The combined diagnostic and therapeutic value of ultrasound and X-ray bone age index in girls with idiopathic central precocious puberty.

Objectives: The objectives of this study are threefold: first, to evaluate the diagnostic utility of ultrasound in combination with radiographic bone age assessments for identifying idiopathic central precocious puberty (ICPP) in girls; second, to determine the efficacy of treatment; and third, to establish comprehensive models for both diagnosis and therapeutic evaluation. Methods: Female patients diagnosed with 96 cases of ICPP in our hospital from January 2022 to February 2024 were assigned to the research group, while 94 girls with premature thelarche from the same period were designated as the control group. Both groups underwent ultrasound examinations (of the uterus, ovaries, and breasts) and X-ray bone age evaluations, and their serum endocrine hormone levels (luteinizing hormone and follicle-stimulating hormone) were measured. Differences in ultrasound parameters, bone age indices, and hormone levels were analyzed between the research and control groups. Univariate and multivariate LASSO regression were employed to screen imaging parameters, and a LASSO-logistic regression model was established to create a combined predictive model. Receiver operating characteristic curves were plotted to investigate the diagnostic efficacy of the individual and combined models in ICPP. The general clinical data and imaging parameters of the ICPP group were compared before and after treatment, with ultrasound and bone age indices used in combination to assess therapeutic efficacy. Results: The LASSO regression screened important predictive indicators, including the bone age index (BAI), mean bilateral breast thickness, uterine longitudinal diameter, uterine anteroposterior diameter, uterine transverse diameter, endometrial thickness, mean bilateral ovarian length, and the mean number of ovarian follicles with a diameter >4 mm. These imaging parameters were incorporated into a logistic regression model, which demonstrated good discriminatory power with an AUC value of 0.895 (95% CI: 0.851, 0.938). The combined model outperformed the model using ultrasound alone (AUC: 0.869 (95% CI: 0.820, 0.918)) and the BAI model (AUC: 0.758 (95% CI: 0.690, 0.826)), showing superior discrimination and calibration. In the follow-up evaluation of the ICPP group post-treatment, ultrasound parameters such as uterine anteroposterior diameter, mean bilateral ovarian length, mean number of ovarian follicles with a diameter >4 mm, mean maximum follicular diameter, and mean bilateral ovarian volume showed good monitoring efficacy (AUC >0.7). In addition, the uterine longitudinal diameter and BAI exhibited high specificity. Together, these indicators achieved a combined diagnostic AUC value of 0.877 with 75% sensitivity and 87% specificity. Conclusions: To enhance diagnostic precision and overcome the constraints of single-metric evaluation approaches, a composite model was constructed by integrating ultrasound-based parameters with radiographic bone age measurements.