Home pregnancy kits typically provide a qualitative (yes/no) result based on the concentration of human chorionic gonadotropin (hCG) present in urine samples. We present an algorithm that converts this purely qualitative test into a semiquantitative one by processing digital images of the test kit's output. The algorithm identifies the test and control lines in the image and classifies an input into one of four different hCG concentration levels based on the color of the test line. The proposed algorithm provides significant improvement over a prior method and reduces the maximum false positive rate to less than 5%. This improvement is achieved by a careful choice of the color space so as to maximize the inter-concentration separability. Also, the proposed method increases the utility of the test kits by providing useful diagnostic information. Furthermore, the algorithm could be ported to a mobile platform to make it particularly helpful in remote rural health monitoring.
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