Figure 1.

Median factor I levels in patients with AMD and controls. A sandwich ELISA was used to measure the FI level (µg/mL) in the plasma of patients in the Southampton AMD cohort. These levels were measured in triplicate and calculated as an interpolation of OD values on a computer-generated standard curve resulting from 1:2 dilutions of purified FI starting from 1 µg/mL and ending at 0.004 µg/mL. The median level was significantly lower in cases compared to controls (P = 0.0034, interquartile range shown, for 276 cases and 205 controls). A low fifth percentile of 23.69 µg/mL was calculated from the healthy control cohort only and is indicated by the dotted line. **P < 0.01.