Osteoporosis: Risk factors and diagnosis
Osteoporosis, the thinning out and weakening of bones, is a progressive disease. It is generally an asymptomatic (silent) disease.
In Asia, it is mostly under-diagnosed and undertreated, but it is projected that by the year 2050, more than half of fractures due to osteoporosis will happen in Asia.
How is osteoporosis diagnosed and treated?
Medications, lifestyle modifications, and follow-up will be based on a person’s diagnosis.
Diagnosis starts with the identification of factors that put a person at risk for osteoporosis and fractures:
Medical history/interview and physical examination to answer these questions: Is there an underlying disease that causes osteoporosis? Is the person at risk for fracture? What are the simplest initial laboratory tests to support the diagnosis? Does the person need further laboratory studies and does he/she need to undergo tests to measure bone mineral density (BMD)?
BMD measurements confirm the diagnosis of osteoporosis and excellently predict future fracture risk. And if BMD measurement is necessary, the dual-energy X-ray absorptiometry or (DXA) of the hip and spine is the gold standard. The World Health Organization Fracture Risk Assessment Model or FRAX is also used clinically by doctors. This was developed to calculate the 10-year risk of osteoporosis fracture.
When is BMD measurement needed? The following are the indications:
Women 65 years or older or women less than 65 years old with one or more risk factor for fracture or osteoporosis;
All men more than 70 years of age, men 51 to 69 years old with risk factors, men more than 50 years old with history of fracture during adulthood;
Steroid therapy equivalent to 5mg/day or more, Prednisolone for three or more months or other medications associated with bone loss like anticonvulsants;
Low BMI: less than 20 kg/m2, body weight less than 127 pounds, loss of height, thoracic kyphosis;
Estrogen deficiency, hypogonadism, premature natural or surgical menopause (less than 45 years old), early menopause (less than 40 years old);
Hyperparathyroidism, hyperthyroidism, anorexia nervosa, malabsorption, Cushing’s Syndrome, prolonged immobilization (eg. bedridden), rheumatoid arthritis;
Evidence of low bone mass or vertebral deformity on radiologic studies; and
Postmenopausal women who had any type of fracture after the age of 50.
BMDs help identify patients for possible drug therapy and can also help in assessing response to treatment. The DXA scan is a rapid and painless imaging test that measures the amount of calcium and other minerals in the bone. It requires no preparation or injection. It involves lying on an X-ray table and not through a tube or tunnel.
The procedure takes 10 to 20 minutes, and only low-dose radiation is used. Images of the bone or skeleton are generated. The bone density is compared with the density expected for a young healthy adult of the person’s age, gender, and race/ethnicity. The difference is then calculated as a standard deviation or SD score. The difference between the person’s measurements and that of a young healthy adult is reported as the T-score.
The WHO classifies T-scores as normal, low bone mass (osteoponia), osteoporosis, or severe/established osteoporosis.
Other methods of BMD measurement are quantitative CT scan, which is used as an alternative procedure for DXA but it uses higher radiation dose. Trabecular Bone Score or TBScan also evaluate bone texture and predict fracture risk.
When a person more than 65 years old has several risk factors or has prevalent osteoporotic fracture, it is recommended by some medical authorities that treatment for osteoporosis be started even without BMD measurement.
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