WHO Guidelines for Osteoporosis Diagnosis: A Comprehensive Guide

Oct 25, 2025 4 min read •

Health bone health Medical Guidelines

According to the World Health Organization (WHO), osteoporosis is defined by a bone mineral density (BMD) value 2.5 standard deviations or more below the mean peak bone mass of young healthy women. These WHO guidelines for osteoporosis diagnosis provide the foundation for identifying individuals at high risk for fractures, allowing for timely intervention and treatment.

Quick Summary

This guide details the diagnostic criteria established by the World Health Organization for identifying osteoporosis. It explains the significance of T-scores derived from DXA scans, outlines the classification thresholds, and explores how the FRAX assessment tool can be used to predict fracture risk in conjunction with BMD measurements.

Key Points

T-Score as Standard: The WHO defines osteoporosis based on a T-score of -2.5 or lower, as measured by a DXA scan, primarily at the femoral neck.
Low Bone Mass (Osteopenia): A T-score between -1.0 and -2.5 indicates low bone mass, which is a risk factor for osteoporosis.
Role of FRAX: The WHO's FRAX tool assesses the 10-year probability of fracture, combining BMD with clinical risk factors like age, sex, BMI, and previous fracture history.
Diagnosis by Fracture History: A history of a fragility fracture, particularly of the hip or vertebra, can be diagnostic of osteoporosis, even without a T-score of -2.5 or lower.
Comprehensive Assessment: A complete diagnosis considers T-scores, clinical risk factors, and fragility fractures to determine overall fracture risk, not just low BMD.
Context for Use: The WHO criteria apply to postmenopausal women and men aged 50 or older; for younger individuals, different Z-score criteria and clinical assessment are used.

Understanding the WHO Diagnostic Criteria

The World Health Organization's diagnostic criteria for osteoporosis are based on bone mineral density (BMD) measurements from a Dual-Energy X-ray Absorptiometry (DXA) scan. This is the gold standard for diagnosis in postmenopausal women and men aged 50 and over. The results are reported as a T-score, which compares a person's BMD to the peak bone mass of a healthy young adult reference population.

The Role of the T-Score

The T-score is the cornerstone of the WHO's classification system. It quantifies the difference between an individual's BMD and the mean BMD of a healthy young adult in units of standard deviation (SD). A positive T-score means bone density is above the young adult mean, while a negative T-score indicates lower bone density. The lower the T-score, the weaker the bones and the higher the risk of fracture.

Here is how the WHO categorizes bone density based on T-scores:

Normal: T-score is at -1.0 and above.
Low Bone Mass (Osteopenia): T-score is between -1.0 and -2.5.
Osteoporosis: T-score is at -2.5 or below.
Severe Osteoporosis: T-score is at -2.5 or below and the person has experienced one or more fragility fractures.

Expanding the Diagnosis Beyond BMD

While the T-score is critical, the WHO and related guidelines have evolved to recognize that a patient's overall fracture risk involves more than just BMD. Most fractures occur in individuals with low bone mass (osteopenia), not just osteoporosis, because this group is much larger. As a result, other factors are now integral to a complete diagnosis.

In addition to a T-score of -2.5 or lower, osteoporosis can be diagnosed in postmenopausal women and men over 50 based on the following:

A history of low-trauma or fragility fracture, particularly of the hip or vertebrae.
A T-score between -1.0 and -2.5 (osteopenia) combined with an elevated fracture risk as determined by the FRAX assessment tool.

The Fracture Risk Assessment Tool (FRAX)

The Fracture Risk Assessment Tool (FRAX) is an algorithm developed by the World Health Organization to evaluate a person's 10-year probability of experiencing a major osteoporotic fracture. It is especially useful for individuals with osteopenia, as it can help identify those who are still at high risk despite not meeting the full T-score criteria for osteoporosis. FRAX incorporates several clinical risk factors for fracture, which are largely independent of BMD.

Clinical Risk Factors in FRAX

For a comprehensive assessment, FRAX considers a range of factors that influence fracture probability:

Age: Fracture risk increases with age.
Sex and BMI: Gender and Body Mass Index are significant risk factors.
Prior Fracture: A history of a previous fragility fracture indicates increased risk.
Parental History of Hip Fracture: A family history of hip fractures is a strong predictor.
Medication Use: Long-term oral glucocorticoid use raises fracture risk.
Secondary Osteoporosis: Conditions like rheumatoid arthritis or type 1 diabetes contribute to risk.
Lifestyle Factors: Current smoking and excessive alcohol intake are also included.

Comparing Diagnostic Methods: BMD vs. FRAX


Feature	DXA T-Score (BMD)	FRAX Assessment Tool
Primary Purpose	Defines bone mineral density and categorizes bone health (Normal, Osteopenia, Osteoporosis).	Predicts 10-year absolute fracture probability for both hip and major osteoporotic fractures.
Patient Focus	All postmenopausal women and men aged 50+.	Especially useful for patients with osteopenia, to further assess fracture risk.
Data Inputs	Bone mineral density measurement from a central DXA scan, typically at the hip and spine.	Clinical risk factors (age, sex, BMI, fracture history, parental hip fracture) and optionally, femoral neck BMD.
Key Outcome	T-score value, indicating how far above or below peak bone mass the individual is.	10-year probability of fracture, expressed as a percentage.
Limitations	Diagnosis based on T-score alone can miss many individuals who will suffer a fracture.	Can underestimate fracture risk in individuals with high risk for falling, recent fractures, or multiple fractures.

The Final Diagnosis and Action

A final diagnosis of osteoporosis is based on a holistic assessment that combines BMD results, risk factors, and potentially FRAX scores. A low-trauma fracture at the hip is diagnostic of osteoporosis, regardless of the BMD T-score. For patients with osteopenia (T-score between -1.0 and -2.5), the FRAX tool becomes crucial. In many countries, treatment is recommended if the 10-year probability of hip fracture is $\ge$ 3% or major osteoporotic fracture is $\ge$ 20%.

Monitoring and Treatment

Once a diagnosis is made, treatment focuses on reducing fracture risk. This includes pharmacological options, lifestyle modifications, and fall prevention strategies. DXA scans are also used to monitor the effectiveness of treatment over time. The decision to treat is a clinical judgment, weighing the patient's individual circumstances, risk factors, and the potential benefits and risks of therapy. The WHO's frameworks, including BMD criteria and the FRAX tool, provide essential, evidence-based guidance for clinicians globally.

Conclusion

The WHO guidelines for osteoporosis diagnosis emphasize a multifaceted approach that extends beyond simple bone mineral density measurements. By incorporating T-scores from DXA scans, the presence of fragility fractures, and the robust risk assessment provided by the FRAX tool, clinicians can more accurately identify individuals at high risk for future fractures. This comprehensive methodology ensures that interventions can be targeted to those who will benefit most, improving patient outcomes and addressing the significant public health burden of osteoporosis.

External Resource: For a deeper dive into the FRAX tool and guidelines, you can visit the International Osteoporosis Foundation website.

Frequently Asked Questions

The primary WHO criteria for diagnosing osteoporosis is a bone mineral density (BMD) T-score of -2.5 or lower, measured by a DXA scan at the hip, spine, or femoral neck.

According to WHO guidelines, osteoporosis is defined by a T-score of -2.5 or lower, while osteopenia (or low bone mass) is defined by a T-score between -1.0 and -2.5.

The FRAX tool, developed with support from the WHO, is used to estimate a person's 10-year fracture risk. It is particularly helpful for patients with osteopenia, as a high FRAX score can lead to an osteoporosis diagnosis and recommended treatment.

Yes. A diagnosis of osteoporosis can also be made if you have a fragility fracture (a fracture from minor trauma), especially at the hip or spine, regardless of your T-score.

A fragility fracture is a bone fracture that occurs from a degree of trauma that would not normally cause a fracture, such as a fall from standing height or less.

The core T-score criteria were initially for postmenopausal women and men aged 50+. For premenopausal women, men under 50, and children, the diagnosis is more complex and typically requires a Z-score of -2.0 or lower, combined with a history of fragility fractures, as recommended by the International Society for Clinical Densitometry (ISCD).

DXA scans for osteoporosis diagnosis typically measure bone density at the lumbar spine, total hip, and femoral neck. The one-third (33%) radius can also be used if the hip or spine cannot be measured.

References

Medical Disclaimer

This content is for informational purposes only and should not replace professional medical advice. Always consult a qualified healthcare provider regarding personal health decisions.