Who is at risk of fracture? Avoid 6 pitfalls of osteoporosis screening

In general, the relationship between bone mineral density (BMD) and fracture risk is continuous, graded, and inverse.¹

Diagnosis of osteoporosis should be based on the lowest BMD measurement (hip or spine). For example, if the spinal BMD is a T score of –2.7 and the hip is –1.9, the patient would have a diagnosis of osteoporosis because of the low spinal score.

Laboratory studies. Once osteoporosis is diagnosed, secondary causes of the disease should be ruled out. Laboratory evaluation is helpful, especially if the Z score is at or below –2. Routine tests should include:

• Complete blood count and erythrocyte sedimentation rate, to rule out multiple myeloma, a more common malignancy in the elderly
  
• Serum calcium, which is elevated in hyperparathyroidism but low in malabsorption syndrome and vitamin D deficiency
  
• Albumin
  
• Urinary calcium, which is low in vitamin D deficiency and malabsorption syndrome, but elevated in hyperthyroidism, hyperparathyroidism, multiple myeloma, and renal disease
  
• Free thyroxine, which is high in hyperthyroidism
  
• Thyroid-stimulating hormone, which is low in hyperthyroidism but high in hypothyroidism⁸
  

TABLE 1

Defining osteoporosis: World Health Organization thresholds

PITFALL #1An inadequate history

Peak bone mass. By the time a woman reaches her postmenopausal years, bone density has been influenced by specific factors. One is the peak bone mass she achieved as a young adult. Skeletal growth is nearly complete by age 18, and different skeletal sites reach their peak density at different times.

For example, the spine reaches maturity at 21 to 27 years, and the hip at 19 to 24 years.⁶ If skeletal growth and nutrition are adequate in the formative years, optimal peak bone mass in adulthood is likely; if not, it is unlikely. These patients have lost more bone by menopause than their healthy counterparts.⁹

Peak bone mass status is not readily apparent. The clinician needs to specifically ask about the woman’s adolescence and early adulthood, as well as lifestyle, past and current nutrition, and genetic factors, to determine her risk for osteoporosis (TABLE 2). For example, a family history of osteoporosis, particularly in the patient’s mother or another first-degree relative, is a good predictor of osteoporosis.

Other predisposing genetic factors include Caucasian and Asian race and a slender frame (body mass index below 20). African-American women have been shown to have higher BMD than white women.^2,3

Lifestyle factors contributing to osteoporosis include tobacco use, high alcohol intake, and a diet deficient in calcium and vitamin D.

TABLE 2

Risk factors for osteoporosis

PITFALL #2Overlooking symptoms

If a woman complains of acute or chronic back pain, the clinician should consider the possibility of osteoporotic vertebral fractures. With these fractures, pain generally originates in the middle back and is characterized by acute onset.¹⁰

Excessive exercise that leads to amenorrhea can cause bone loss that is not fully recoverable.

Vertebrae T12 and L1 are the most common fracture sites, with T6 through T9 following closely.¹⁰ Multiple compression fractures may cause kyphosis–one of the obvious signs of osteoporosis.

But the disease is not always so blatant. Wrist fracture and/or tooth loss are other, earlier signs.

Who is at risk of fracture?

Even when a 50-year-old woman and a 75-year-old woman have the same bone mineral density, the older woman is far more likely to experience a fracture.

Another clue to the presence of osteoporosis is loss of height, which is also caused by vertebral fractures. For this reason, the patient’s height should be measured at each visit, and she should be asked about her maximum remembered height. A loss of 1.5 inches or more is cause for screening.

PITFALL #3Skipping the topic of exercise

Weight-bearing and high-impact exercises such as jumping and running appear to benefit the skeleton, especially the peripheral skeleton. The lumbar spine is less responsive. Muscle-strengthening also can lead to beneficial bone building.