Labs and diagnostics

Letting x-rays pass through, so the material looks dark on an x-ray image and does not hide what lies behind it.

Blocking x-rays, so the material shows up white on an x-ray image.

A blood test used to screen for syphilis by looking for antibodies the body makes during the infection.

A blood cell that carries oxygen from the lungs to the body's tissues; also called an erythrocyte.

A blood test that counts the red blood cells in a set amount of blood.

The range of results for a lab test that is expected in healthy people, also called the normal range.

The bending of light as it passes from one clear material into another, as it does through the cornea and lens; also the eye test that measures it.

The air left in the lungs after breathing out as hard as possible.

A state in which the blood becomes too acidic because the lungs do not remove enough carbon dioxide.

An acid-base imbalance in which breathing out too much carbon dioxide makes the blood too alkaline.

A blood test that measures reticulocytes, young red blood cells newly released from the bone marrow.

A protein that may be present on the surface of red blood cells; people who have it are Rh-positive and those without it are Rh-negative.

Reverse transcription polymerase chain reaction: a lab test that finds the genetic material of a virus or other germ in a sample.