IS GROWTH TRAJECTORY AS ASSESSED BY THE MULTIPLIER METHOD AFFECTED BY PHYSIOLOGICAL AGE

Introduction: Paley et al has developed a multiplier method for calculating both leg length and total height. In the development of this algorithm, they evaluated the effect of factors including bone age and sex. They established that sex had a significant impact, but adjusting for bone age did not improve accuracy. Bone age and menarche have been shown to improve other height prediction models. Purpose: We used a large prospective cohort to evaluate if the multiplier is independent of physiological age using menarche as a proxy. Methods: Using the ALSPAC dataset we determined the accuracy of the Paley multiplier for predicting total height and leg length, and assed weather if the date of first menses increased the accuracy of the multiplier. Female patients over the age of 8, with documented final height and final sub-ishial leg length over the age of 15 and a date of first menses were evaluated. Predicted final height was compared with actual final height at all data points. Results: There were 28332 data points in 3062 girls prior to skeletal maturity in the total height cohort and 8395 data points in 2300 girls in the leg length cohort. When age was corrected using the difference in age at onset of menarche from average, the accuracy of multiplier decreased for both measurements. When a correction of 50% was used, there was an improvement in the accuracy of multiplier predictions, reducing the average error by up to 24%. Conclusions: Previous studies have failed to demonstrate that the accuracy of the multiplier is improved when adjusted for bone age. We have used the date of first menses as a proxy for bone age and established that making a 50% correction for physiological age improves the accuracy of this method. Significance: This will potentially allow more accurate prediction of leg length discrepancy, and total height in girls with early menarche.