This test screens for osteoporosis, degeneration of bone over time. The exam is usually done on the hip and spine. The main two exams used are DEXA or QCT, both forms of X-ray. The QCT, however, is a type of CT scan which gathers cross-sectional information and may be more precise.

Osteoporosis is generally an undiagnosed disease that is found only after an osteoporotic fracture has occurred. At this point, treatment is very difficult. Detection of osteoporosis allows for early treatment of the disease which can help reverse some of its effects and slow the development of painful symptoms. Both men and women can be affected. There is some controversy about the benefits of screening men, but the National Osteoporosis Foundation supports screening both men and women. In addition, screening may need to start at an earlier age for both men and women depending upon risk factors (see below). One way to evaluate risk is using an online tool called the FRAX calculator. This tool allows you to calculate the chance of having an osteoporotic fracture in the next 10 years.(The FRAX tool can take into account prior bone density test, but you do not need to enter this is you have not had it done.) A 65 year old female with no other risk factors is felt to have a 9.3% chance of fracture in her next 10 years of life, and this is a reasonable threshold to use for screening. A 55 year old female smoker whose mother had a hip fracture has about a 12% chance of fracture in the next 10 years (using the FRAX tool) and so she should undergo screening. Men are also at risk for osteoporosis and this is an underdiagnosed problem. There is some controversy about the benefits of screening men and the optimal intervals for repeat screening of men and women. Check with your doctor.

Generally you will lie on a table as the X-ray machine passes over and beside you. Usually a technologist performs the test and a radiologist interprets the results.

Jewelry and other metal can disturb the X-ray image so you will likely be instructed to refrain from wearing jewelry, metal belts, and zippers. Your will also probably be asked not to take calcium supplements during the 24 hours prior to the exam.

• advancing age
• female (men are also at risk)
• Family history
• Personal history
• Race: Caucasian, Asian
• Smoking
• Eating disorders
• Low body-weight
• Small frame
• Alcoholism
• Early menopause
• Inadequate weight-bearing exercise
• Low calcium intake
• Steroid use
• Tall height
• Diabetes
• Liver disease
• Kidney disease
• Thyroid conditions
• Immunodeficiency
• HIV
• Chronic obstructive pulmonary disease
• Inflammatory bowel disease
• Rheumatoid arthritis
• Low testosterone in men
• Medications including: steroids, cyclosporine A, methotrexate, heparin, cholestyramine, aluminum- containing antacids, anticonvulsants, excessive thyroid hormones
• Prolonged (>1 year) use of proton pump inhibitors or H2-blockers in patients over 50 years old