The purpose of this paper by the Regulatory Affairs Committee (RAC) of the American Society for Veterinary Clinical Pathology (ASVCP) is to review the current regulatory guidances (eg, guidelines) and published recommendations for best practices in veterinary toxicologic clinical pathology, particularly in the pharmaceutical and biotechnology industries, and to utilize the combined experience of ASVCP RAC to provide updated recommendations. Discussion points include (1) instrumentation, validation, and sample collection, (2) routine laboratory variables, (3) cytologic laboratory variables, (4) data interpretation and reporting (including peer review, reference intervals and statistics), and (5) roles and responsibilities of clinical pathologists and laboratory personnel. Revision and improvement of current practices should be in alignment with evolving regulatory guidance documents, new technology, and expanding understanding and utility of clinical pathology. These recommendations provide a contemporary guide for the refinement of veterinary toxicologic clinical pathology best practices.

No abstract

| INTRODUC TI ONClinical pathologists working in the industry setting provide specialized expertise in the interpretation of clinical pathology results to support nonclinical animal studies for the purposes of pharmaceutical, agrochemical, food additive, and medical device safety assessment. As the number and complexity of clinical pathology and biomarker assays used in these studies has steadily grown over the last several decades, so has the specialized discipline of Toxicologic Clinical Pathology. Test article-related (TAR) clinical pathology findings must not only be accurately reflected in an interpretive report, but they must also be integrated with other relevant study data (eg, anatomic pathology, in-life, toxicokinetic). Although the task of interpretation of clinical pathology results is sometimes assigned to individuals with little to no formal clinical pathology training, we recommend that clinical pathology interpretive reports be authored by veterinary clinical pathologists with specialized training and experience in toxicologic clinical pathology, especially for pivotal (early and late stage) nonclinical studies. The purpose of this manuscript is to present an overview of current interpretive practices within the pharmaceutical industry and to propose guidelines that will help authors draft accurate, industry-standard clinical pathology interpretive reports. | ROLE AND QUALIFI C ATI ON S OF THE CONTRIBUTING SCIENTIS TClinical pathology evaluations are an integral part of most nonclinical pharmaceutical and agrochemical research projects ranging from proof of concept to general toxicology studies, target animal safety (in the development of animal health products), and medical Abstract The interpretation of clinical pathology results from nonclinical safety studies is a fundamental component in hazard identification of new drug candidates. The everincreasing complexity of nonclinical safety studies and sophistication of modern analytical methods have made the interpretation of clinical pathology information by a highly trained subject matter expert imperative. Certain interpretive techniques are particularly effective in the identification and characterization of clinical pathology effects. The purpose of this manuscript is to provide an overview of contemporary interpretive practices for clinical pathology results and to provide nonbinding recommendations aimed at improving consistency, quality, and overall value of clinical pathology interpretations generated in support of nonclinical toxicology studies.

In preclinical safety assessment, blood volume requirements for various endpoints pose a major challenge. The goal of this working group was to review current practices for clinical pathology (CP) testing in preclinical toxicologic studies, and to discuss advantages and disadvantages of methods for reducing blood volume requirements. An industry-wide survey was conducted to gather information on CP instrumentation and blood collection practices for hematology, clinical biochemistry, and coagulation evaluation in laboratory animals involved in preclinical studies. Based on the survey results and collective experience of the authors, the working group proposes the following "points to consider" for CP testing: (1) For most commercial analyzers, 0.5 mL and 0.8 mL of whole blood are sufficient for hematology and biochemistry evaluation, respectively. (2) Small analyzers with low volume requirements and low throughput have limited utility in preclinical studies. (3) Sample pooling or dilution is inappropriate for many CP methods. (4) Appropriate collection sites should be determined based on blood volume requirements and technical expertise. (5) Microsampling does not provide sufficient volume given current analyzer and quality assurance requirements. (6) Study design considerations include: the use of older/larger animals (rodents), collection of CP samples before toxicokinetic samples, use of separate subsets of mice for hematology and clinical biochemistry testing, use of a priority list for clinical biochemistry, and when possible, eliminating coagulation testing.

Abstract. A straightforward, reliable technique for postcollection processing and evaluation of cytologic specimens for antigen detection using an automated immunostainer was developed. Visual assessment of cell suspension turbidity was used in parallel with light microscopic examination of concentrated cytospin preparations to verify the diagnostic utility of samples for immunocytochemical staining. Fine-needle lymph node biopsies from 81 dogs with lymphadenomegally and a cytologic or histologic diagnosis of lymphoma were introduced into ethylenediamine tetra-acetic acid tubes containing standardized storage media. Cell suspension turbidity was assessed to estimate cell concentration and resultant volume required for cytospin preparations with optimal cellularity. Preliminary cytospin preparations (using estimated volumes based upon turbidity) were stained using modified Wright stain and examined microscopically for intact neoplastic cell concentration. Once an optimal volume for cytospin preparations was established, additional concentrated slides were prepared for immunophenotyping, using an automated immunostainer and antibodies specific for cluster of differentiation (CD)79a and CD3e. All cell suspension samples with adequate gross turbidity had ample intact neoplastic cell concentration for immunocytochemical staining. Based on CD79a and CD3e expression, 51 (63%) B cell, 19 (23%) T cell, 3 mixed T and B cells (4%), and 3 non-T-and non-B-cell lymphomas (4%), as well as 5 (6%) nondiagnostic samples were identified. Three out of 5 of the nondiagnostic samples were submitted early in the investigation prior to the establishment of gross specimen turbidity guidelines. Immunocytochemical staining results were in complete agreement with all 6 available immunohistochemical correlates. The ability to visually assess sample adequacy prior to sample submission may encourage more widespread use of immunocytochemical techniques.