Joris van Dongen

210 Chapter 9 Regressionanalysis of pre-operativeR7parameteras a functionof age showedanegative correlation in both groups, comparable to Enzure et al. 21 . However, after intervention, the correlation reverses (Fig. 6), which could be a sign of facial rejuvenation. Changes were most noticeable in the PRP+ group: the high prediction value of the regression line (R=0.542, p=0.055) could suggest that sample size in this study was not adequate. Interestingly this reversal was only notable on Location 1 R7, not on location 2 nor with the R5-R6 parameters. A B Figure 6. Regression analysis of true skin elasticity as a function of age, before and 12 months after intervention. All measurements and the calculated regression curve with 95% C.I. are presented A: PRP-. Pre-operatively age correlates negatively with true elasticity (y= -0.003293*x+0.4343 R=0.402 p=0.195), but this correlation reverses 12 months post-operatively (y= 0.002005*x+0.1507” R=0.326 p=0.299). B : PRP +. Again, a negative correlation before operation (y= -0.002444*x+0.3471” R=0.392 p=0.184), with a stronger reversal after intervention (y= 0.005078*x+0.01921” R=0.542 p=0.055) compared to PRP -. Volumetric changes of the nasolabial fold Summarized data from both groups, at every follow-up moment are presented in Figure 7, lower scores represent a less prominent nasolabial fold. Grading scores showed a high level of agreement between each expert (all Spearman ICC r >0.576, p<0.001). Pre-operative scores were comparable in both groups (PRP-: μ:2.359 ±0.1531, PRP+: μ:2.622 ±0.2388, p>0.05). Data after 3 months and 1 year also showed comparable