Table 6. Multiple regression analyses of 5HT-induced aggregation parameters.

	Regression coefficient	95% confidence intervals	P value
A) (Ln) total aggregation
5HT (µmol/L)	0.000036	6.8×10−6, 0.000065	0.018
Ferritin (µg/L)	−0.027	−0.043, −0.011	0.002
Serum iron (µmol/L)	−0.082	−0.14, −0.028	0.005
Iron*ferritin (µg*µmol/L2):	0.0012	8.7×10−6, 0.0024	0.052
B) (Ln) rate of aggregation
Ferritin (µg/L)	−0.0062	−0.010, −0.0022	0.004
Serum iron (µmol/L)	−0.040	−0.061, −0.019	0.001

A) The distribution for aggregation achieved was skewed and normalised by log transformation (Figure S2A). (Ln)aggregation was therefore used as the dependent variable for regression. A model restricted to first order variables was not as strong as the final model including the iron-ferritin interaction term (iron*ferritin (µg*µmol/L²)). This model of 24 assays explained 72% of the variance of (ln)aggregation (p = 0.0001). B) The distribution for rate of aggregation was skewed and normalised by log transformation (Figure S2B). (Ln)rate of aggregation was therefore used as the dependent variable for regression. Final model for (ln)rate of aggregation in all 22 available assays, in a model that explained 77.4% of the variance (p<0.0001).The crude coefficient with iron was similar at −0.036 [95% CI −0.053, −0.0187], p<0.0001. There was no relationship with 5HT concentration in univariate or iron/ferritin- adjusted regression (data not shown).