Objective To analyze the diagnostic value of ultrasound combined with Z-score in various types of precocious puberty of girls.

Methods Ultrasound was used to measure the uterus and ovary of normal girls aged between 3 and 21, and Z-score model was established. Ultrasound was used to measure the uterus and ovary of girls with central precocious puberty (CPP), peripheral precocious puberty (PPP), premature pubarche (PP), and premature thelarche (PT). The highest age-related variable was selected to calculate the Z value of the above measurements. The best diagnostic cut-off point was obtained by ROC curve.

Results Ovarian volume and uterine body length had the best correlation with age. The ovarian volume and uterine body length of the girls with CPP were longer and larger than those in normal girls. The area under curve (AUC) of ovarian volume was 0.94 and the best diagnostic cut-off value was Z=2.16 (sensitivity 100%, specificity 81.1%). The AUC of uterine body length was 0.845 and the best diagnostic cut-off value was Z=1.14 (sensitivity 91.6%, specificity 84.9%). In the girls with PPP, only the length of uterine body was longer than that of normal girls. The AUC was 0.910 and the best diagnostic cut-off value was Z=1.06 (sensitivity 98.0%, specificity 82.0%). There was no significant difference between the girls with PP, PT and normal girls.

Conclusion Ultrasound combined with Z value has certain significance in differentiating CPP from PPP. It is speculated that this method can be used in the treatment and monitoring of precocious puberty.