Understanding Your Lab Work (Blood Tests) (2023)

Viral Load Test

CD4 Cell Count

ChemScreen

Complete Blood Count (CBC)

VIRAL LOAD TEST

This test measures the number of copies of HIVgenetic material in a small amount of blood. Two types of HIVgeneticmaterial may be measured, RNAor DNA. RNAtests are usually used for routine blood monitoring, butDNAtests can sometimes detect hidden HIVeven if an RNAtest is undetectable.

There is no normal rangefor viral load—the point of HIV treatment is to keep itas low as possible for as long as possible. Standard HIVRNA viral loads testsusuallycan measure down to 50or sometimes 20 copies. If your result comes back “not detected” or “undetectable,” your viral load is very low, known as viral suppression. Some tests used for research are more sensitive and can measure down to a single copy.

Viral load tests are used tomonitor how well HIV treatment is working and whether it’stime to switch to a new regimen. When starting treatment, certain HIVmedications are not recommended for people with a high viral load above 100,000 copies. Some treatment combinations, known as maintenance therapy, are only recommended for people who are switching medicationsafter they already have an undetectable viral load.

Department of Health and Human Services (DHHS) guidelines recommend getting a viral load test when you first seek care for HIV, when antiretroviral treatment is started or modified and again at two to eight weeks after starting or switching therapy. If viral load is detectable at that point, testing should be repeated every four to eight weeks until it falls below 200. After that, viral load should be monitored every three to six months. Viral load should also be tested if treatment appears to be failing or if clinically indicated.

Once a person is on treatment and has achieved viral suppression, viral load can rise again for a few reasons.

Sometimes an occasional, temporary rise called a “blip” can occur. This could be due to a lab error orindicate that a person has another infection,but often there is no known reason.This is usually nothing to worry about.

However, a trend of increasing viral load over time is a bigger concern. This could mean a person is struggling with adherence or having trouble getting refills consistently. It could also mean that a drug interaction is preventing the HIV meds from fully controlling the virus. In any case, this should be discussed and resolved with your health care provider.<

Increasing viral load over time can also mean that HIVhas developed resistance to one or more drugs in the regimen. If this happens, it’s important to get a genotypic resistance test done; this test is best when viral load is at least 1,000 copies. If resistance is detected, the regimen should bechanged to include drugs that can fully suppress HIV.

Here’s what a viral load test report looks like:

HIV-1 RNA

The number of copies ofHIVRNA found by the test.HIV-1 is the most common type ofHIV seen in the U.S. (HIV-2 is usually found in West and Central Africa.)Three testing techniques may be used: RT-PCR(or simply PCR), branchedDNA(bDNA) orNASBA.

Log Copies/ML

A “log” is a term scientists use torefer to amounts; in this case, it is copies of HIVRNA. In the simplest terms, 1 log represents one “0”. Therefore, 2 logmeans 100 copies, 3 logmeans 1,000 copies (or more accurately 10 x 10 x 10), etc. Logs are also used to measure changes in viral load. For example, a viral load that goes from 100,000 down to 100 is a 3-log reduction.

CD4 CELL COUNT

A CD4 T cell is a type of immune system white blood cell.These cells coordinate the activities of other cells in the immune system that fight viruses, bacteria and cancers.

HIV prefers toenter CD4 cells in order to reproduce. This kills the cells, causing their number to decrease over time. Having too few CD4 cells means that the immune system will no longer function like it is supposed to.

There are several types of white blood cellscarry out immune responses. These include two types of lymphocytes: B cells and T cells. Both are made in your bone marrow, but B cells stay there to mature while T cells move the thymus to mature. B cells produce antibodies, which help your bodyfight harmfulinvaders such as bacteria, viruses and fungi.

T-cells are divided into three groups:

• Helper T cells (T4 or CD4 cells) coordinate the activity of other types of immune cells.
• Killer T cells (atype of CD8 cell) recognize and destroy abnormal cells, such as cancer cells and cells infected with viruses.
• Suppressor T cells (also a type of CD8 cell) limit the activity of otherimmune cells so they don’tharm normal tissue.

Getting regular CD4 counts will show how healthy your immune system is and whether your antiretroviral treatment is working. CD4 levels used to be used to figure out when to start treatment, but now antiretroviraltherapy is recommended for everyone diagnosed with HIV. People with very low CD4 counts may needadditional medications to prevent AIDS-related infections.

DHHSguidelines recommend getting a CD4 test every three to six months during the first two years on treatment, if your viral load rises while on treatment or if your CD4 count is below 300. After you’ve been on treatment with stable viral suppression for two years, CD4 tests can be done once a year if your count is between 300 and 500, or skipped entirely if it’s above 500.

The following is an example of a lab report for T cell measurements. The numbers represent the amounts found in a small drop of blood called a cubic millimeter. You will usually see a range of numbers listed for each test result, so you can compare your numbers to what is the normal range for most HIV-negative people.

CD3 Absolute Count

The number of all T cells, which includes CD4 and CD8 cells. This figure is rarely used for making treatment decisions.

CD3 Percentage

Theproportion of all immune cells that are T cells. This figure is also rarely used for making treatment decisions.

CD4 Cell Count

The absolute number of CD4 cells. The normal range for an HIV-negative person is 500 to 1,500. The goal of HIV treatment is to keep this number as high as possible for as long as possible. A CD4 count below 200 indicates an AIDS diagnosisand raises the risk for opportunistic infections.

CD4 Percentage

The CD4 percentage, or the proportion of all T cells that are CD4 cells. This may be more reliable because it tends to vary less than the CD4 count.The normal range for HIV-negative adultsis 30% to 60%; people with HIV often have a lower percentage. A percentage below 14% indicates an AIDS diagnosis. CD4 percentage, rather than CD4 count, is used to monitor disease progression in children.

CD8 Cell Count

The absolute number of all CD8 cells,which include both killer and suppressor T cells. The normal range for an HIV-negative person is 150 to 1,000. It is usually higher in a person with HIV. This figure is rarely used for making treatment decisions.

CD8 Percentage

The proportion of all T cells that are CD8 cells. The CD8 percentage is sometimes more reliable because it tends to vary less than the CD8 count.

CD4/CD8 Ratio (helper cell/suppressor cell ratio)

The CD4/CD8 ratio, or the CD4 count divided by the CD8 count, gives a fuller picture of immune system health. The normal range for HIV-negative people is around 1.0 to 4.0, or one to four CD4 cells for every CD8 cell. People with uncontrolled HIV may have fewer CD4 cells than CD8 cells, indicated by a ratio less than 1.0.

CHEMSCREEN

A chemistry screen reports the amounts of various chemicals in the blood. While itdoesn’t really tell you much about HIV or how your immune system is doing, it can reveal a lot about your overall health, including metabolicstatus and liver or kidney problems. Several of these measurements couldindicate drug side effects.

DHHS guidelines recommend getting a basic chem screen when you first seek HIV care, when you start or switch treatment and again at two to eight weeks after starting or switching therapy. After that, these tests can be done every six months and whenever clinically indicated. If your doctor does glucose and lipid testing separate from the chem screen, these can be done every year.

Here’s what a chemscreen report looks like:

/p>

Glucose

The food you eat is processed into glucose (blood sugar), fats (lipids) and proteins in the body. Glucose levels in the blood are most reliably measured after fasting, for example in the morning before eating.

Cholesterol and Triglycerides

Lipids include triglyceridesandcholesterol, which in turn is broken down into low-density lipoprotein (LDL), known as “bad” cholesterol, and high-density lipoproteins (HDL), or “good” cholesterol. Having elevated triglycerides and LDL is a risk factor for cardiovascular disease, while a high HDL level is protective. Having a higher proportion of HDL relative to total cholesterol, known as thetotal cholesterol/HDLratio, is better. Some HIV meds can alter triglyceride and cholesterol levels.

Electrolytes

Sodium,potassium,chloride,bicarbonate,phosphate,calciumandmagnesiumare all electrolytes—the charged particles that make up a salt. Electrolytes play a crucial role in maintaining the body’s pH (acidity level), and they affect various cell functions and the electrical activity of the heart. Abnormal electrolyte levels may result from persistent diarrhea or vomiting or chronic conditions such as kidney dysfunction.

Iron

Iron is an important mineral that is a component of hemoglobin, the protein in red blood cells that transports oxygen to all cells and tissues in the body. A low level can be a sign of anemia or internal bleeding and should be followed up by a health care provider.

Blood Proteins

Albuminandglobulinare the two types of protein included in the total protein measurement. Albumin is a blood protein that helps maintain the fluid balance in the bloodstream. Globulins play a role in liver function, blood clotting and immune function. One type, immunoglobulins—better known as antibodies—fight infections. Thealbumin/globulin, or A/G ratio,reflects the amount of albumin relative to the amount of globulin in the blood. Some people withHIVhave below-normal A/G ratios, though this usually isn’t anything to worry about, as long as albumin levels are normal.

Kidney Biomarkers

BUN (Blood Urea Nitrogen),creatinineanduric acidare waste products in your blood and urine. Because your kidneys excrete these wastes into your urine,levels in the blood are used to monitor kidney function. Many drugs, including some HIV meds, can affect BUN and creatinine levels and theBUN/creatinineratio.

Liver Biomarkers

Bilirubin(total and direct),alkalinephosphatase,gamma-glutamyl transferase (GGT), alanine transaminase (ALT) and aspartate transaminase AST) are enzymes produced by the liver. Elevated levels can indicate liver problems, which may be due to medication side effects, viral hepatitis, fatty liver disease or other causes. Elevated bilirubin can cause the skin and eyes to look yellowish.

Other Biomarkers

Amylaseis a digestive enzyme produced by the salivary glands and pancreas. An elevated level can indicate swelling or inflammation of the pancreas (pancreatitis), is side effect of some olderHIVmeds.LD orLDHstands for lactatedehydrogenase, an enzyme involved in energy production. An elevated level can indicate acute or chronic tissue damage and, along with other lab tests, it may help diagnose liver disease,pancreatitis, certain cancers or other problems.

COMPLETE BLOOD COUNT (CBC)

One of the most important blood tests that your doctor will orderisa complete blood count (CBC), which is an inventory of the different types of blood cells. These can be grouped into three categories: red blood cells, white blood cells and platelets.Knowing how many of these cells are in a blood sample provides a lot of valuable information.

DHHS guidelines recommend a CBCwhen you first seek HIV care, when you start or switch treatment and then every three to six months along with a CD4 count. If you are on stable treatment and your CD4s are no longer being monitored regularly, get a CBC every year or if clinically indicated.

Here’s what aCBC report looks like. The reference ranges shown below are for adult males. Some may vary for women, children and adolescents. Check your lab report for specific reference ranges.

White Blood Cells (WBC)

White blood cells, or leukocytes are immune system cells that defend the body against invaders and cancers. They are formed in bone marrow and either enter the blood or migrate to key organs such as the spleen, lymph nodes or gut. White blood cells include lymphocytes, neutrophils and monocytes. Some CBC reports include a differential section that breaks out their numbers and percentages. B cells and T cells (CD4 and CD8 cells) are types of lymphocytes, but they are not typically broken out in a standard CBC report (see CD4 Cell Count, above). A highWBCcount may indicate that an infection is present, while a low number might indicate that an infection ordisease—suchasHIVorcancer—hasreduced the bone marrow’s ability to produce newcells; some drugs also cause bone marrow damage.

Red Blood Cells (RBC)

Red blood cells, or erythrocytes, are responsible for delivering oxygen throughout the body. There are between 3.6 to 6.1 million of these cells in a single milliliter of blood. A low RBC count can indicate anemia, which can lead to fatigue. Some olderHIVmedscan cause anemia, as can some AIDS-related infections and cancers. A high count can occur in people with low oxygen levels, for example due to heart disease or chronic lung disease.

Hemoglobin (HGB) andHematocrit(HCT)

Hemoglobin andhematocritprovide more information about red blood cells. Hemoglobin is the protein in red blood cells that transports oxygen.Hematocritrefers to the proportion of blood that is made up of red blood cells. For men, thehematocritshould be between 40% and 52%; for women, it should be between 35% and 46%. A low hemoglobin level orhematocritpercentage may indicate anemia.

Mean Corpuscular Volume (MCV)

This test measures the size of red blood cells. Larger red blood cells may indicate anemia due to vitamin B6 orfolicacid deficiency while smaller red blood cells may indicate anemia due to iron deficiency. Some olderHIVmeds can causechanges in MCV.

Mean Corpuscular Hemoglobin (MCH) and Mean Corpuscular Hemoglobin Concentration (MCHC)

These tests measure the amount of hemoglobin in red blood cells. Low levels indicate anemia.

Red Cell Distribution Width (RDW)

Since red blood cells can come in different sizes,RDWlooks at the range of these sizes in a blood sample. If anemia is suspected,RDWtest results are often used together withMCVto figure out what the cause might be.

Platelets

Platelets are tiny cell fragments that enable the blood to clot in case of injury, but excessive clotting can lead to blockage of arteries or veins. A high platelet count might be seen in people with certain types of cancer, rheumatoid arthritis or inflammatory conditions. A low platelet count, calledthrombocytopenia, is often seen in people with HIV, liver disease and certain types of cancer, and it can occur as a side effect of drugs that damage the bone marrow. Thrombocytopenia can lead to bleeding and bruising. It’s important

Last Reviewed: March 30, 2021

Read More About:

• #CD4
• #lab test
• #viral load test