We don't know whether to use a LDR or phototransistor to measure voltage on blood sample?

We are developing a tele-solution for offering gluco test for remote and rural population of India. We are working on developing a low cost gluco test kit comprising gluco meter and gluco strips. One of the functionalities we are looking is to measure the intensity of gluco strip colour after reaction. The other project we are working is on coming out with a automated gluco test on blood sample through the test-tube and re-agents.