Regularly reviewing blood test results becomes part of your routine when you or a family member are on dialysis for stage 5 chronic kidney disease. While your nephrologist will be regularly monitoring your test results and making decisions and recommendations based on these results, it is very important that you keep on top of your own blood test results so that you can make course corrections as quickly as possible with your diet for example.
A basic test that you have probably heard of before is the CBC Test. While there are many different types of blood tests, the CBC is the most routinely performed and as a dialysis patient you will have this done at minimum once a month and if you have additional health issues maybe more times as different physicians will order various tests, which is why it is good to have a basic understanding of how to read and understand a blood test laboratory report.
What is a CBC test and what does it measure?
CBC stands for Complete Blood Count
A CBC blood test measures the size, number, and maturity of the different blood cells in a specific volume of blood.
Three basic types of cells in the blood are measured, with multiple tests for each giving information that can help your physician get an overall picture of your health:
1. Red blood cells (RBCs) carry oxygen throughout the body. Example tests below:
RBC count – the actual number of RBCs in your blood sample.
Hemoglobin – total amount of this oxygen carrying protein in your blood; measures the oxygen carrying capacity of the red blood cells, this is extremely important for dialysis patients to monitor.
Hematocrit - measures the percentage of red blood cells in the total blood volume.
MCV, MCH, MCHC, RDW - these tests measure the physical features of the RBCs and can give physicians additional information for diagnosis.
Reticulocyte count – measures absolute count or percentage of newly released young red blood cells in your blood sample.
2. White blood cells (WBCs) help your body fight infection.
WBC count - the actual number of WBCs in your blood sample.
Increased numbers of WBCs may indicate the presence of an infection.
Decreased levels of WBCs may indicate certain rheumatic diseases, cancer or reaction to medication for example.
WBC differential - evaluates the 5 different types of WBCs (neutrophils, lymphocytes, monocytes, eosinophils, and basophils).
3. Platelets - help your blood clot and control bleeding.
Total number of platelets in your blood.
MPV (mean platelet volume) – measurement of the size of platelets.
Platelet distribution width – how uniform platelets are in terms of size.
Looking at Lab Test Results
A typical Blood Test Laboratory Report will include 4 columns of data with the following titles from left to right in each column:
Test Name, In Range, Out of Range, and Reference Range. Your results will show under the appropriate column. The “Reference Range” is typically for a person who is not on dialysis due to chronic kidney disease, this is why it is important for you to understand the appropriate ranges for the key blood test results that you monitor regularly and not assume that the in/out of range determinations are correct- your nephrologist can provide you with the appropriate ranges for key blood test results you are monitoring.
Note that some dialysis centers that are run by larger corporations such as Davita will provide their own report that looks very different and includes the meaning behind each result in the context of a person with CKD on dialysis.
As you start relying on your blood test results as an indicator of your overall health, you might start to notice a variance in key blood test results that you monitor regularly when results are received from a different laboratory than your home dialysis center.
Why would you go to a different laboratory? – if you have additional chronic conditions or short term health events that require you to see a doctor outside of your nephrologist, or if you travel and get a lab test report from a different laboratory out of state.
Things to consider when looking at blood test results from different laboratories:
o Normal versus Abnormal Results: The laboratory results from a different laboratory might look a little different in how it is set up and the normal (in range) and abnormal (out of range) values might be slightly different – again these ranges for key tests are not necessarily the correct target ranges for a chronic kidney disease individual on dialysis, so always consult with your nephrologist to know what the appropriate range is for the key test results you are monitoring.
o Reasons why test result ranges are not always absolute indicators of a problem.
Blood Tests can be run on a variety of different instruments/chemical analyzers from a multitude of companies. Each one can provide slightly different results, although the variances between different manufacturers and laboratories should be small sometimes they aren't, and that is why it is good to keep this in mind as you use different laboratories. Differences in results you see could be due to this.
Each person might have their own “normal” range that is an outlier to the majority of individuals - so it is important to watch the trends in your blood test results.
You see a Big change in your blood test result from one test date to another.
Ask for a repeat of a test that is being run, if the discrepancy is seen in a laboratory that is not your regular dialysis center laboratory, ask for it to be repeated at your dialysis center laboratory where majority of your tests have been run so you can compare and look at any trends.
For those extremely curious, you can also ask for the name of the system the laboratory uses and keep this in mind as you move between different laboratories or when traveling.
Pay very close attention to your key blood test results over time. It is important to know the trends for you and keep in mind differences between labs. Don’t make any major decisions based on blips between blood test results. Consult your nephrologist and internist directly if they haven’t already reached out to you.
Making the appropriate changes quickly whether through diet or medical intervention as needed by your nephrologist can make an important difference in terms of how you feel, some course corrections can take time before you will feel and see a change in results and you don’t want to spend longer than necessary not feeling well if you can help it!
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