Understanding Your Laboratory Test: What It Is, How It Is Done, and What Your Results Mean

This test is a laboratory analysis performed on a small sample of your blood, urine, or other body material to help your doctor evaluate how well your body is working and to look for signs of illness or disease. It may be ordered during a routine health checkup, to investigate specific symptoms you are experiencing, or to monitor a condition you already have.

This test, also called cephalometric analysis, measures a specific angle (ANB angle) on a special X-ray of your head called a cephalogram. The measurement shows the relationship between your upper jaw, lower jaw, and the base of your skull. It helps doctors understand how your jawbones are positioned relative to each other and plan appropriate treatment.

The test is usually performed by a trained health care professional who collects a sample from you, most often by drawing blood from a vein in your arm with a sterile needle. The collection typically takes only a few minutes, and you may feel a brief pinch or sting. The sample is then sent to a laboratory where specialized equipment and trained staff analyze it.

You will sit or stand in a special X-ray machine with your head positioned precisely against a support. The machine takes a side-view X-ray of your entire skull and jaw area. The dentist or orthodontist then traces specific points on the X-ray (nasion, A point, and B point) and calculates the angle between them. The procedure is quick, painless, and takes only a few minutes.

Your results are compared with reference ranges that show the values considered typical for healthy people. Values within these ranges generally suggest normal function, while values that are higher or lower may point to an infection, a deficiency, or another condition that needs closer attention. Your doctor will review the report with you, explain what each finding means, and discuss any follow-up steps.

The ANB angle typically ranges from 1 to 4 degrees in a normal bite. An angle less than 1 degree may suggest a skeletal Class III bite (lower jaw protrudes). An angle greater than 4 degrees may indicate a skeletal Class II bite (upper jaw protrudes). Your doctor will compare this with other measurements to create a complete picture of your jaw and facial structure.