What test that can be done in one minute, can be used for acute diagnosis, health screening, patient follow-up or health maintenance, and offers at least 16 different elements of information? Urinalysis could be a silver medal podium finish, but the gold goes to CBC — the complete blood count!
How well-recognized is the CBC as a critical hematology test? In terms of testing frequency in the United States, CBC with automated differential (CPT code 85025) is the number one most commonly performed test, ahead of thyroid stimulating hormone and comprehensive metabolic panel1. In 2014, 41.5 million CBC tests were performed in the US1. That’s one test for every 8 US citizens!
One reason for the CBC test’s popularity is its consistency and ease of use. The modern hematology instrument is a marvel of invention, whether in 3-part or 5-part differential configuration. It is simple to use and consistent among laboratory diagnostic equipment.
Though it might appear obvious, a discussion of blood’s role in health and disease is essential to understanding the value of the CBC. Let’s look a bit deeper to think about blood’s role in health and disease. Blood is a remarkable tissue.
First of all, blood helps make up the body’s most abundant tissue in the human body2. The average person’s blood weighs more than any single organ in their body. Blood is estimated to account for about 7% of the weight of the average person, or about 10.5 lbs for a 150 lb individual3. At the same time, blood is the only tissue that comes in contact with every organ of the human body. Blood is the master transporter and communicator of the human body, delivering oxygen, hormones and nutrients to the tissues and removing CO2 and other waste products. When an infection occurs, white blood cells (WBCs) marshal the immune system and lead the fight against the infection. WBCs are the first line of defense for the human immune system and can fight anywhere in the body.
In health, blood is the key. In disease or injury, it is often the first place to look for diagnostic information. Among its remarkable attributes are the cells that comprise blood: red cells, white cells and platelets renew themselves about every 60 days4. Ask any elite athlete about conditioning. They will tell you that successful conditioning relies upon the ability to find ways to transport oxygen more efficiently to increase performance and stamina.
While a CBC does require drawing blood either by a venous draw or capillary collection, it does not require separation of the blood components by centrifugation. An anti-coagulated blood sample is immediately ready for testing. In many hematology systems, the sample can be drawn by the instrument from an unopened blood collection device automatically, with no exposure of the operator to the sample. Quick, safe, and convenient! Emergency rooms and urgent care centers value the ease of sample acquisition and preparation, as well as the wealth of information delivered by CBC results, not to mention its speed. Results in under one minute make critical decision making faster and more confident.
It is incredible how many differential diagnoses may be derived from CBC results. Anemia, internal bleeding, infection (bacterial or viral), cancer, annual physical exam and general health status are some of the classics. Platelet studies expand its utility in both bleeding disorders and metabolic or treatment status evaluation involving chemotherapy.
| Tested Parameter | Full Name | Typical Disease States Tested For |
| WBC | White blood cell count | Viral infection, bacterial infection, inflammation due to injury/allergies/disease, cancer (i.e. Leukemia) |
| RBC | Red blood cell count | Anemia, polycythemia, porphyria |
| HGB | Hemoglobin | |
| HCT | Hemocrit | |
| PLT | Platelets | Clotting disorders; whether to perform chemotherapy |
| MCV | Mean corpuscular volume | Anemia |
| MCH | Mean corpuscular hemoglobin | Anemia, bleeding disorders |
| MCHC | Mean corpuscular hemoglobin concentration | Anemia |
| RDW-SD* | Red cell distribution width (standard deviation) | Helps to differentiate between thalassemia and iron deficiency anemia |
| RDW-CV** | Red cell distribution (coefficient of variation) | Helps to differentiate between thalassemia and iron deficiency anemia |
| MPV | Mean platelet volume | Anemia, inflammatory bowel disease, myeloproliferative diseases (polycythemia, others) |
| 5-Part Differential Parameters*** | ||
| NEUT% | Neutrophil % | Bacterial or fungal infection |
| LYMPH% | Lymphocyte % | Viral infection or indicator of cancer cells |
| MONO% | Monocyte % | Infection (phagocytes “memory cells”, remind the immune system how to destroy it |
| BASO% | Basophil % | Inflammation, asthma |
| EOS% | Eosinophil % | Allergy, parasitic infection, indicates issues within the spleen, collagen of the body, and central nervous system |
| NEUT% | Neutrophil % | Infection |
| LYMPH# | Lymphocyte % | Infection |
| MONO# | Monocyte % | Infection (phagocytes “memory cells”, remind the immune system how to destroy it |
| BASO# | Basophil # | Inflammation, asthma |
| EOS# | Eosinophil # | Allergy, parasitic infection, indicates issues within the spleen, collagen of the body, and central nervous system |
For diagnosis of acute conditions including internal bleeding or an infection spiraling out of control, every second counts. The CBC test shines here, using anti-coagulated whole blood, the ability to use a closed collection device without centrifugation, in analytical time in the range of one minute. From patient presentation to result availability, the CBC test sets an enviable standard for speed: 16+ tests available in under 5 minutes. No wonder it is the number one most utilized lab test in the US1. The CBC with automated differential is the sprint star of urgent care, emergency care and clinical lab every day.
The choice to use the CBC with automated differential is predicated on two primary factors:
In many primary care settings, basic hemoglobin and hematocrit tests may be performed on simple waived systems from Hemocue and others. Adding a white blood cell test to look for an infection is useful, but takes the license requirement to moderate complexity. An increasing number of urgent care and free-standing emergency room centers are investing in providing hematology systems and the required CLIA license to provide the information they need to expand diagnostic utility beyond the basics. They can then assess anemia and potential infections with a larger suite of information. A CBC test with 3-part differential provides a suitable system for some practices. A 5-part system may well be the right choice for any practice that requires a detailed view of all 5 types of WBC for their diagnostic process, such as oncology or rheumatology practices.
Deciding on the best path forward starts with consideration of your patient population, the diseases you see and manage frequently, and the level of care your practice provides. This is certainly a decision that requires careful thought and consensus across the practice.
Once you have established your specific testing needs and understand how a hematology test can improve them, it’s time to call in the experts. Many practices rely on the advice of their colleagues, as well as the lab of the hospital where they typically practice, for product and lab advice. In addition, your distributor can bring hematology suppliers to meet with you for detailed discussions in understand your patients’ needs and your desire for sufficient diagnostic information to manage them effectively. Some distributors also offer CLIA consulting assistance to practices looking to make the change from CLIA certificate of waiver to CLIA moderate complexity testing, like hematology.
No matter how you make your decision regarding hematology testing, you will be selecting a pathway to fast, effective lab results that can assist you in patient management from acute needs for anemia and infection to annual physicals and assessment of a variety other conditions. Where does CBC testing fit? It fits in more patient settings than any other single test.
*Measured
**Calculated
***3-part differential systems typically report:
1: https://oig.hhs.gov/oei/reports/oei-09-15-00210.pdf
2: http://www.biologyreference.com/Ce-Co/Connective-Tissue.html
3: https://wonderopolis.org/wonder/how-much-blood-is-in-your-body
