Bone Mineral Density and Cystic Fibrosis

Over the last decade, CF researchers and physicians have observed that as patients with CF age, their metabolic rate (i.e. how much energy the body uses) changes are disease severity increases. Malabsorption issues are closely linked with poor performance on pulmonary function tests. It is of utmost importance that CF patients and their clinics work hard to maintain adequate nutritional status.

People with cystic fibrosis, especially those who are diagnosed as having pancreatic insufficiency, have great difficulty absorbing vital minerals and nutrients from food. Doctors regularly prescribe vitamin and mineral supplements for CF patients with the expectation and hope that semi-normal levels of these can be attained in the body.

Without sufficient concentrations of certain vitamins and minerals in the body, a patient with CF may develop bone density problems. As the number of patients exhibiting weak bones has increased, there is an added emphasis being placed on the necessity of what are called DEXA scans.

DEXA (dual energy x-ray absorptiometry) scans should be performed every three years to measure bone mineral density.

The procedure of a DEXA scan is painless and simple. The patient lies on his/her back on an examination table under a scanner arm. The scanner then uses x-ray beams from two different directions to the patient's body. The energy from the x-rays travels at a particular frequency, and is transmitted to a receiver that determines how quickly it moved through the bone. It does this by counting photons, which are energy particles. In places where the bone is denser, the x-ray beam slows down. By measuring these rates of transmission, overall bone density is calculated.

A computer takes the information about the number of photons and compares it to a normal, expected value. The result is called a "T" score. Different T scores can tell a doctor whether a patient is at risk for developing osteoporosis, or is perhaps exhibiting osteopenia.