Introduction
- Blood smears are simple to perform and can provide useful information on all blood cell lines.
- Qualitative (morphology) and quantitative (counts) information can be obtained on leukocytes, erythrocytes and platelet series.
- Definitive diagnosis of blood parasites, eg Hemobartonella felis
. - Characterization of hematological disorders which will assist in definitive diagnosis.
Uses
Indicated in:
- Classify and characterize anemia , bleeding disorders(thrombocytopenia) or neoplasia (leukemia , clinical staging of lymphoma).
- Suspected inflammatory disease (of infectious or immune-mediated origin).
- Suspect cases of infection/parasitic disease including:
- Protozoal parasites: Babesia felis , Cytauxzoon felis .
- Mycoplasma parasites: Mycoplasma haemofelis and Mycoplasma haemominutum (both subspecies of an organism previously known as Haemobartonella felis ).
- Bacteria: Bartonella spp .
- Protozoal parasites: Babesia felis
- As a critical adjunct to in-house hematology analyzers, since differential counts on these machines are only a rough estimation.
Advantages
- Very rapid simple technique requiring minimal equipment.
- Can be performed with very small volumes of blood.
- Accurate assessment of cell morphology which may be affected by storage or transport.
Disadvantages
- Must use clean slides to avoid holes appearing in the smear (grease spots).
- Smear must be rapidly air dried to ensure that cell morphology is preserved.
- Technique must be used regularly to make useful blood smears.
Requirements
Materials required
Minimum equipment
- Microscope with oil-immersion lens for smear examination.
Minimum consumables
- 2 ml syringe and sterile needle.
- Clean glass slides (minimum 2).
- Capillary tube.
- Diff-Quik stain , or suitable alternative (hematology/cytology stains)
Ideal consumables
- Blood tubes containing EDTA anticoagulant.
- Glass slides with frosted end for labeling.
- Spreader slide.
- Romanowsky type stains eg Wrights or Wright- Giemsa, or rapid stain eg Diff Quick (type of Wrights stain) and special stains eg commercial reticulocyte stain or New Methylene blue (to identify reticulocytes)
Preparation
- 5 min for preparation of patient and collection of blood sample.
Sequelae
Reasons for treatment failure
- Collection of sample following multiple attempts at venepuncture may result in falsely depressed platelet counts due to platelet activation and clumping.
- Use of inappropriate anticoagulants or prolonged storage in some anticoagulants may affect cell morphology, eg EDTA can result in platelet clumping, smears should therefore be prepared as soon as possible after blood collection (always check the feathered edge for platelet clumps before performing a platelet count).
- Poor smear technique can result in altered cell morphology and make it difficult to perform cell counts.
- Always use an appropriate stain, eg Diff-Quik is adequate for platelet counts but reticulocytes and Hemobartonella felis organisms will not be seen unless the smear is stained with Giemsa.
