A Risk Score to Identify Low Bone Mineral Density for Age in Young Patients with Anorexia Nervosa.

OBJECTIVE

Developing a scoring assessment tools for the determination of low bone mass for age at lumbar spine and hip in patients with anorexia nervosa (AN).

METHODS

The areal bone mineral density (aBMD) was determined with dual-energy X-ray absorptiometry (DXA). In 331 women with AN and 121 controls, aged from 14.5 to 34.9 years, univariate and multivariate logistic regression analyses were performed to address the association of Z-score aBMD evaluated at lumbar spine and hip with several parameters.

RESULTS

For the lumbar spine and hip, the three risk factors significantly and independently associated with Z-score aBMD were age of patients (variable in class ≥20 year vs. <20 year), minimal disease-related BMI (continuous variable), and duration of amenorrhea without contraceptive use (variable in class ≥18 months vs. <18 months), with close values for the odds ratio for the two bone sites. A simple risk score equation was developed and tested combining only these three parameters. The AUC's measuring the score's performance were, respectively, 0.85 [95% CI: 0.79-0.90] with a sensitivity of 83% and specificity of 71%, and 0.82 [95% CI: 0.76-0.86] with a sensitivity of 92% and specificity of 55% to detect low aBMD in lumbar spine and hip. The cut-off values for low bone mass for age were 0.9 and 1.33 for the two bone sites. The prediction model revealed that a minimum of 83% of the patients presenting low bone mass for age were correctly identified.

CONCLUSIONS

the study presents for the first time a risk score for diagnosing low bone mass for age in young patients with AN. Considering its excellent sensitivity, and its ease of use, requiring only three parameters that are well identified in this disease, this new score may be useful in clinical settings when DXA scans are not feasible.