November 21, 2019 -- Hematology is the study of peripheral blood and bone marrow cells in order to diagnose various diseases of the blood, including leukemias, anemia, and autoimmune diseases.
The basis of hematology testing is the complete blood count (CBC), which provides information on blood components: hemoglobin, hematocrit, red blood cells, white blood cells, reticulocytes, and platelets. The CBC is run as part of the normal workup in an annual health exam and for every inpatient. A drop of blood is placed on a microscope slide and stained. The slide is then examined under a microscope and the cells are analyzed.
Hematology will remain the second-largest volume of global IVD procedures, with the number of tests increasing 5.3% per year to nearly 6.7 billion in 2024. Growth in related IVD product sales during the same time frame will expand 5.5% annually to more than $5.6 billion.
The menu of hematology tests includes CBC + 5-part differential (or 3-part differential), manual differential/review, hematocrit, hemoglobin (automated, manual), sedimentation rate, reticulocyte count, white blood cell (WBC) count, platelet count and analysis, and red blood cell (RBC) count.
There is continued discussion as to the need for a full 5-part differential versus a 3-part differential. White blood cells, or leukocytes, are the immune system's primary defense against infection and disease. Therefore, measuring the level of white blood cells in blood enables clinicians to easily detect and monitor various conditions.
The 3-part differential provides a WBC count based on three categories: granulocytes, monocytes, and lymphocytes. The 5-part provides a more advanced WBC count of neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
Each WBC type serves a different function, which is why most laboratories prefer a broader count. Lymphocytes attack specific viruses and bacteria; neutrophils combat bacteria; eosinophils target parasites and certain infections; monocytes respond to inflammation and replenish white blood cells in bodily tissue; and basophils, the rarest type, attack certain parasites. All high-volume systems provide at least a 5-part differential and many smaller instruments do as well.
However, depending on the facility's level of expertise and budget, a 3-part differential may fulfill its needs. In fact, vendors are still marketing 3-part instruments with sophisticated sample management enhancements.
Today and over the past 50 years, the CBC has made an enormous impact on patient care. A CBC is run on every hospitalized patient, and it is a vital part of a yearly annual checkup. The information clinicians derive from the CBC is used in the evaluation of just about every medical condition.
Over the years, hematology cell counting progressed from impedance-based technology (the basis of the Coulter principle) by borrowing from flow cytometry. The incorporation of laser excitation and fluorescence detection into the hematology analyzer has grown the instruments' cell discrimination abilities to include blood cell components that required labor intensive and inexact manual methods. This one significant addition also created automated flow cytometers for the hematology laboratory.
Hematology analyzer product differentiation is accomplished by adding new parameters to a basic instrument -- such as platelet counting, reticulocyte counting, and CD4/CD8 analysis. The second approach is expansion into body fluids other than blood. The third avenue for differentiation is in automation strategies that include integration onto a core lab automation track, the addition of an automated slide maker and stainer, cell imaging technology, and bioinformatic software. These strategies have already been put in place by all of the players.
Thus, hematology vendors have perfected high-end hematology analyzers to perform a number of specialized tests that are now available on-demand and almost instantaneously. Using the cell staining and counting capabilities of high-end hematology analyzers allows labs to automate fluid analyses such as cerebrospinal fluid (CSF) testing. Abbott Diagnostics, Beckman Coulter/Danaher, Siemens Healthineers, and Horiba offer specialized platelet, RBC, and WBC analysis and automatic slide makers/stainers. This feature decreases the number of differential slides that have to be made to only those samples with really abnormal cells.
Rise of professional POC
The total worldwide volume of point-of-care (POC) professional hematology testing procedures conducted is predicted to expand 4.4% annually to 424 million in 2024. Uses in general health screening and the diagnosis and monitoring of blood-related disorders during hospital stays, emergency room visits, and physician consultations will account for growth. The availability of complete blood counts on high-throughput clinical chemistry systems will moderate a faster rise in procedure volume.
Other POC professional hematology procedures include hemoglobin and hematocrit tests. Hemoglobin is a protein in red blood cells that carries oxygen to organs and tissues and transports carbon dioxide from organs and tissues back to the lungs. A low level of this substance is a symptom of anemia. An excessive level of hemoglobin indicates that the patient may have the blood disorder polycythemia vera.
A hematocrit test measures the proportion of red blood cells in the blood. A deficiency in RBCs is associated with a number of conditions, including anemia, vitamin or mineral deficiencies, and blood loss. A higher than normal hematocrit ratio is manifest in patients with dehydration, polycythemia vera, and heart and lung diseases.
Several handheld and benchtop analyzers are available for POC professional hematology procedures. Producers of these products include Beckman Coulter, Diatron, GlysBy Diagnostics, HemoCue (Radiometer/Danaher), Horiba, Roche, and Sysmex.
Bruce Carlson is the publisher of Kalorama Information, part of Science and Medicine Group.
Disclosure: LabPulse.com is a sister company of Kalorama Information.