By Dr. Chao Yuan-ping, Department of Family and Community Medicine

In 1994, the World Health Organization (WHO) provided a conceptual definition of osteoporosis as a "progressive systemic skeletal disease characterized by reduced bone mass and microarchitectural deterioration of bone tissue, leading to increased bone fragility and fracture risk." The Taiwanese Osteoporosis Association (TOA) has been releasing clinical guidelines since 2002, with updates every two years. These guidelines cover prevention and treatment of osteoporosis, aiming to provide optimal clinical guidance.

Osteoporosis typically doesn't manifest significant symptoms, earning it the moniker of a "silent disease." For many older adults, the only noticeable signs may be a reduction in height or changes in posture, such as kyphosis. These patients often remain unaware and may not feel the need to address it. However, even minor falls or exertion, such as bending over to lift objects, can lead to fractures. Once a fracture occurs, patients may face severe pain, limited mobility, impacting their quality of life, and even posing life-threatening risks. Potential risk factors for osteoporosis include age, female gender, low body mass index, history of fractures, family history of hip fractures, smoking, excessive alcohol consumption, certain diseases that promote bone loss, use of medications that promote bone loss, and prolonged bed rest/weakness/lack of activity. Statistics suggest that approximately one-third of Taiwanese women and one-fifth of Taiwanese men will experience at least one fracture event in their lifetime, with higher risks for those with chronic diseases.

The diagnosis of osteoporosis can be confirmed through clinical history to identify low-trauma fractures or by calculating the T-score after bone density testing. The gold standard for measuring bone density is through central dual-energy X-ray absorptiometry (DXA). DXA measurements should include at least two sites, typically the lumbar spine and hip. If these sites cannot be measured due to fractures, measurement at the non-dominant forearm's one-third distal radius can be considered. Quantitative ultrasound (QUS) is currently suitable only as a preliminary screening tool, and if abnormalities are detected, confirmation with DXA should follow.

Since the fracture rates among Taiwanese people are similar to those of Caucasians, the reference values for T-score calculation for both men and women are compared to the average values of young Caucasian women (aged 20-29). T-score interpretation is applicable to menopausal women, postmenopausal women, and men over 50 years old. According to WHO definitions, a T-score of ≥-1.0 is considered normal; between -1.0 and -2.5 indicates osteopenia or low bone mass; and a T-score of ≤-2.5 indicates osteoporosis. For other patients, the International Society for Clinical Densitometry (ISCD) recommends using Z-scores, which are adjusted for race, age, and gender, to diagnose osteoporosis.

Once the diagnosis of osteoporosis is established, it's crucial to identify any potential secondary causes. Clinically, this involves obtaining a detailed medical history, conducting a physical examination, and reviewing medication history. Subsequently, appropriate blood tests and examinations are conducted based on the potential differential diagnoses. As per expert recommendations, basic tests include complete blood count, liver and kidney function tests, blood calcium, phosphate, vitamin D, and parathyroid hormone levels, thyroid function, and sex hormone levels to rule out common causes of secondary osteoporosis. If these tests fail to identify the cause or if newly diagnosed patients have multiple fractures or a T-score less than -3.0, specialized tests may be considered to determine other underlying causes.

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2. Tai, T.W., et al., Clinical practice guidelines for the prevention and treatment of osteoporosis in Taiwan: 2022 update. J Formos Med Assoc, 2023. 122 Suppl 1: p. S4-s13.

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