Journal of Toxicology Severity of Autism Scale: 0: normal, 1: slight symptoms of autism, 2–4, mild symptoms of autism, 5–7, moderate symptoms of autism, 8–10, severe symptoms of autism. 63 participants were assessed with the ATEC, and 49 participants were assessed with the PDD-BI, SAS, and ADOS. Fewer participants were assessed for the latter three tests because some participants had low urinary excretion of toxic metals and were not eligible to continue, and some participants dropped out. Table 1 lists the characteristics of the participants. Table 2 lists their average urinary excretion of toxic metals before and after taking DMSA. 2.1. Regression Analysis. Regression analysis was employed to examine the relationship between the severity of autism (assessed by the ATEC, PDD-BI, SAS, and ADOS) and the urinary excretion of toxic metals, (both before and after taking DMSA), and further with the initial glutathione (in the red blood cells). For the selected dependent and independent variables, stepwise linear regression analyses were conducted: initially all independent variables were included in the regression; then at each step, the variable with the highest P-value was eliminated, and this process was continued until the adjusted R2 value began declining. Thus, the goal was to determine the best ﬁt to the sample data for the selected model, taking into account the correlation among the independent variables. Since the data had several missing values (due to missing lab or behavioural data), the regression analyses were conducted in two slightly diﬀerent ways which generally yielded very similar results: (1) eliminate all participants with missing data for any of the variables in the model at the beginning of the analysis, and (2) eliminate participants on an as-needed basis (i.e., only where there is missing data for any variable in the current step in the analysis). Since these two methods yielded very similar results, for brevity we only report the results for method 1. 3. Results 3.1. Correlations of Severity Scales. Table 3 shows the correla- tions among the assessment scales. There is a high correlation between the ATEC and the PDD-BI (r = 0.87), and a good correlation of the SAS with the ATEC (r = 0.70) and the PDD-BI (r = 0.72). The correlation of the ADOS with the other scales is somewhat lower (r = 0.60–0.67), probably since the ADOS evaluation was done by a professional evaluator, whereas the other assessments were done by the same parent. 3.2. Correlation Analysis. Table 4 shows the results of a simple correlation analysis of severity of autism versus toxic metal levels. Correlations with a P-value of less than .05 3 Total 63 57 6 5.6 ± 1.6 62 autism, 1 Asperger’s 62 ± 28 5.1 ± 2.2 15.8 ± 6.5 −54.3 ± 62 501 ± 246 micromolar After 9th dose versus baseline 638%∗∗∗∗ 314%∗∗ 128%∗∗ 111% 13% 42%∗∗∗ 42%∗ 18%∗∗ 21% 12% −14% −19%∗∗ −15%∗∗ Table 1: Characteristics of participants. The second number is the standard deviation. Total participants Male Female Age (years) Diagnosis ATEC (total) SAS ADOS (communication + social) PDD-BI (modiﬁed autism score) RBC glutathione (pre-DMSA) Creatinine ∗P < .1, ∗∗P < .05, ∗∗∗P < .01, ∗∗∗∗P < .001 Table 3: Correlation of autism severity scores. ATEC total SAS ADOS (social + communication) PDD-BI (modiﬁed autism score) ATEC SAS ADOS PDD-BI 1 0.70 0.60 0.87 1 0.60 0.72 1 0.67 1 are shown in bold. Baseline excretion of antimony (Sb) and excretion of lead (Pb) after the 9th dose of DMSA are the two most consistent factors, although other metals also have P < .05 for some of the severity scales. In all cases for P < .05, the correlations are positive, so that high levels of toxic metals Element Pb Sn Bi U Hg Tl Sb W Al Ni Cd As Baseline 1.3 ± 2.3 2.3 ± 3.4 0.18 ± 0.45 0.015 ± .04 0.86 ± .92 0.15 ± 0.12 0.10 ± 0.10 0.3 ± 0.29 16 ± 21 6.7 ± 5.1 0.38 ± 0.24 32 ± 20 94 ± 52 Table 2: Urinary excretion of toxic metals in Phase 1, at baseline and after 9th dose of DMSA, in mcg/g creatinine. Creatinine values have units of mg/dL. N = 63. The metals are listed in approximate order of eﬀect of DMSA on excretion. Signiﬁcant results are highlighted in bold font. After 9th dose 9.2 ± 7.8 9.7 ± 24 0.41 ± 1.0 0.031 ± .1 0.97 ± 0.88 0.21 ± 0.19 0.14 ± 0.20 0.46 ± 0.50 19 ± 33 7.6 ± 4.3 0.3 ± 0.23 25 ± 18 80 ± 43