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Blood Tests 101 Part 1: Haematology, Metabolic & Liver Tests
Testing your blood can be an informative way to learn about what's going on inside your body. This can help with diagnostics, but it can also provide insight
into the way in which your lifestyle is impacting your health. In this article, I am going to share with you some of the basics of blood tests, but with a particular focus on some case examples to show you how this information can be applied. Earlier this week, we discussed some of the nuances of 'special exceptions' for fit people, and this spurred further interest in this topic among our followers. You can check out that post here. Part 1 will cover 3 of the most common blood tests your doctor will carry out. We will then follow-up next week with some more advanced tests that may be of interest. Stay tuned!
Haematology - Complete Blood Count (CBC)
This test provides information about the blood cells involved in oxygen delivery, immunity, and more. These include red blood cells, white blood cells, and
platelets. This can be informative as to one's overall nutritional status (e.g. malnutrition may produce certain anaemias, such as iron, folate, or B12 deficiencies), along with ongoing infection (e.g. elevated white blood cells that are fighting pathogens), hypoxia (e.g. increased red blood cells following altitude exposure or in the presence of lung disease), and more. Case Example: 25-year-old female presents with symptoms of low energy. She also notes heavy menstrual bleeding. Her CBC demonstrates low haemoglobin (anaemia), with a pattern that suggests iron-deficiency (hypochromic - red blood
cells look pale, hypocytic - cells also look small). This would support her heavy menstrual bleeding as a potential cause of her symptoms, by leading to iron-deficiency anaemia. Further testing such as iron studies could add more information. We discussed another case of iron-deficiency in a recent Triage client case
study.
Biochemistry - Basic Metabolic Tests/Panel (BMP, or U&Es in
Ireland)
The BMP evaluates kidney function and electrolytes primarily, along with glucose and sometimes lactate depending on the context. It includes glucose, calcium,
sodium, potassium, and renal/kidney function markers like blood urea nitrogen (BUN) and creatinine. This can provide information about the body's fluid status (e.g. dehydration or over-hydration could
produce low blood sodium levels - hyponatraemia), kidney function (e.g. creatinine will rise in the blood if not cleared by the kidneys), and more. These tests can get very complex to interpret, and vary widely in different states of illness. Case Example: A 35-year-old powerlifter shows up to his doctor for a routine check-up, having worked out that morning. To his surprise, his creatinine is elevated, and the doctor is worried about damage to his kidneys. In this case, as discussed in our fitness-specific post, his elevated creatinine may just be the result of his training habits, muscle mass, high protein diet, and creatine supplementation (rather than pathology). Of course, other causes should be excluded nonetheless.
Biochemistry - Liver Function Tests (LFTs) & Liver Enzymes
LFTs measure enzymes and proteins produced by the liver. During my medical education, it was drilled into me by a gastroenterologist that LFTs and Liver
Enzymes should be thought of differently. Liver enzymes (e.g. ALT & AST) are not function tests, they merely indicate injury or inflammation to the liver, rather than its function. The true LFTs include albumin, bilirubin, and markers of blood clotting function (e.g. PTT, INR). Beyond the scope of this post really, but an important one for the medical students among you. These tests can provide information that is actually more important than you might think, such as liver disease (e.g. fatty liver), injury from drugs or supplements (e.g. steroids, alcohol, contaminated supplements), and even nutritional status (e.g. low albumin in malnutrition). Case Example: 40-year-old male with obesity presents to his doctor for a routine check-up. His doctor notes that he has a mild transaminitis (elevated ALT & AST), and the man is shocked.
He doesn't even drink alcohol, how could he have injured his liver?! It turns out that this is the result of fatty liver, which has accumulated as a result of his excess body fat, overconsumption, lack of exercise, and poor metabolic health (i.e. non-alcoholic or metabolic-associated fatty liver disease).
Next week, I will follow-up with more blood tests, including hormonal & lipid profiles, which I know you're going to be interested in. Stay tuned!
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