A History of Bloodwork: Part II
- V. A. Cyr
- Oct 2, 2024
- 6 min read
In A History of Bloodwork: Part I, we touched on the origins of testing blood and bloodletting. In Part II, we will delve further into the uses of bloodwork as a diagnostic tool. Why do we test blood? What can be tested in the blood? What do all of those coloured vials mean?
Uses in Medicine
Bloodwork Specimens
The vials that are used to collect the blood are colour-coded and have different preserving agents in them for different tests.
Bottle-shaped containers are used to test for blood cultures. This is done with two bottles every time to test for aerobic (blue cap) and anaerobic (purple cap) bacteria in the blood. These are important to do if a patient presents with signs of infection (e.g., fever) and they need specific antibiotic therapy as treatment.
An example of blood culture bottles (Kurin, n.d.). A marker is used to indicate how much blood must be taken (usually about 10mL above the agent in the bottle) in order to complete the testing accurately.
Light blue is used to test for coagulation, d-dimer (diagnostic of a “heart attack”), and thrombophilia (bleeding disorder).
Red is used in serology to test for viral, bacterial, and fungal infections.
Yellow tests for urea, electrolytes, liver function, thyroid function, lipids (fats), and immunology.
Green is used for routine biochemistry (measures concentrations of chemicals in the blood).
Purple is the most common as it is used to test the complete blood count.
Pink is used for type and crossmatching testing.
Dark blue tests for trace elements in the blood.
Grey is used to test blood glucose and lactate levels.
An example of some blood sample containers (K. S. Medical n.d.).
Type and Crossmatching Test
In Part I, we described the type and crossmatched with the ABO types of blood and the importance of giving someone the correct blood type.
Blood Transfusions
A blood transfusion is given to a patient who has lost a large amount of blood. This can be caused by procedures (e.g. surgery), trauma (e.g., wound), or disorders (e.g., anemia). As mentioned before, the type of blood given to the patient (donor) should match their own (recipient). If that cannot be done, any patient can receive O- blood in the case of an emergency. Blood can be donated by healthy individuals, cleaned, and given back to those in need. Various types of blood products can be given during a transfusion.
Whole blood contains all components: RBCs, WBCs, platelets, and plasma. This would be tranfused to increase total blood volume in those with hypovolemic shock
Packed RBCs are when the red blood cells have been separated from the plasma and platelets. This is usually given in patients with low hemoglobin.
Platelets can also be separated from the other blood components and given independently. These are given to patients with clotting deficiencies (e.g., thrombocytopenia).
Fresh frozen plasma (plasma without any blood cells present) contains cryoprecipitate and fibrinogen, which help develop more clotting factors and increase intravascular volume.
Here is an example of a modern blood transfusion setup (National Cancer Institute, 2015).
A Brief History of Blood Transfusions
The first recorded successful blood transfusion was done on a dog from another dog’s blood in 1665 (American Red Cross, 2024). In 1667, the first transfusion was done on a human, receiving sheep’s blood (American Red Cross, 2024). In 1818, the first transfusion of human blood to another human was done after a severe postpartum hemorrhage (bleeding after giving birth) (American Red Cross, 2024). In the 1940s, the USA began a national blood collection program, which was used to treat the wounded during World War II (American Red Cross, 2024). The first testing of donated blood for Hepatitis B began in 1971. In the 1980s, the law required testing donated blood for the Human Immunodeficiency Virus (HIV) (American Red Cross, 2024).
Here is a blood transfusion apparatus, circa 1917-1918 (Science Museum Group, n.d.).
Organ Transplants
Just as type and crossmatch are vital in blood transfusions; it is also essential to ensure the donor matches the recipient in organ transplant cases. Both must have matching blood types to improve the chances of success of the transplant. Although a person will be on anti-rejection drugs to help the body accept the new organ, it can sometimes reject it anyway. Matching the blood types is critical to reduce the risk of side effects such as rejection and hemolysis (see Part I). Organ donation can save someone’s life! You can check out more information on organ donation and become a donor here: Canada.ca.
Here are some organs that can be transplanted between humans (HealthDirect, 2024).
Laboratory Blood Tests
Below is a brief overview of common tests that can be performed using blood (this is by no means an exhaustive list). Along with the CBC, blood can be tested for electrolytes, glucose, lipoproteins, liver function, etc. A short list of diagnostic testing for various disorders is also discussed below.
Complete Blood Count (CBC)
Red Blood Cell (RBC) count is the amount of RBCs found in the blood.
Hemoglobin (Hgb) is a protein in the RBCs that binds to oxygen and brings it around the body. A high Hgb value can be seen in dehydration, and low Hgb can result from various clinical problems (e.g., anemias).
Hematocrit (Hct) is the amount of packed RBCs found in 100mL of blood or the concentration of RBCs in the blood. Low Hct is seen in anemias and leukemias, while elevated levels are found in dehydration.
RBC Indices
Mean Corpuscular Volume (MCV) is the size of the RBC. They can be microcytic (small), normocytic (normal), or macrocytic (large).
Mean Corpuscular Hemoglobin (MCH) is the weight of hemoglobin in the RBC. This value is elevated in macrocytic anemias and decreased in hypochromic anemia.
Mean Corpuscular Hemoglobin Concentration (MCHC) indicates the hemoglobin concentration per unit volume of RBC. A decreased MCHC can indicate hypochromic anemia.
RBC Distribution Width (RDW) is the size difference between RBCs. An elevated RDW can be a predictor for iron deficiency anemias.
The normal ranges of RBCs and Indices for men and women (Cloyd, 2024).
White Blood Cell count is the amount of WBCs found in the blood. WBC Differentials testing includes the number of neutrophils, eosinophils, basophils, lymphocytes, and monocytes. All of these should not be present (or be in very low amounts) in the blood unless the patient is actively fighting an infection.
The normal ranges of WBCs and Differentials for men and women (Cloyd, 2024).
Platelet count is the amount of platelets found in the blood. A low platelet level can indicate a bleeding disorder (e.g., hemophilia), while a high level can indicate hypercoagulability and a higher risk of clotting.
Diagnostic Testing
HIV is a virus that causes Acquired Immunodeficiency Syndrome (AIDS). The CD4+T lymphocyte possesses the receptor site for HIV. This is diagnostic testing to determine if the person is negative for antibodies. Now, there is also a test to determine the CD4 count to see if the person is at risk of transmitting HIV to someone else.
Genetic testing for cancers can be done with a blood specimen. The BRCA gene mutation causes cancers in the breast and ovaries. Since this is a genetic test, it is recommended that those with a family history of cancer be tested for it.
Sexually Transmitted Infections (STIs) such as Syphilis, Herpes, and Human Papillomavirus (HPV) can all be tested for using blood. Antibody testing can also determine if someone has been vaccinated for HPV, for example.
Drug testing is also commonly done in the hospital. This can be to determine illicit drug use (e.g., heroin), overdoses (e.g., acetaminophen), and to determine if the medication is within therapeutic levels (e.g., vancomycin).
This post just scratches the surface for what can be done with blood testing. To think that all of this came from bloodletting and leeching! What is the most interesting fact about bloodwork that you learned?
– V. A. Cyr
References
American Red Cross. (2024). History of Blood Transfusions. Red Cross Blood Services. https://www.redcrossblood.org/donate-blood/blood-donation-process/what-happens-to-donated-blood/blood-transfusions/history-blood-transfusion.html
Cloyd, J. (2024). Red Blood Cell (RBC) Components [Image]. Rupa Health. https://www.rupahealth.com/post/how-to-interpret-cbc-results-a-comprehensive-guide
Cloyd, J. (2024). White Blood Cell (WBC) Components [Image]. Rupa Health. https://www.rupahealth.com/post/how-to-interpret-cbc-results-a-comprehensive-guideHealthDirect. (2024). Organ transplants [Image]. https://www.healthdirect.gov.au/organ-transplants
K. S. Medical. (n.d.). 7 Factors Affect The Prices Of Blood Collection Tubes [Image]. https://ksmedical.com/blood-collection-tubes-price/
Kee, J. L. (2018). Laboratory and Diagnostic Tests (10th ed.). Pearson.
Kurin. (n.d.). Blood Culture Collection FAQs [Image]. https://www.kurin.com/blood-culture-collection-faqs/
National Cancer Institute. (2015). Blood transfusion [Image]. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/blood-transfusion
Pulse Notes. (2022). Blood bottles . https://app.pulsenotes.com/clinical/pathology/notes/blood-bottles
Roberts, M., Yancey, R., Montague, J. & Richard, A. (2024). Blood Products: Nusring pharmacology [Video]. Osmosis by Elsevier. https://www.osmosis.org/learn/Blood_products:_Nursing_Pharmacology
Science Museum Group. (n.d.). Blood transfusion apparatus believed to be designed by Oswald Hope Robertson [Image]. https://collection.sciencemuseumgroup.org.uk/objects/co140870/blood-transfusion-apparatus-blood-transfusion-apparatus?_gl=1*5bw6gj*_gcl_au*MTI2Njg5MDQ4Ny4xNzI3OTEyODky
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