Blood Chemistry Tests
As with the CBC, healthcare providers will often order blood chemistry tests on a regular basis to monitor your health. The blood chemistry test -- also known as the chem screen -- measures some of the most important chemicals produced and needed by your body to function properly. While abnormal chem screen test results don't usually mean that HIV disease is progressing, they can sometimes mean that another disease is present in the body or that a specific drug is causing side effects.
A chem screen can involve dozens of different tests, but usually measures between 6 to 24 chemicals. Some of the most important chemical levels in people living with HIV are discussed here:
Liver Enzyme Tests: ALT (SGPT) and AST (SGOT) are two important enzymes produced by the liver. The levels of these enzymes in the blood can vary considerably; the normal range of ALT is between 5 and 60 international units per liter (IU/L) and the normal range of AST is between 5 and 43 IU/L. Liver disease (such as viral hepatitis or liver tumors) and excessive alcohol consumption can cause these enzymes levels to increase.
Other liver tests to watch for include alkaline phosphatase, gamma GT (GGT or GGTP), LDH, albumin, and bilirubin. It is important that anyone taking antivirals and other medication -- especially those broken down by the liver (the protease inhibitors, for example) -- watch their liver function tests carefully. The protease inhibitors Crixivan (indinavir) and Reyataz (atazanavir) may cause elevations in bilirubin, which can result in jaundice (yellowing of the skin and whites of the eyes), but is usually harmless if levels don't become too high.
Kidney Tests: Blood urea nitrogen (BUN) and creatinine, both of which always appear on a chem screen report, are important blood values associated with kidney health. Normal BUN levels should be between 8 and 23 milligrams per deciliter of blood (mg/dL); normal creatinine levels should be between 0.7 and 1.3 mg/dL. These tests are very important to watch by people taking drugs that may affect the kidneys, such as Foscavir (foscarnet) and Vistide (cidofovir) for CMV and Viread (tenofovir) for HIV. Other important tests which can be affected by kidney function include phosphate and bicarbonate (carbon dioxide).
Pancreatic Tests: Amylase, an enzyme produced by the pancreas to aid in the digestion of carbohydrates is, when elevated, a strong indicator of pancreatic disease (pancreatitis). Pancreatitis, if not properly dealt with, can cause serious illness and even death. Drugs such as Videx/Videx EC (ddI) can cause pancreatitis, which is often reversible once the offending drug is stopped. Amylase is also found in saliva, and elevated blood levels of amylase are sometimes due to leakage from the salivary glands. Further tests can be done to distinguish between these two sources of amylase.
Electrolytes: Sodium, potassium, and chloride are electrolytes. Electrolytes play a crucial role in the operation of cells and the electrical activity of the heart. Sodium levels should be between 136 and 144 milliequivalents per liter of blood (mEq/L); potassium should be between 3.6 and 5.1 mEq/L; and chloride should be between 99 and 108 mEq/L. Very often, a person with HIV who is experiencing severe diarrhea or vomiting will have abnormal electrolyte levels. Medical care is often necessary for someone with electrolyte imbalances.
Nutritional Values: Food products, no matter what they are, take the form of glucose (sugars), proteins, or fats once inside the bloodstream. A balance of each is necessary to fulfill the body's energy needs and to keep all cells, tissues, and organs functioning properly.
Albumin is one of the major types of protein made by the liver and its level in the blood reflects both dietary intake of protein and the liver's ability to make proteins. Albumin levels, which are normally between 4 and 5 gm/dL, may be low in persons who are sick. Total protein levels, which are normally between 6.6 and 8.3 gm/dL, are often elevated in people with HIV because of abnormally increased production of antibodies.
Normal glucose levels should be between 65 and 125 milligrams per deciliter (mg/dL) of blood. For the most accurate results, it's best to check glucose levels before eating the first meal of the day (known as the fasting glucose level). Sometimes, a healthcare provider may order a post-prandial glucose test: the amount of glucose in the bloodstream two hours after eating a full meal containing sugar. Abnormally high glucose levels, especially fasting glucose levels, is usually a sign of diabetes. Medications like Glucophage (metformin), the "glitazones" Avandia (rosiglitazone) and Actos (pioglitazone), and insulin can be prescribed, along with dietary changes, to help control abnormally high glucose levels.
Normal triglycerides should be between 50 and 200 mg/dL. Like glucose levels, it's best to measure triglyceride levels first thing in the morning, before the first meal of the day. High triglyceride levels are associated with pancreatitis and, quite possibly, heart disease. Pancreatitis becomes a concern when the level of triglycerides is in the thousands. It's not clear if a moderately elevated triglyceride level -- triglycerides in the mid to high hundreds -- is associated with any immediate health risks. Fibric acid derivatives (fibrates), including TriCor (fenofibrate) and Lopid (gemfibrozil), can be prescribed for elevated triglyceride levels. TriCor is less likely to interact with anti-HIV medications than Lopid.
Cholesterol is another type of fat that is commonly measured in the blood. The three most important cholesterol tests to look for on a lab report are the amounts of total cholesterol, LDL cholesterol, and HDL cholesterol. Total cholesterol is the total amount of cholesterol in the bloodstream and includes both LDL and HDL cholesterol. The desirable total cholesterol level is anything below 200 milligrams per deciliter (mg/dL) of blood. The LDL cholesterol level is the amount of "bad" cholesterol in the bloodstream. The optimal LDL cholesterol level is below 100 mg/dL (the lower the better). LDL cholesterol levels above 160 mg/dL are considered high and increase the risk of cardiovascular disease. The HDL cholesterol level reflects the amount of "good" cholesterol in the bloodstream. A normal HDL cholesterol level is between 40 and 59 mg/dL. An HDL cholesterol level below 40 mg/dL can increase the risk of cardiovascular disease, as there isn't enough good cholesterol to help get rid of artery clogging caused by LDL cholesterol. Maintaining higher-than-normal HDL cholesterol levels -- meaning an HDL cholesterol level above 60 mg/dL -- may help reduce the risk of cardiovascular disease.