How to know exactly what your patient's biochemistry results mean
Have you ever run your patient’s bloods, taken a look at their results, and felt like you don’t know enough about what all those parameters mean?
There are a ton of different biochemical tests (literally hundreds of them!) and, in reality, we only run a small number of these in most of our patients.
Our medical patients probably get the majority of these tests - which is why it’s helpful for us to understand what each parameter tells us.
In this post, I’m going to share a full set of biochemistry results with you and break down exactly what each result means - so you can begin interpreting your tests more easily!
Why is this important? Because it’s going to help us:
Plan and develop better nursing care
Prepare for patient deterioration, and
Collect better quality samples, in turn getting more accurate results!
The result? We use more of our skills, have a better understanding of our patients and their diseases, and our patients get better care.
PS. Do you want to know even more about interpreting biochemistry results? I’m hosting a workshop on February 8th showing you what every common result means.
I’ll also be sharing the reasons for abnormal results, and how they impact our patients.
And finally, we’ll work through some results together, to get you interpreting those results confidently!
If you want to join us, make sure you’re a member of the Medical Nursing Academy when doors open on February 1st. The academy includes workshop access (and recordings of every other workshop we’ve ever done!), Q&A calls, book clubs, a community forum and much more.
Get on the waitlist below to be notified as soon as academy doors open!
Let’s look at some results…
We can broadly break down our set of biochemistry results into several categories:
Energy metabolism parameters, including products of carbohydrate and lipid metabolism in the body
Renal parameters, including urea and creatinine
Proteins, including albumin and globulin
Liver parameters, including ALP, AST, ALT, GGT and bilirubin
Pancreatic enzymes, including amylase and lipase
Electrolytes and minerals, including sodium, potassium, chloride, calcium and phosphate.
Energy metabolism
Biochemical parameters that tell us about energy metabolism include glucose, fructosamine, triglycerides and cholesterol.
Glucose and fructosamine are products of carbohydrate metabolism. Glucose is the main cellular energy source, broken down from carbohydrates by insulin. Fructosamine is a glycated protein (a protein formed from glucose) - that represents the mean blood glucose concentration for the protein’s lifespan (approximately 2 weeks).
Lipids are used as alternative energy sources when there isn’t enough available glucose. The main two parameters we measure are cholesterol and triglycerides, which are both synthesised in the liver.
Ketones also provide us with a measure of lipid metabolism. This is because fatty acids are converted into ketones and triglycerides in the liver. We classically think of this in our diabetic patients, as they cannot use glucose for energy. Because they lack the insulin needed to do this, the body converts fats into triglycerides and ketones to be used instead.
Renal parameters
The two major parameters that we use to measure renal function are urea and creatinine. Both are metabolic waste products excreted via the urine, so increased levels give us a good indication of renal dysfunction.
Creatinine is a more sensitive marker of renal function (specifically glomerular filtration rate), since urea can be affected by many other factors. For example, urea can be increased by gastrointestinal haemorrhage or dehydration/hypovolaemia, and reduced in cases of liver dysfunction - whereas creatinine tells us more specifically about the kidneys.
Azotaemia is the term for an increase in creatinine levels. It is only detectable on biochemistry once over 75% of renal function has been lost - SDMA is an earlier indicator of renal dysfunction, increasing when a minimum of 25% of renal function is lost.
There are several types of azotaemia, which can be separated into:
Pre-renal azotaemia (where the cause is before the kidney itself)
Intrinsic renal azotaemia (where the damage/injury has occurred at the level of the kidney), or
Post-renal azotaemia (where the damage has occurred lower in the urinary tract).
Proteins
The two main proteins measured on our biochemistry results are albumin and total protein. Total globulin levels are then calculated from total protein using the formula below:
Total protein - albumin = globulin
Albumin is the most abundant plasma protein, and is synthesised in the liver. It functions as a carrier protein in the transport of materials and drugs, and maintains colloidal oncotic pressure - i.e. keeping our plasma volume normal.
There are actually many different globulins in the body, not just one as our biochemistry results suggest! Our analysers only record total globulin levels.
These different globulins can be divided into 3 main categories:
Alpha globulins
Beta globulins, and
Gamma globulins
They include immunoglobulins (which are involved in antigen binding) and acute phase proteins (which respond to inflammation).
Liver parameters
There are a variety of liver parameters, including ALT, AST, ALP, GGT and bilirubin. Broadly speaking, we can divide them into 3 categories:
Hepatocellular enzymes
Cholestatic enzymes, and
Tests of hepatic dysfunction
Hepatocellular parameters include ALT and AST; these parameters increase in response to hepatocellular injury.
Cholestatic enzymes increase in response to decreases in the flow of bile, or increases in inducible enzymes. ALP and GGT are examples of cholestatic enzymes.
Not all liver parameters indicate liver dysfunction or failure. There can be an acute injury to the liver cells, for example, but the liver is still able to synthesise proteins and eliminate waste products from the bloodstream. There are specific biochemical parameters that tell us about liver function, including urea, ammonia, albumin, bile acids and bilirubin - along with glucose.
Pancreatic enzymes
Lipase and amylase can be used as imperfect measures of pancreatic injury.
We used to use these in the investigation of pancreatitis cases, however, they have largely now been replaced with more specific tests such as pancreatic-specific lipase (spec PLi) activity.
Electrolytes and minerals
The three main electrolytes we measure on our biochemistry results are sodium, potassium and chloride. These substances are vital for many different body processes, including:
Cell, nerve and muscle function
Fluid balance
Blood pressure maintenance
And many more.
Most changes to electrolyte levels occur due to:
Changes in body water content/balance
Changes in electrolyte intake (e.g. anorexia causing hypokalaemia)
Movement of electrolytes between intracellular and extracellular fluid
Loss or excretion of electrolytes (e.g. an increase in urinary sodium loss in Addisonian patients)
Calcium and phosphate are two vitally important minerals, that exist in a carefully-controlled balance.
The levels of calcium and phosphate are regulated carefully across the bone, kidneys and GI tract to maintain normal circulating levels.
Calcium exists in:
An ionised (freely-circulating) form,
A protein-bound form, and
A complexed form, bound to other ions such as bicarbonate and phosphate.
Biochemistry analysers read the total calcium content. However, ionised calcium is the most accurate form of calcium measurement available. This is measured on most blood gas analysers, or can be submitted to an external laboratory if you don’t have access to blood gases in practice.
Phosphate is the most abundant intracellular anion (negatively-charged ion). It is mostly present in bone, but smaller amounts are present in muscle and extracellular fluid. Less than 1% of all phosphate in the body exists in the bloodstream.
Phosphate is the term given to oxygen-bound phosphorus. Phosphorus itself is unstable, so only exists within the body in its oxygen-bound form. There are two types of phosphate in the body: organic and inorganic phosphate.
Inorganic phosphate or IP is what our biochemistry analysers actually measyre. This form is circulating either freely in the bloodstream, or bound to hydrogen ions.
Organic phosphate is bound to carbon-containing molecules. Examples include:
ATP (adenosine triphosphate) - the major cellular energy source, produced from glucose and oxygen, and
Phospholipids - which form part of the cell membrane, and allow substances to move in and out of cells.
So that’s an overview of the most common biochemical parameters we see! By understanding the function of each of them, and what they tell us about our patient, we can adjust our treatment and nursing care, monitoring for complications or signs of deterioration.
Do you get to discuss blood results in your hospital? Would you like to? DM me on Instagram and let me know!
Want more information on what these results mean for our patients, and how that impacts our nursing care?
Don’t forget to join us for the Biochemistry 101: How to Interpret Blood Results workshop on February 8th! Give me 90 minutes of your time, and in a relaxed, information environment we’ll go through:
What the common results mean for our patients, and reasons for abnormal results
Results from real patients, so that we can practise interpreting their results together, and looking at how this impacts their nursing care!
You’ll also get a recording of the session (so no worries if you can’t make it live), a workbook, and a CPD certificate for attending.
You can get access to the workshop, plus a ton of other perks as a Medical Nursing Academy member - doors open on February 1st, and you can be the first to get in by signing up to the waitlist below!
References
Cornell University College of Veterinary Medicine. 2020. EClinPath. [Online] Available from: https://eclinpath.com/chemistry/
Sirois, M. 2020. Laboratory Procedures for Veterinary Technicians. 7th Ed. Missouri: Elsevier.
