Making the Diagnosis of Osteoporosis
Bone Mineral Density and T-scores
Osteoporosis is a condition of decreased bone mass. This leads to fragile bones which are at an increased risk for fractures. In fact, it will take much less stress on an osteoporotic bone to cause it to fracture than it would on a healthy bone.
The term "porosis" means porous, which describes the appearance of osteoporosis bones were they to be broken in half and the inside examined. Normal bone marrow has small holes within it, but a bone with osteoporosis will have much larger holes. .
There is no method of determining the actual structure of bones without removing a piece during a biopsy (which is not practical or necessary). Instead, the diagnosis of osteoporosis is based on special x-ray methods called densitometry. Densitometry will give accurate and precise measurements of the amount of bone (not their actual quality) in different parts of the body. This measurement is called bone mineral density or BMD.
The World Health Organization (WHO) has established criteria for making the diagnosis of osteoporosis, as well as determining levels that predict higher chances of fractures. These criteria are based on comparing the BMD of the patient with that of a typical healthy, young female's.
BMD values that fall well below the average for the healthy, young female's (stated statistically as 2.5 standard deviations below the average) are diagnosed as osteoporotic. If a patient has a BMD value less than the healthy, young female, but not 2.5 standard deviations below the average, the bone is osteopenic. Osteopenic means decreased bone mineral density, but it's not as severe as osteoporosis.
Although these criteria are widely used, they were based on a Caucasian female, so there will be some differences when these levels are applied to non-Caucasian females or to males in general. Despite this flaw, BMD measurement is a common method that's helpful in all groups.
The Importance of Testing in Osteoporosis Diagnosis
Osteoporosis is different from most other diseases or common illnesses in that there is not a single cause.
The overall health of a person's bones is determined by many things, ranging from how well the bones were formed as a youth to the person's physical activity level over the years.
During the first 20 years of life, the formation of bone is the most important factor. After that point, it is the prevention of bone loss that becomes most important. Anything that causes decreased bone formation early in life, or loss of bone structure later in life, may lead to the disease.
Testing will help determine if you are at risk for osteoporosis. From there, you can determine whether you need to make certain lifestyle changes to prevent osteoporosis and fragile bones that are subject to fracture.