After kidney transplantation, blood work is done regularly. Does your doctor throw around words like erythrocytes and thrombocytes? Here you will find some of the most important values explained for "normal" people without a medical degree!
What values are used to measure kidney function?
The most important parameter after transplantation is usually your kidney function. It is determined by a series of laboratory values such as creatinine, urea or the estimated glomerular filtration rate (=eGFR). What exactly lies behind these values, you will learn in the following paragraphs.
1. Creatinine
Creatinine is a breakdown product from muscle metabolism. It is excreted via your kidneys. If your new kidney does not function as it should, the creatinine level in your blood will increase. Of course, your exact creatinine level also depends on your muscle mass. So your creatinine value tells you how well your kidney can filter the harmful substances out of your blood.
Target levels for your creatinine depend on your sex at birth. For healthy women, the target level is between 0.5 and 0.9 mg/dL. For healthy men, the target level is between 0.7 and 1.2 mg/dL. But don't worry if your levels are slightly elevated after transplant. This is not uncommon. After transplant, your medical team wants to especially avoid large fluctuations or increases in creatinine levels. The goal is a level that is not too high and remains stable over time.
2. Urea, urea-N (=BUN)
Similar to creatinine, urea is a breakdown product. It comes from your protein metabolism and is mostly excreted through your urine. A high urea value therefore also indicates a lower excretion rate via your kidneys and thus a decrease in kidney function. Depending on the laboratory, either urea or the nitrogen contained in urea (= urea-N) is measured. The target values are then different but the meaning is the same.
The target values for urea-N (also called BUN) in healthy people are between 6 and 20 mg/dL or 2.1 and 8.9 mmol/L. The target values for urea lie between 13 and 54 mg/dl. Sometimes mmol/L are used as units for urea and in this case, the reference range is 2.1 - 8.9 mmol/L. After transplantation, this value may also be slightly higher than normal.
3. Cystatin C
Cystatin C is a protein in your blood. In a healthy state, it is filtered out of your blood by your kidneys and broken down there. Your kidneys keep the cystatin C level in your blood in balance. If the filtering function of your kidneys decreases, the cystatin C value increases - very similar to creatinine. Therefore, cystatin C is also considered an indicator (=a so-called "marker" or simply value) that can be used to determine the filtering function of your new kidney.
The target values for cystatin C are between 0.61 and 0.95 mg/l for healthy people, regardless of biological sex. Again, the values may well be somewhat higher after transplantation.
4. Estimated glomerular filtration rate (=eGFR)
The estimated glomerular filtration rate provides information about how much blood your kidney filters per minute. It is not a separate value, but is calculated. The creatinine or cystatin C value, among others, are needed for the calculation. In the Mizu app, you can enter your eGFR directly.
The eGFR value can classify chronic kidney insufficiency into five different stages. As the function of the kidneys decreases, the eGFR also decreases from stage 1 to stage 5. If the eGFR is below the value of 15 mL/min (=stage 5), this is indicative of kidney failure. Even after transplantation, the eGFR is still used to monitor how well your new kidney is working.
After transplantation, your eGFR does not necessarily have to be above 90 mL/min again. In fact, only a few people reach this value after transplantation. It is more important that your eGFR is not significantly reduced and - as with the other values - reaches a stable level. In general, after transplantation, the trend of many values is more important than the exact value on a specific date.
Albumin-Creatinine Ratio (=ACR)
Simply put, the ACR describes the ratio of albumin to creatinine in your urine. Creatinine, as you already know, is a breakdown product from your muscle metabolism that is often used to measure your kidney function. Albumin is one of the most important proteins in your body and is present in large quantities in the plasma of your blood (=plasma protein) in a healthy state. Here it serves as an important transporter for hormones, fats or drugs.
If albumin is present in larger quantities than usual in your urine (=albuminuria), this may indicate damage to your transplanted kidney. Therefore, the ACR is one of the most important laboratory values for your medical team to check your kidney function even after the transplantation. In general, a distinction is made in albuminuria between so-called microalbuminuria (=little albumin in the urine) and macroalbuminuria (=much albumin in the urine). The crucial difference in this case is the amount of albumin that can be measured in your urine. In the following table we have summarized the different reference values for you. As always, you can get more information from your medical team.
In addition to the ACR, the protein-creatinine ratio (UPCR) in urine can also be determined. Unlike the ASC, this does not determine the ratio between albumin and creatinine, but rather the ratio between the total amount of protein and creatine in the urine. The UPCR is usually higher than the ACR, since in this case all the proteins in your urine are added together. Low levels of UPCR indicate normal kidney function, while elevated levels may indicate damage to your transplant. Significantly elevated UPCR values may also indicate a more rapid progression of possible functional impairment of your transplanted kidney. Classic reference values for UPCR are:
Immunosuppressants
This group of drugs slows down (=suppresses) your defense system (=immune system) and protects your new kidney from being rejected by your immune system. They are an integral part of the permanent therapy after an organ transplant - regardless of which organ was transplanted.
What is the "level" of your immunosuppressants?
As always in life, immunosuppressants can be viewed from different perspectives. For example, their goal is to protect your new kidney from attacks by your immune system. At the same time, however, they can also cause undesirable side effects. To achieve the optimal balance between the desired effect and undesired side effects, the concentration (=level) of your immunosuppressants in your blood is determined regularly. As always, the exact target value for the amount of immunosuppressants in your blood can be obtained from your treating nephrologist.
What is the approximate target level for tacrolimus?
A commonly used immunosuppressant after kidney transplantation is tacrolimus. An important concept in the dosing of tacrolimus is the so-called trough level. This is the amount of tacrolimus in your blood right before the next dose. Generally, the target trough level is individual for each patient and depends on how long ago the transplant took place. Especially shortly after transplantation, higher levels are often targeted than after a few months. The exact target values for the valley levels of your immunosuppressants are always given to you by your medical team. You can document your Tacrolimus level in your Mizu app at any time to keep track of this important drug level.
Below we have summarized typical target values for your Tacrolimus level, depending on the duration after transplantation. These target levels apply if your kidney is functioning well and you have no other physical or health problems post-transplant. In principle, of course, as always, the values given to you by your medical team take precedence. Possible target values for other immunosuppressants can also be found in other articles of the Mizu App.
How can the immunosuppressant level be influenced?
The level of your immunosuppressants mainly depends on the correct intake of your medication. If you take your medications at the times your medical team tells you to, your levels should be within the prescribed range. However, there are a few additional things to keep in mind.
Grapefruit juice, for example, can delay the breakdown of medications, including your immunosuppressants, and lead to higher levels of the drugs in your blood. St. John's wort tea can speed up the breakdown of medications, leading to lower levels. As you can probably guess, this means that you should stay away from grapefruit and St. John's wort if you are on immunosuppressants because of a transplant. Also, you should always check with your medical team first when taking other medications along with your immunosuppressants. This is because they can affect each other, which is called an interaction. In some circumstances, drug interactions can have health consequences.
CRP
The C-reactive protein (=CRP) is a part of the body's immune system. It is produced by your body during inflammations or infections. The CRP level in the blood therefore also rises during inflammation, tissue damage or infection. However, the CRP level does not allow any conclusion to be drawn about the exact clinical picture, the cause of infection or the origin of tissue damage. It is a nonspecific value that usually requires further investigations to determine the exact cause.
After transplant, infections are more common and more dangerous to your body and your new kidney due to the use of immunosuppressants. Therefore, your medical team will check your CRP level regularly after the transplant.
What is the approximate target value for CRP?
The target value for your CRP is below 5 mg/L in blood. In some cases, the CRP level is also measured in mg/dL. Then a target value of below 0.5 mg/dL applies. The level of CRP can indicate the severity of an infection or inflammation.
How can CRP be influenced?
As you already know, your CRP level increases due to possible inflammation or infection, among other things. After the transplant, you should therefore protect yourself as best you can from potential sources of infection. A healthy, low-bacteria diet, sufficient exercise and enough sleep are suitable for this.
In addition, you will be offered various vaccinations before and after the transplantation in order to be protected, for example, from the flu during flu season.
Leukocytes
Leukocytes are the white blood cells in your body. They are part of your immune system and defend you against infections. Therefore, your white blood cell count usually rises when you have a bacterial infection or inflammation.
What is the approximate target level for leukocytes?
Depending on what unit of measurement the lab gives, it is usually 4-10 x 10^9/L or 4-10 G/L leukocytes.
How can leukocytes be affected by renal therapy?
After transplant, you have a reduced defense against infection. So your body's defense system is not quite as strong. Therefore, it is immensely important to keep yourself fit and to maintain a healthy diet. After your time on dialysis, you should rebalance your diet. However, keep the principle of "low-bacteria nutrition" in mind. This will help you prevent infections and keep your immune cells and thus your leukocytes within the normal range. You can read more about this in the other articles of the Mizu App.
Hemoglobin
Hemoglobin (=Hb) is a protein in your red blood cells, the erythrocytes. Since it gives your red blood cells their red color, it is also called blood pigment. Hemoglobin's most important job is to transport oxygen and carbon dioxide in your blood. A lack of hemoglobin means less oxygen for your cells and can make you tired and weak.
In serious cases it can even lead to shortness of breath. Since hemoglobin is the oxygen and carbon dioxide carrier in the blood, this value is used to detect anemia.
What is the approximate target value for hemoglobin?
While lower target values often apply on dialysis, the target range for your hemoglobin after transplantation is between 13 and 17 g/dL for men and between 12 and 16 g/dL for women. Immediately after transplant, it is often the case that these levels are still somewhat lower and need to settle.
How can hemoglobin be affected by renal therapy?
As with erythrocytes, nutrition plays an immensely important role. Your body needs iron to make hemoglobin. You can also check the iron content of foods in the food checker of your Mizu app.
