gentle agitation for up to 5 days. Chilling of platelets is associated with rapid clearance of transfused platelets, and galactosylation of platelets has proven unsuccessful in prolonging platelet survival. Although approved by the American Association of Blood Banks, cryopreservation of human platelets in 6% DMSO largely remains a research technique. Pre-storage leukoreduction of PCs has reduced but not eliminated acute inflammatory transfusion reactions, with platelet inflammatory mediators contributing to such reactions. VETERINARY DATA SYNTHESIS: Canine plateletpheresis allows collection of a concentrate with a high platelet yield, typically 3-4.5 x 10(11) versus <1 x 10(11) for whole blood-derived platelets, improving the ability to provide sufficient platelets to meet the recipient's transfusion needs. Cryopreservation of canine platelets in 6% DMSO offers immediate availability of platelets, with an acceptable posttransfusion in vivo platelet recovery and half-life of 50% and 2 days, respectively. While data on administration of rehydrated lyophilized platelets in bleeding animal models are encouraging, due to a short lifespan (min) posttransfusion, their use will be limited to control of active bleeding, without a sustained increase in platelet count. CONCLUSIONS: Fresh PC remains the product of choice for control of bleeding due to severe thrombocytopenia or thrombopathia. While cryopreservation and lyophilization of canine platelets offer the benefits of immediate availability and long-term storage, the compromise is decreased in vivo recovery and survival of platelets and some degree of impaired function, though such products could still be life saving.

Clinical and clinicopathologic effects of plateletpheresis on healthy donor dogs.

BACKGROUND: The safety and feasibility of plateletpheresis using a commercially available apheresis system (COBE Spectra, Gambro BCT) were evaluated in donor dogs, with characterization of its clinical and clinicopathologic effects. STUDY DESIGN AND METHODS: Fourteen adult dogs (18-27.7 kg) underwent a plateletpheresis procedure. Complete blood counts were obtained at baseline, 2 hours after apheresis, and daily for 1 week. Blood was collected every 15 minutes for acid-base and electrolyte analysis and measurement of serum citrate concentration. Dogs were monitored by continuous electrocardiogram and indirect blood pressure measurement. All dogs received prophylactic calcium (Ca) supplementation (10% Ca gluconate infusion at 15 mL/hr [139.5 mg Ca ion/hr]; the rate was increased based on serial measurement of ionized Ca [iCa] concentration). RESULTS: A high-quality platelet concentrate (PC) was collected, with a mean total yield of 3.3 x 10(11) platelets (PLTs). The mean donor PLT count decreased from 356 x 10(9) to 159 x 10(9) per L after apheresis. The procedure was generally well tolerated, with no evidence of hypotension. Serum citrate concentration progressively increased, causing the ionized magnesium concentration to decrease by 45 percent and iCa to decrease to less than 1 mmol per L (mean baseline, 1.2 mmol/L) in 10 dogs, despite receiving 0.9 mg of Ca ion per mL acid-citrate-dextrose formula A. Lip licking was noted in 3 dogs, and generalized tremors and ventricular ectopy were noted in 1 dog. CONCLUSION: Canine plateletpheresis using the COBE Spectra is a feasible option for production of a PC. Hypocalcemia, however, is a potential serious adverse effect of plateletpheresis in dogs. Ca supplementation is recommended to limit clinical signs of hypocalcemia during the procedure.

Chicken collagen X regulatory sequences restrict transgene expression to hypertrophic cartilage in mice.

Collagen X is produced by hypertrophic cartilage undergoing endochondral ossification. Transgenic mice expressing defective collagen X under the control of 4.7- or 1.6-kb chicken collagen X regulatory sequences yielded skeleto-hematopoietic defects (Jacenko O, LuValle P, Olsen BR: Spondylometaphyseal dysplasia in mice carrying a dominant-negative mutation in a matrix protein specific for cartilage-to-bone transition. Nature 1993, 365:56-61; Jacenko O, Chan D, Franklin A, Ito S, Underhill CB, Bateman JF, Campbell MR: A dominant interference collagen X mutation disrupts hypertrophic chondrocyte pericellular matrix and glycosaminoglycan and proteoglycan distribution in transgenic mice. Am J Pathol 2001, 159:2257-2269; Jacenko O, Roberts DW, Campbell MR, McManus PM, Gress CJ, Tao Z: Linking hematopoiesis to endochondral ossification through analysis of mice transgenic for collagen X. Am J Pathol 2002, 160:2019-2034). Current data indicate that the hematopoietic abnormalities do not result from extraskeletal expression of endogenous collagen X or the transgene. Organs from mice carrying either promoter were screened by immunohistochemistry, in situ hybridization, and Northern blot; transgene and mouse collagen X proteins and messages were detected only in hypertrophic cartilage. Likewise, reverse transcriptase-polymerase chain reaction revealed both transgene and mouse collagen X amplicons only in the endochondral skeleton of mice with the 4.7-kb promoter; however, in mice with the 1.6-kb promoter, multiple organs were transgene-positive. Collagen X and transgene amplicons were also detected in marrow, but likely resulted from contaminating trabecular bone; this was supported by reverse transcriptase-polymerase chain reaction analysis of rat tibial zones free of trabeculae. Our data demonstrate that in mice, the 4.7-kb chicken collagen X promoter restricts transcription temporo-spatially to that of endogenous collagen X, and imply that murine skeleto-hematopoietic defects result from transgene co-expression with collagen X. Moreover, the 4.7-kb hypertrophic cartilage-specific promoter could be used for targeting transgenes to this tissue site in mice.