C H A N G E I N T O T A L B O D Y W A T E R A S A P R E D I C T I V E T O O L F O R G R O W T H H O R M O N E T R E A T M E N T R E S P O N S E composition was 0.68 (p = 0.001). This value is based on the mean difference of body composition before start of rhGH therapy (TBW / Height2) and after 6 weeks of rhGH therapy (TBW / Height2) within the GHD group and within the SGA group. Table 1: Baseline characteristics GHD n=88 SGA n=99 P-‐value Age (years) 8.30 (±3.6) 6.68 (±2.5) Height before therapy (SDS) -‐2.74 (±0.99) -‐3.27 (±0.69)* <0.001 Height after 1 year (SDS) -‐1.91 (±0.92) -‐2.40 (±0.73)* <0.001 Mean difference in height (SDS1year – SDSstart) 0.832 (±0.50) 0.874 (±0.33) 0.509 Body composition before therapy (TBW/height2) 9.60 (±1.31) 9.02 (±1.06)* <0.001 Body composition at 6 weeks (TBW/height2) 10.54 (±1.39) 9.70 (±1.10)* <0.001 Mean difference body comp (TBW/height2) 0.94 (±0.47) 0.68 (±0.47)* 0.001 Values are means ± standard deviation * significant difference compared to GHD Figure 1 shows the change in TBW divided by height2 over 6 weeks, plotted against the change in height during one year (SDS) for the GHD children. Two lines are shown. The reference line on the x-‐axis represents a change in height SDS of 0.7, which is the cut off value chosen between good (n=51) and poor (n=37) respond-‐ ers. The reference line on the y-‐axis represents the cut off value of the change in TBW/height2 of 0.7 l/m2. The four quadrants represent the true positive (B), false negative (C), true negative (D) and false positive (A) results. Based on the chosen cut off values, the sensitivity of TBW/height2 was 87% and the specificity 58%. The positive and negative predictive value is 73% and 75% respectively. The same is done in figure 2 for children born SGA, in which 25 had a poor growth response and 74 had a good growth response according to the cut off value of 0.7 SDS. This gives a sensitivity of 53% and a specificity of 83%, with a positive predictive value of 90% and a negative predictive value of 32% when using the cut off value of TBW/height2 of 0.7 l/m2. 49
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