How often should a Dual-Energy X-ray Absorptiometry (DEXA) scan be repeated?

DEXA Scan Repeat Frequency

For most patients with normal bone density or mild osteopenia, repeat DEXA scanning every 2 years is appropriate, while high-risk patients requiring glucocorticoids, cancer treatments affecting bone, or those with significant osteopenia plus risk factors should undergo annual scanning. 1

Standard Repeat Intervals by Clinical Scenario

Normal Bone Density (Low-Risk Patients)

• Repeat DEXA every 2-3 years for patients with normal BMD and no additional risk factors 1
• For childhood, adolescent, and young adult cancer survivors with normal BMD at entry into long-term follow-up, repeat at age 25 years when peak bone mass is achieved, rather than at fixed intervals 2, 1
• Extended intervals beyond 3 years may be considered for truly low-risk patients based on individual assessment 1

Osteopenia (T-score between -1.0 and -2.5)

• Repeat every 2 years for patients with mild to moderate osteopenia without additional risk factors 1, 3
• Repeat annually if significant risk factors for accelerated bone loss are present 3
• Between baseline and age 25 surveillance, perform BMD testing as clinically indicated based on ongoing risk assessment 2

High-Risk Populations Requiring Annual Monitoring

• Glucocorticoid therapy >3 months: repeat annually (every 1-2 years) 1, 3
• Cancer treatments affecting bone (aromatase inhibitors, androgen deprivation therapy, chemotherapy-induced ovarian failure): repeat annually 1, 3
• Chronic conditions accelerating bone loss (chronic renal failure, rheumatoid arthritis, inflammatory bowel disease, eating disorders, malabsorption): repeat annually 3
• Female athletes with Female Athlete Triad risk factors (eating disorders, amenorrhea, prior stress fractures): repeat every 1-2 years 1
• Advanced cirrhosis or awaiting transplantation: repeat annually 1

Critical Technical Principles

Timing Constraints

• BMD measurements should NEVER be performed more frequently than once per year 1, 3
• Intervals less than 1 year rarely provide clinically meaningful information due to slow bone density changes and measurement variability 1, 3
• The least significant change (LSC) is calculated as 2.77 × precision error, requiring adequate time intervals to detect meaningful changes 2

Ensuring Accurate Comparisons

• Always use the same DXA machine for follow-up scans to enable precise comparisons 2, 1, 3
• Maintain same software, scan mode, patient positioning, and anatomical side (hip/forearm) 2
• Compare absolute BMD values (g/cm²), NOT T-scores or Z-scores, between serial measurements 2, 1, 3
• Each center should calculate its own precision error using 30 duplicate or 15 triplicate scans 2
• Maximum acceptable LSC for technologists is 5.0% for total hip and 5.3% for lumbar spine 2

Common Pitfalls to Avoid

Measurement Errors

• Do not use manufacturer's LSC without local confirmation due to considerable variation between machines and centers 2
• Recognize that degenerative changes can falsely elevate BMD values, particularly in the spine 1
• Long-term precision (typical clinical practice) is approximately twice the short-term precision, with CVs of 2.3-2.7% versus 1.2-1.4% 4

Interpretation Errors

• Only changes meeting or exceeding the LSC should be considered significant 2
• Absolute change in BMD (g/cm²) is preferred over percentage change for LSC calculations in clinical practice 2
• Be aware that BMD measurements may underestimate changes by approximately 25% due to correlations between bone area and bone mineral content 4

Special Monitoring Situations

After Treatment Initiation

• Once osteoporosis treatment is started, repeat DEXA every 2 years or as clinically indicated 3
• There is good evidence that BMD reduction with treatment is proportional to fracture risk reduction 5
• Measuring BMD is useful following discontinuation of osteoporosis treatment 5

Abnormal Results Requiring Action

• Z-score <-2: refer to bone health specialist for further endocrine evaluation, interpretation, treatment, and follow-up 2
• Z-score between -1 and -2: evaluate for endocrine defects (hypogonadism, growth hormone deficiency) and consult specialist as clinically indicated 2
• If BMD decline exceeds the machine's least significant change, repeat after 2 years and thereafter as clinically indicated 2