American Society for Veterinary Clinical Pathology
2424 American Lane
Madison, WI 53704

Telephone: +1-608-443-2479
Fax: +1-608-443-2474

2.3. Hematology

2.3.1. Monitoring - see General recommendations

2.3.2. Method Validation - see General recommendations.  Not all of the method validation experiments listed in section 2.1.2. may be applicable to evaluation of automated hematology analyzers.  Method validation experiments should be selected or modified as necessary to ensure that new methods/analyzers are functioning satisfactorily to meet the laboratory's requirements and the manufacturer's specifications.

2.3.3. Instrumentation - see General recommendations

2.3.4. Personnel Knowledge - see General recommendations

2.3.5. Quality Control for Hematology  - see also General recommendations

a. Automated assays, calculated indices and microscopy

i. Erythrocyte (RBC) count

ii. Hemoglobin concentration

iii. Hematocrit

iv. RBC morphology including RDW, HDW, MCV, MCH/*CH, and MCHC/*CHCM (*direct laser measurement by Advia hematology analyzer)

v. Total leukocyte (WBC) count

vi. WBC differential cell counts (microscopic or automated)

vii. RBC and WBC morphology (microscopic)

viii. Platelet count

ix. Platelet indices including MPV and PCT

x. Reticulocyte counts (microscopic and automated)

xi. Blood smears should be prepared, stained, and held for microscopic examination at the discretion of the clinical pathologist

b. Recommendations 

i. Automated differentials should be verified by manual (microscopic) evaluation of the blood smear.  Establish criteria for situations that require microscopic examination of the blood smear to verify instrument counts (e.g., total WBC count >20,000/μL).

ii. Manual cell counts:  Cell counts performed manually using a hemacytometer must be performed in duplicate.  If there is >10% difference between the counts obtained, the chambers should be reloaded and counted again in duplicate. If a control is used for manual WBC, RBC, or platelet counts, either one level of assayed material or procedural control (defined as following) should be analyzed each time this method is used or once each shift.

i. A procedural control is defined as one of the following:

a. Duplicate dilutions of either assayed control or a previously-assayed patient specimen.  Results may be compared to previously defined acceptable limits for differences between duplicates.  (This is the only acceptable procedural control for manual RBC counts.)

b. WBC and platelet counts may be compared with a value estimated from a peripheral blood smear.

iii. New methylene blue-stained smears may be evaluated for a microscopic reticulocyte count.  If the counts are performed in duplicate (two smears), the results should not differ by >10%.

iv. Automated reticulocyte counts should correlate with proportion of polychromatophilic RBCs observed on a stained blood smear.  

v. Spun hematocrits (PCV) should approximate hematocrit (Hct) calculated by an automated analyzer using MCV and RBC number.  The laboratory should set the maximum acceptable difference, which may vary with species.

vi. Mean cell hemoglobin concentration (MCHC) may exceed the upper reference interval with sample hemolysis (pathologic or in vitro), lipemia and in the presence of Heinz bodies.  In the absence of these conditions, a high MCHC may indicate instrument error. 

2.3.6. Procedures Manual - see General recommendations

2.3.7. Comparison of Tests - see General recommendations

2.3.8. Identification of Out-sourced Tests - see General recommendations