Percentage of Participants With a Mean RGI-C Global Score ≥ +2.0 (Responders) at Week 40
RGI-C responders are defined as participants with a mean RGI-C global score >= +2.0. The RGI-C is a 7-point ordinal scale with possible values: +3 = very much better (complete or near complete healing of rickets), +2 = much better (substantial healing of rickets), +1 = minimally better (i.e., minimal healing of rickets), 0 = unchanged, -1 = minimally worse (minimal worsening of rickets), -2 = much worse (moderate worsening of rickets), -3 = very much worse (severe worsening of rickets).
Percentage of Participants With a Mean RGI-C Global Score ≥ +2.0 (Responders) at Week 64
RGI-C responders are defined as participants with a mean RGI-C global score >= +2.0. The RGI-C is a 7-point ordinal scale with possible values: +3 = very much better (complete or near complete healing of rickets), +2 = much better (substantial healing of rickets), +1 = minimally better (i.e., minimal healing of rickets), 0 = unchanged, -1 = minimally worse (minimal worsening of rickets), -2 = much worse (moderate worsening of rickets), -3 = very much worse (severe worsening of rickets).
RGI-C Global Score at Week 64
Changes in the severity of rickets and bowing were assessed using a disease specific qualitative RGI-C scoring system. The RGI-C is a 7-point ordinal scale with possible values: +3 = very much better (complete or near complete healing of rickets), +2 = much better (substantial healing of rickets), +1 = minimally better (i.e., minimal healing of rickets), 0 = unchanged, -1 = minimally worse (minimal worsening of rickets), -2 = much worse (moderate worsening of rickets), -3 = very much worse (severe worsening of rickets).
Change From Baseline in RSS Total Score at Week 40
The RSS system is a 10-point radiographic scoring method that was developed to assess the severity of nutritional rickets in the wrists and knees based on the degree of metaphyseal fraying, cupping, lucency, separation, and the proportion of the growth plate affected. Scores are assigned for the unilateral wrist and knee X-rays deemed by the rater to be the more severe of the bilateral images. The maximum total score on the RSS is 10 points and the minimum score is 0, with a total possible score of 4 points for the wrists and 6 points for the knees (the total score is the sum of the wrist and knee score). Higher scores indicate greater rickets severity.
Change From Baseline in RSS Total Score at Week 64
The RSS system is a 10-point radiographic scoring method that was developed to assess the severity of nutritional rickets in the wrists and knees based on the degree of metaphyseal fraying, cupping, and the proportion of the growth plate affected. Scores are assigned for the unilateral wrist and knee X-rays deemed by the rater to be the more severe of the bilateral images. The maximum total score on the RSS is 10 points and the minimum score is 0, with a total possible score of 4 points for the wrists and 6 points for the knees. Higher scores indicate greater rickets severity.
RGI-C Long Leg Score at Week 40
Changes in the severity of lower extremity skeletal abnormalities, including genu varum and genu valgus, were assessed using a disease specific qualitative RGI-C scoring system. The RGI-C is a 7-point ordinal scale with possible values: +3 = very much better (complete or near complete healing), +2 = much better (substantial healing), +1 = minimally better (i.e., minimal healing), 0 = unchanged, -1 = minimally worse (minimal worsening), -2 = much worse (moderate worsening), -3 = very much worse (severe worsening).
RGI-C Long Leg Score at Week 64
Changes in the severity of lower extremity skeletal abnormalities, including genu varum and genu valgus, were assessed using a disease specific qualitative RGI-C scoring system. The RGI-C is a 7-point ordinal scale with possible values: +3 = very much better (complete or near complete healing), +2 = much better (substantial healing), +1 = minimally better (i.e., minimal healing), 0 = unchanged, -1 = minimally worse (minimal worsening), -2 = much worse (moderate worsening), -3 = very much worse (severe worsening).
Change From Baseline in Height-For-Age Z-Scores to Week 40
Recumbent length/Standing height z scores are measures of height adjusted for a child's age and sex. The Z-score indicates the number of standard deviations away from a reference population (from the Centers for Disease Control [CDC] growth charts) in the same age range and with the same sex. A Z-score of 0 is equal to the mean with negative numbers indicating values lower than the mean and positive values higher. Higher Z-scores indicate a better outcome.
Change From Baseline in Height-For-Age Z-Scores to Week 64
Recumbent length/Standing height z scores are measures of height adjusted for a child's age and sex. The Z-score indicates the number of standard deviations away from a reference population (from the CDC growth charts) in the same age range and with the same sex. A Z-score of 0 is equal to the mean with negative numbers indicating values lower than the mean and positive values higher. Higher Z-scores indicate a better outcome.
Change in Growth Velocity Z Score From Baseline to Week 40
A growth velocity Z score was calculated based on Tanner's standard. The Z score indicates the number of standard deviations away from a reference population (from Tanner's standard) in the same age range and with the same sex. The baseline growth velocity was calculated for participants who had data available from within 1.5 years prior to baseline. The Week 64 growth velocity was calculated using data between baseline and Week 64. The mid-point of the age interval was used to locate the closest reference age provided by Tanner's Standard. Children with a mid-point age under 2.25 years were excluded, because younger ages are not available in Tanner's standard. To smoothly transition from recumbent length to standing height, 0·8 cm was subtracted from recumbent length before pooling with standing height. A Z score of 0 is equal to the mean with negative numbers indicating values lower than the mean and positive values higher. Higher Z scores indicate a better outcome.
Change in Growth Velocity Z Score From Baseline to Week 64
A growth velocity Z score was calculated based on Tanner's standard. The Z score indicates the number of standard deviations away from a reference population (from Tanner's standard) in the same age range and with the same sex. The baseline growth velocity was calculated for participants who had data available from within 1.5 years prior to baseline. The Week 64 growth velocity was calculated using data between baseline and Week 64. The mid-point of the age interval was used to locate the closest reference age provided by Tanner's Standard. Children with a mid-point age under 2.25 years were excluded, because younger ages are not available in Tanner's standard. To smoothly transition from recumbent length to standing height, 0·8 cm was subtracted from recumbent length before pooling with standing height. A Z score of 0 is equal to the mean with negative numbers indicating values lower than the mean and positive values higher. Higher Z scores indicate a better outcome.
Change From Baseline Over Time in Serum Phosphorus Concentration, up to Week 64
The GEE model includes change from baseline for serum phosphorous measurement as the dependent variable, treatment group, visit, interaction between treatment group by visit, baseline age and baseline RSS stratification as factors, baseline phosphorous measure as a covariate, with exchangeable covariance structure. The GEE model included data up to Week 64.
Change From Baseline Over Time in Serum Phosphorus Concentration, Weeks 66-112
Change From Baseline in Mean Post-Baseline Serum Phosphorus Level to Week 64
The ANCOVA model includes change in serum phosphorus from baseline to mean post-baseline as the dependent variable, treatment group, baseline age and baseline RSS stratification as factors, baseline phosphorous measure as a covariate.
Change From Baseline in Mean Post-Baseline Serum Phosphorus Level to Week 140 (During Treatment With Burosumab)
Percentage of Participants Reaching the Normal Range of Serum Phosphorus Concentration (3.2 - 6.1 mg/dL)
Change From Baseline Over Time in 1,25-Dihydroxyvitamin D, up to Week 64
The GEE model includes change from baseline for 1, 25-Dihydroxyvitamin D measurement as the dependent variable, treatment group, visit, interaction between treatment group by visit, baseline age and baseline RSS stratification as factors, baseline 1, 25-Dihydroxyvitamin D measure as a covariate, with exchangeable covariance structure. The GEE model included data up to Week 64.
Change From Baseline Over Time in 1,25-Dihydroxyvitamin D, Weeks 68 to 112
Change From Baseline Over Time in TmP/GFR, up to Week 64
Serum phosphorus and TRP measurements were used in the calculation of TmP/GFR.
The GEE model includes change from baseline for TmP/GFR measurement as the dependent variable, treatment group, visit, interaction between treatment group by visit, baseline age and baseline RSS stratification as factors, baseline TmP/GFR measure as a covariate, with exchangeable covariance structure. The GEE model included data up to Week 64.
Change From Baseline Over Time in TmP/GFR, Week 68 to 112
Serum phosphorus and TRP measurements were used in the calculation of TmP/GFR.
Change From Baseline Over Time in Serum ALP, up to Week 64
The GEE model includes change from baseline for ALP measurement as the dependent variable, treatment group, visit, interaction between treatment group by visit, baseline age and baseline RSS stratification as factors, baseline ALP measure as a covariate, with exchangeable covariance structure. The GEE model included data up to Week 64.
Change From Baseline Over Time in Serum ALP, Week 68 to 112
Percent Change From Baseline Over Time in Serum ALP, up to Week 112
Decreases indicate improvement.
Change From Baseline in the PROMIS Pediatric Pain Interference, Physical Function Mobility and Fatigue Domain Scores (For Participants ≥ 5 Years of Age at the Screening Visit) at Week 40
The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013), (NIH 2015). It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Pain Interference Domain, decreases indicate less pain, for the Physical Function Mobility Domain, increases indicate greater mobility and for the Fatigue Domain, decreases indicate less fatigue.
Change From Baseline in the PROMIS Pediatric Pain Interference, Physical Function Mobility and Fatigue Domain Scores (For Participants ≥ 5 Years of Age at the Screening Visit) at Week 64
The PROMIS was developed by the National Institutes of Health and uses domain-specific measures to assess patient well-being (Broderick et al. 2013), (NIH 2015). It uses a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. For the Pain Interference Domain, decreases indicate less pain, for the Physical Function Mobility Domain, increases indicate greater mobility and for the Fatigue Domain, decreases indicate less fatigue.
Change From Baseline in the FPS-R (For Participants ≥ 5 Years of Age at the Screening Visit) at Week 40
The FPS-R is a dimensionless 10 point Likert scale used to assess self-reported pain intensity on a scale from 0 (no pain) to 10 (most pain you can imagine). Greater pain scores are indicative of more severe pain.
Change From Baseline in the FPS-R (For Participants ≥ 5 Years of Age at the Screening Visit) at Week 64
The FPS-R is a dimensionless 10 point Likert scale used to assess self-reported pain intensity on a scale from 0 (no pain) to 10 (most pain you can imagine). Greater pain scores are indicative of more severe pain.
Change From Baseline in the 6MWT Total Distance at Week 40
The total distance walked (meters) in a 6-minute period was measured in participants ≥ 5 years of age at the Screening Visit who were able to complete the test.
Change From Baseline in the 6MWT Total Distance at Week 64
The total distance walked (meters) in a 6-minute period was measured in participants ≥ 5 years of age at the Screening Visit who were able to complete the test.
Percent of Predicted Normal in the 6MWT Total Distance at Week 40
The total distance walked (meters) in a 6-minute period was measured in participants ≥ 5 years of age at the Screening Visit who were able to complete the test, and the percent predicted distance based on normative data for age and gender was estimated.
Percent of Predicted Normal in the 6MWT Total Distance at Week 64
The total distance walked (meters) in a 6-minute period was measured in participants ≥ 5 years of age at the Screening Visit who were able to complete the test, and the percent predicted distance based on normative data for age and gender was estimated.