Hematology and Veinpuncture
The hematology branch of clinical laboratory performs the testing on the blood cells, i.e. red blood cells (erythrocytes), white blood cells (leukocytes), and the platelets (thrombocytes). Bone marrow, lymph nodes, and the spleen are the main source of blood cells.
Cells and their constituents, their number or concentration, the relative distribution of different cells, their structural or biochemical abnormalities that contribute to the disease are measured by hematological tests.
A disease can be diagnosed by hematological analysis or the treatment can be monitored by laboratory analysis. Blood disorders can be monitored by hematological manifestations and diseases can have hematological basis. Anemia and enlarged lymph nodes are the examples of symptoms causing many diseases. CBC or complete blood count is the hematological profile generated by automated instruments and it is the basis of initial evaluation and follow-up of the patient
Skin puncture or venipuncture is the primary method collection of specimens for hematology and it is important to show cordial approach to the patient in general. Capillary blood Capillary blood collection can be used for many tests including hemoglobin, microhematocrit, red cell, white cell, and platelet counts. Capillary blood can be also used for the preparation of blood smears for microscopic analysis. It is important not to touch the sampling device to the skin when the tip of the sampling device is placed in the drop of blood when collecting capillary blood.
A glass slide, micropipette, microcuvette can be used as sampling device. An important consideration is the order of draw of blood. Blood films are prepared at the end, and blood for hemoglobin test is collected first followed by cell counts. If platelets are needed, it should be the first test to be done. Pre adequate techniques like adequate mixing of blood with diluting fluid, and knowledge of other collection procedures is important for accurate results.
Venous blood Venous blood sample can be used to do erythrocytes sedimentation rate or ESR, requiring bigger volume of blood and almost all hematological tests. Ethylenediaminetetraacetic acid (EDTA) is the most common anticoagulant used to prevent clotting and to preserve cellular morphology.
Testing cannot be done when even small clots are present and this can be prevented by mixing blood with the anticoagulant by gentle inversion 5 to 10 times immediately after it is collected. Blood samples in EDTA can be used for White cell counts, microhematocrit, platelet counts, and sedimentation rates if it is refrigerated at 4 degree centigrade upto 24hours after collection.
Proper labeling, processing, and transportation of blood sample to the laboratory as quickly as possible, is as important as collection. Collection, laboratory handling, and testing using blood specimens must be done using standard precautions. Proper use of barrier-protective apparel and devices is mandatory since all samples are considered as potentially infectious.
Written by Phlebotomy Training specialist Dr Shahbaz A. Cheema, Course Director for Maxis Healthcare who run NHS Accredited Phlebotomy Training courses for medical and non medical practitioners. Learn the 3 Steps To Become a Phlebotomist
