CHEMISTRY (CHEM) SCREEN

A large part of your laboratory report is results of the chemistry screen. These tests measure various chemicals in your blood to see whether your body is working correctly.

Laboratories have different "reference ranges" or normal values for the results of each test. Most lab reports show the normal range and highlight any test results outside the normal range.

The mineral calcium is a major component of bones and teeth. Calcium is also needed for nerves and muscles to work properly, and in chemical reactions in the cells. The body controls the amount of calcium in the blood. However, the amount of protein in the blood can affect calcium test results (see albumin). The most common cause of low calcium test results for people with HIV is low protein levels due to malnutrition or wasting. Abnormal calcium levels can indicate digestive problems.

Phosphorus, like calcium, is a major component of bones. Low levels of phosphorus for a long period of time can cause damage to bones, nerves and muscles. High phosphate levels are most often due to kidney failure.

Glucose is sugar, which is broken down in the cells to provide energy.

THE ELECTROLYTES
The electrolytes are related to fluid balance in your cells. They are especially important if you become dehydrated or have kidney problems.

• Sodium levels indicate your balance of salt and water. They also are a sign of the functioning of your kidneys and adrenal glands. Abnormal blood sodium levels often indicate that blood volume is too low (due to dehydration) or too high. They can also occur when the heart is not pumping blood normally, or when the kidneys are not working properly.
• Potassium affects several major organs including the heart. Potassium levels rise in kidney failure, and may be abnormal due to vomiting or diarrhea.
• Chloride levels often go up and down along with sodium levels. This is because sodium chloride, or common salt, is a major component of blood.
• Bicarbonate or CO2 measures a buffer system in the blood. A normal CO2 level keeps the blood acidity at the correct level. A high level might be caused by high levels of lactic acid in the blood.

• ALT (alanine aminotransferase), formerly called serum glutamate pyruvate transaminase or SGPT)
• AST (aspartate aminotransferase), formerly called serum glutamic-oxaloacetic transaminase or SGOT)
• Bilirubin (a yellow fluid produced when red blood cells break down). Note: The antiviral drugs indinavir (Crixivan®) and atazanavir (Reyataz®) can increase bilirubin.
• Alkaline Phosphatase
• GGT (gamma glutamyl transpeptidase)
• LDH (lactic dehydrogenase, not the same as lactic acid)