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Understanding Your Labs

By Sarah Biel-Cunningham

June/July 2006

Sarah Biel-Cunningham, M.S.W.
An important part of your HIV health care involves regular doctor's visits for lab work. These laboratory tests are used as a part of your treatment plan to help monitor your HIV progression as well as providing information to help you and your doctor make decisions about your treatment regimen -- whether you should start, stop, or change treatments. A commitment to regularly monitoring your lab work is an important way to take charge of your health, just knowing and understanding this aspect of your health care is crucial for many to find a level of comfort with understanding their HIV.


The Basics

There are several different types of laboratory tests that can be used to monitor HIV. The four common tests are: viral load, CD4 count, complete blood count, and blood chemistry tests. These four tests are blood tests and are the most comprehensive tests available to monitor the health of individuals living with HIV. Depending on your health and whether you are on a treatment regimen, most doctors will run these tests every 3-6 months. Since these tests are used to monitor your overall health through comparison of tests over time, it is important when you are first diagnosed or when you start your first treatment regimen to get your lab work done to provide a baseline for future comparisons.

To read your lab report you will find listed on the summary the names of the tests performed, the results of the tests, and the reference ranges. The results are typically reported as absolute numbers measure per a specified unit or as percentages. These results can then be compared with the provided reference ranges for those particular tests. Reference ranges are the determined averages that a person should fall within to be considered in a "normal" range. The numbers for the reference range are determined by sampling a large population of healthy individuals to determine a range of averages.


Viral Load

This test is responsible for measuring the amount of HIV in your blood (copies/mL). There are two types of viral loads tests: polymerase chain reaction (PCR) or branched DNA (b-DNA). The test results summary will specify which test was used, however, these tests come to a comparable conclusion but the results of the two different tests don't correlate. Even though the results basically provide you with the same information, it is important to use just one of these test over time for more consistent comparisons.

The goal with this test is to reach, or get as close to undetectable as possible. For the PCR viral load test, less than 50 copies of HIV in the blood is considered undetectable, and for the b-DNA viral load test less than 400 copies of HIV in the blood is undetectable. With a viral load test it is recommended that you are tested every three months and it takes approximately 4-7 days for the laboratory to process the test.


CD4 Count

This test measures how many CD4 cells (T-cells) are in your body, reflecting the health of your immune system. The focus of this test is to measure the absolute CD4 count. The absolute CD4 count refers to the number of CD4 cells available in your immune system. CD4 cells are the part of your immune system responsible for fighting infections. These are the cells directly targeted by HIV. As HIV progresses, they take over the CD4 cells using the cells to replicate HIV, killing of the original CD4 cell in the process. This is why a CD4 count is a useful indicator of immune system health. The more CD4 cells the stronger the immune system. On average, individuals living with HIV are encouraged to monitor their CD4 count to make sure it is above 200. If you go below 200, however, it is highly encouraged that you work with your doctor to either start a treatment regimen, or adjust your current drug regimen. With the CD4 count, it is recommended that you test as soon as you test HIV positive, then follow up every 3-6 months. Expect it to take two weeks for the laboratory to process the test.


Complete Blood Count (CBC)

This test is a measure of all the components that make up blood. CBC's are important because some drugs can cause low red or white blood cell counts which can lead to anemia or other blood disorders. This test measures the amount of white blood cells, hemoglobin, hematocrit and platelets. With this test a high white blood cell count can suggest that the body is fighting an infection which may be undetectable, a low red blood cell count with the hemoglobin and hematocrit could be the result of anemia from the HIV medications, and a low platelet count could effect blood clotting. This test is different from the viral load test or the CD4 count because it doesn't directly show a progression related to HIV, but it does help with determining the overall health of the individual. With the CBC, it is recommended that you be tested every three months if you are taking a drug regimen. If you are not on HIV medications then this should be a test included with your annual physical. This test takes 1 day for the laboratory to process.


Chem-Screen

This test is a general screening to measure whether your major organs (heart, liver, kidneys, pancreas), muscles, and bones are working appropriately by measuring specific chemicals in your blood. This test is essential in the detection of infections or side effects from medications. One of the most important focuses of this test is monitoring liver enzymes. The liver is an important organ to help process medications, and with these medications demanding more from your liver, there is a potential for liver toxicities that could affect your general health. It is important to monitor the albumin, alkaline phosphatase, and bilirubin to ensure a well functioning liver. Another important focus of this test is monitoring your lipid levels in the heart. This test helps monitor LDL cholesterol (the bad cholesterol), HDL cholesterol (the healthy cholesterol), and triglycerides. It is important to be aware of these lipids, to help monitor the potential for heart disease. With the Chem-Screen this test should be taken every three months and the results take 2-3 days to be completed by the laboratory.


 Laboratory Report 
Client Name: Smith, Bob
Date Drawn: 5/21/06
Date of Report: 5/29/06
ID Number: 692271440
 
Account Number: 12687
Test Name
Result
Reference Range
HIV 1 RNA PCR
265 (High)
<50 Copies/mL
Absolute CD4+ Cells
102 (Low)
490 - 1740 per CMM


Lab tests are an invaluable part of your comprehensive HIV health care to help with monitoring HIV progression. These tests can be a good indicator to detect a problem. However, when using your labs as a comparison tool to monitor your health, it is important to recognize that one unexpected test result may not necessarily signal a major problem with your health, and trends in your results over time are more important than relying on a single lab test. Also, there are many factors that can create variability in your tests results, and always remember if you are not comfortable with your first blood work tests, request that your doctor perform another test. It is important for everyone to have a general understanding on how to read a summary of lab results. However, it is even more important that you talk with your doctor about your lab results, ask him/her to help you with the interpretation of the results, and how it may affect your treatment plan.

Sarah Biel-Cunningham is the Director of Peer Services for AIDS Survival Project. sbiel@aidssurvivalproject.org.




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