Color analytical reader for procalcitonin colloidal gold test strips

The semi-quantitative method of Colloidal gold strip detection by colorimetric principle is widely used in biomedical diagnosis. To achieve quantitative measurement of calcitonin concentration, a CMOS color analytical reader based on raspberry Pi was designed for the acquisition of color characteristics of chromogenic reaction by taking a picture of colloidal gold strip. According to the color characteristics of procalcitonin colloidal gold test strips, the CMOS sensor was corrected by proper white balance parameter adjustment, which enabled the CMOS image sensor has a better color restoration property. In order to eliminate the difference of color management between different devices, the mathematical model of the sensor from RGB space to XYZ space was established via polynomial regression by taking pictures of NCS standard color cards. Thus the instrument was adjusted in color characteristics. Then, the mathematical model of XYZ values and concentration values of the samples was derived from the representative gray value pixel areas of the processed images, thereby the color uniformity problem was solved and the concentration was accurately measured. The experiment results show that the measuring precision can be as high as 93.8%, the repeated measurement error is less than 1.5% and the effective measurement range is from 0.1 ng/mL to 35 ng/mL. With the virtues of cost effective and high measurement speed, the analyzer has a promising application prospect.