DETERMINING A CONCENTRATION OF A SUBSTANCE IN A SAMPLE USING A USABLE PORTION OF A SIGMOID CURVE

摘要

Techniques for calculating a concentration of a substance in a test sample are described that reduce variability in results. A sigmoid curve is generated from measurements of a metric for a reference sample having a known concentration of a substance. A usable portion of the sigmoid curve is determined using its second derivative. Measurements for a test sample that are within the usable portion are used to determine concentration of the substance in the test sample. A threshold value determined from the first derivative of the sigmoid curve is also applied to the test measurements to determine presence of the substance.