The properties of the blood and the ease of its retrieval make it a useful source for doctors to analyze to measure specific features of homeostasis within patients. This allows for accurate diagnosis and treatment options to be prescribed.
How do Blood Tests Work?
Taking blood samples from patients is typically used in order to analyze aspects of the individual’s health. It can allow doctors to diagnose any potential blood-related and non-blood related disorders, as well as monitoring the progress of conditions and effectiveness of treatments.
Several factors can be measured during laboratory analysis of the samples, including complete blood count, hormone and electrolyte levels, types of leukocytes, and levels of blood plasma protein.
To establish the presence or absence of a range of medical conditions, the patient’s blood properties can be analyzed, and comparisons made to a set of healthy or normal values known as ‘reference ranges’.
Blood Test: Apple's Eyes Studio / Shutterstock
Understanding Laboratory Blood Test Results
There is a set category of reference ranges that can be analyzed on a case-by-case basis to investigate patients’ health.
Some of the most common blood test parameters are outlined below, including what it means if your results deviate from the normal value ranges.
White Cell Count (WBC)
The measurement of a patient’s white cell count can enable doctors to predict a range of medical conditions, such as coronary heart disease (CHD). A normal reference range of between 4 and 11(109/L) is expected for both men and women.
Results above this figure may be indicative of inflammation linked to the immune system and experienced in response to exposure to toxic substances such as cigarette smoke, or infection.
In the long term, higher than normal levels of WBC have been associated with an increased likelihood of developing CHD.
Picture of white blood cells, red blood cells and platelets in blood film, analyze by microscope, 400x : Jarun Ontakrai / Shutterstock
Measurement of hemoglobin levels allows the oxygen-carrying capacity of a patient's blood to be gauged. For men, normal results range between 130-180g/L and 115-165g/L for women. If your results are lower than these values, then it may mean you have anemia. This can be caused by lowered red blood cell production, hemolysis (abnormal destruction) of red blood cells, and extreme blood loss.
In contrast, high levels of HB may mean the patient is suffering from extreme levels of dehydration, inherited heart disease, or producing too many red blood cells due to smoking.
Structure of human hemoglobin molecule. Vector diagram. Hemoglobin is the substance in red blood cells that carries oxygen. Image Credit: Designua / Shutterstock
A patient’s lymphocyte count may be taken if they’re a risk or currently have cancer. The analysis of the immune system is important in those with cancer as it holds an integral part in the progression and onset of cancer.
Lymphocytes, in particular, are effector cells that help to protect the body in an immune response and could prevent the progression of several tumors. Normal reference ranges for lymphocyte counts for both men and women is 1.5-4.5 (109/L). Therefore, in patients with cancer, high lymphocyte levels are favourable, whereas low levels could be linked to poor prognosis of certain types of cancer.
Red Blood Count (RBC)
The results from a blood test that analyzes RBC can assist in the diagnosis of a plethora of blood-related conditions. For men, 4.5-6.5 (1012/L) is a normal red blood count result and for women, 3.8-5.8 (1012/L). Similarly to having a low HB count, having a low RBC could be indicative of iron deficiency anaemia in addition to a deficiency of B12, B6, and folate.
High levels of RBC could indicate the presence of a range of health conditions such as hypoxia (low levels of blood oxygen), pulmonary fibrosis, dehydration, and congenital heart disease.
Eosinophils are cells that come from the bone marrow and reside within bodily tissues. They’re involved in a range of processes such as the release of mediators for inflammation, the presentation of antigens, and homeostatic-related immune responses.
Typical blood test values for eosinophils are between 0-0.4 (109/L) in both men and women. Raised levels of eosinophils in a patient’s blood test results may be linked to the onset of eosinophilic diseases.
If you’re analyzing your blood test results, it’s important to note that there’s a degree of consideration that needs to be taken. For example, despite having reference ranges which set out the parameters for normal values, doctors typically have to take into consideration each patient’s personal background. Specifically, they will consider any medication currently being taken by the patient, medical history, and the results of any blood work or other medical investigations.
For example, higher than expected levels of alkaline phosphatase is not only okay but desirable, in some patients. Alkaline phosphatase is a type of enzyme involved in the synthesis of new bone cells. Blood level concentration typically increases in proportion to the production of new bone cells. Therefore, high blood levels of alkaline phosphatase are often considered not to be an issue in growing children and adolescents.
Additionally, it’s important to note that the typical reference ranges may differ. For example, different laboratories use varying types of testing methods and equipment. As a result of this, they may produce their own set of reference ranges. Furthermore, between laboratories across the world, the units of measurements can often vary.
- NHS Trust (2017). Haematology Normal Adult Reference Ranges. https://www.royalwolverhampton.nhs.uk/services/service-directory-a-z/pathology-services/departments/haematology/haematology-normal-adult-reference-ranges/
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- Lab Tests Online UK (2018). Reference Ranges & What They Mean. https://labtestsonline.org.uk/articles/laboratory-test-reference-ranges
- National Heart, Lung, and Blood Institute. Blood Tests.https://www.nhlbi.nih.gov/health-topics/blood-tests