A method for determining whether a sample is positive for an analyte, the method comprising: - collecting a plurality of background data points using a light detector, the background data points collected during a background time interval; - collecting a plurality of signal data points forming a luminescence signal using the light detector, wherein the plurality of signal data points is collected during a signal time interval that is after the background time interval, wherein the signal time interval includes a portion of time after the sample is activated by an activation reagent; - computing, by a computer system, a signal-to-background ratio using the plurality of background data points and the plurality of signal data points, wherein signal-to-background ratio is computed as a ratio of an area under the signal curve less the mean of the background, and the result is divided by a standard deviation of the background; - determining, by the computer system, a regression function that fits the plurality of signal data points, wherein the regression function includes at least a second order polynomial; - computing, by the computer system, an accuracy value of the regression function fitting the plurality of signal data points, wherein the regression function includes a parabolic coefficient of a second order term; - calculating, by the computer system, a score by adjusting an accuracy term with a signal-to-background term by subtraction or addition, wherein the accuracy term includes the accuracy value multiplied by the parabolic coefficient, and wherein the signal-to-background term is computed by multiplying the signal-to-background ratio by a reciprocal of a first constant; and - comparing the score to a classification threshold to determine a classification of whether the sample is positive or negative for the analyte. - collecting a plurality of background data points using a light detector, the background data points collected during a background time interval; - collecting a plurality of signal data points forming a luminescence signal using the light detector, wherein the plurality of signal data points is collected during a signal time interval that is after the background time interval, wherein the signal time interval includes a portion of time after the sample is activated by an activation reagent; - computing, by a computer system, a signal-to-background ratio using the plurality of background data points and the plurality of signal data points, wherein signal-to-background ratio is computed as a ratio of an area under the signal curve less the mean of the background, and the result is divided by a standard deviation of the background; - determining, by the computer system, a regression function that fits the plurality of signal data points, wherein the regression function includes at least a second order polynomial; - computing, by the computer system, an accuracy value of the regression function fitting the plurality of signal data points, wherein the regression function includes a parabolic coefficient of a second order term; - calculating, by the computer system, a score by adjusting an accuracy term with a signal-to-background term by subtraction or addition, wherein the accuracy term includes the accuracy value multiplied by the parabolic coefficient, and wherein the signal-to-background term is computed by multiplying the signal-to-background ratio by a reciprocal of a first constant; and - comparing the score to a classification threshold to determine a classification of whether the sample is positive or negative for the analyte.