Testing for Osteoporosis
Edition: September 2013 - Vol 21 Number 09
Patients sometimes do not know they have osteoporosis – a disease of the bones that results in extreme bone loss – until they are at the doctor’s office with a broken bone. Indeed, osteoporosis is responsible for about 2 million broken bones and $19 billion in related costs each year, according to the National Osteoporosis Foundation (NOF). And, the situation isn’t expected to improve any time soon. Experts estimate that by 2025, nearly 3 million fractures will occur each year, with related costs approaching $25.3 billion annually.
Referred to as the “silent disease,” osteoporosis often takes people by surprise, as there generally are no symptoms associated with it. People can’t feel their bones weakening, and often a broken bone is the first sign of the disease. Height loss and a curving spine also are signs of osteoporosis. In fact, in spite of the availability of bone density testing, which can help detect osteopenia (low bone density) or osteoporosis, about 48 million Americans have low bone density, and 9 million have osteoporosis, according to NOF. That means nearly 50 percent of all adults 50 years and older are at risk of breaking a bone.
Prior to testing for osteoporosis, physicians typically perform a physical and take a medical history to determine what, if any, factors place their patients at risk for the disease. For instance, the following may be of interest to physicians:
• Patient’s age and gender.
• Whether a female patient has reached menopause.
• History of broken bones as an adult.
• Family history of broken bones or osteoporosis.
• Smoking and drinking habits.
• Diet, including how much vitamin D or calcium the patient gets.
• Exercise and physical activity.
• History of an eating disorder.
• Regularity of periods in premenopausal women and testosterone levels in men.
In addition, some physicians may run a screening or peripheral test in the lower arm, wrist, finger or heel to help identify patients who are most likely to benefit from further bone density testing. These include:
• pDXA (peripheral dual energy X-ray absorptiometry).
• QUS (quantitative ultrasound).
• pQCT (peripheral quantitative computed tomography.)
A bone density test is the only test designed to diagnose osteoporosis before a broken bone occurs, according to NOF. The Foundation recommends a bone density test of the hip and spine by a central dual energy X-ray absorptiometry (DXA) machine, every one to two years. Exposure to radiation is minimal (between 10 and 15 times less than when flying roundtrip between New York City and San Francisco) and testing is non-invasive and painless and can be done safely in a hospital or office setting. The result is a set of diagnostic tools to detect and monitor the disease, including whether the patient:
• Has weak bones or bones with low density.
• Is at risk of breaking a bone in the future.
• Is on the right medication for osteoporosis.
• Has recently broken a bone due to osteoporosis.
The NOF recommends a bone densitometry test for the following patients:
• Women age 65 or older.
• Men age 70 or older.
• Patients who have broken a bone after age 50.
• Menopausal women with risk factors.
• Post-menopausal women under age 65 with risk factors.
• Men between 50 and 69 years with risk factors.
In addition, physicians should offer testing to patients who have experienced height loss or who have had an X-ray of their spine showing a break or bone loss in that area; patients who use medications known to cause bone loss, including corticosteroids, various anti-seizure medications and thyroid replacement drugs; patients with type 1 diabetes, kidney disease or liver disease; and patients with a thyroid or parathyroid condition, according to the Radiological Society of North America (RSNA).
NOF recommends that physicians use dual energy X-ray absorptiometry to test bones for density, although the type of equipment used may vary from one community to the next. Ideally, testing is done on the patient’s hip and spine. If necessary, however, NOF recommends a central DXA test of the radius bone in the forearm.
Generally, the patient remains fully dressed for a bone density test, which takes about 15 minutes. Some of the newer DXA systems are capable of measuring larger patients who weigh 400 pounds or more, but these machines are not always available, reports NOF.
Central DXA systems have large, flat tables and an arm suspended overhead. The DXA machine sends a thin, invisible beam of low-dose X-rays with two distinct energy peaks through the bones being examined. One peak is absorbed mainly by soft tissue, while the other is absorbed by bone. By subtracting the soft tissue amount from the total, the physician or radiologist can determine the patient’s bone mineral density, according to RSNA.
Reporting the results
Bone density tests are reported using T-scores, which show how much higher or lower the patient’s bone density is than that of a healthy 30-year-old adult. The World Health Organization interprets T-scores as follows:
• A score of -1.0 or above is normal bone density.
• A score between -1.0 and -2.5 signifies osteopenia, or low bone density.
• A score of -2.5 or below is a diagnosis of osteoporosis.
The bone density test also includes a Z score, which compares the patient’s bone density to that of an adult of similar size and age, with normal bone density. Many experts recommend using Z-scores for children, teens, pre-menopausal women and younger men, according to NOF. (NOF does not recommend routine testing for people in these categories.). The Society for Clinical Densitometry considers a Z-score above -2.0 normal.
While having osteopenia places one at higher risk for developing osteoporosis if he or she loses bone density in the future, it does not mean the patient definitely will progress to that point. Standard treatment guidelines for postmenopausal women and men age 50 or older are as follows:
• Most people with T-scores of -1.0 and above do not require osteoporosis medication, which help reduce the risk of broken bones.
• Some people with T-scores between -1.0 and -2.5 (osteopenia) should consider taking medication, depending on what other risk factors they have.
• All people with T-scores of -2.5 and below (osteoporosis) should consider taking medication.
When done correctly, using the right equipment, bone densitometry provides a valuable diagnostic tool for assisting with detection and treatment of osteopenia or osteoporosis. Sales reps can provide their physician customers with a service by educating them on their options.