Table 1 Comparison of mean total peak area from the complete (0–78 min) and truncated spectra (40–78 min) between the control and autistic groups, using uncorrected and creatinine corrected data
Total peak areaMean values (SE)567
Control(n = 158)Total cases(n = 65)Autism(n = 58)Asperger syndrome (n = 7)p Value,control/casesp Value,all groupsSize of difference detectable
A. Complete spectrum*1209 (18)1229 (28)1219 (30)1311 (86)0.550.51±7.9%
B. Truncated spectrum*506.8 (8.0)518.1 (12.4)516.9 (13.2)528.6 (37.9)0.440.71±8.2%
C. Creatinine adjusted complete spectrum†2.685 (0.003)2.690 (0.005)2.691 (0.005)2.683 (0.014)0.340.56±0.6%
D. Creatinine adjusted truncated spectrum†2.558 (0.003)2.567 (0.005)2.569 (0.006)2.545 (0.016)0.180.16±0.7%
E. Creatinine content*28.58 (0.62)27.7 (0.96)27.09 (1.02)32.55 (2.93)0.440.16±11.3%
  • *Using square root transformed data; †using repeated log transformed data.

  • A comparison of the creatinine concentration in the urine is also shown. The final column presents the minimum difference between the control and autistic spectrum disorder groups detectable at 8% statistical power given the observed variability, as a percentage of the observed mean of the control group. SE, standard error.