Comparison of Quantile Regression and Gaussian (Z-scores) Percentiles to BSA in Growth Charts With a Pakistani Population.

Introduction: In the current study, we construct growth charts of body surface area (BSA) for adults using the quantile regression (QR) approach and growth charts of different Gaussian Percentiles (Z-scores) against age. Methods: A cross-sectional data consisting of 3,473 individuals aged 5 or more, both males and females were taken from Multan city. Quantile regression (QR) was used to construct BSA growth charts. Growth charts for different Z-scores were also constructed. Results: For our data set, the mean BSA is 0.48750. The BSA percentiles show a trending higher after the age of 5 until the age of 22, then decrease between age 22 and 35, and then finally increase after age 35. The Z-score curve increases slightly after age 5 and then proceeds higher until age 22. After age 22 and before 35 it plateaus and then increases slightly after age 35. Conclusion: Since the use of empirical BSA percentiles and Z-scores with grouped age provides a discrete approximation for the population percentiles and Z-scores, it is more accurate to use continuous BSA percentile and Z-score, curves against given ages while using quantile regression and Z-score approach. Furthermore, this approach can also be adopted to construct many other growth charts for physiological and medical sciences.