Systems and methods directed to a monoclonal antibody covalently conjugated to latex in a two-step process to be used with a test strip and mobile-phone connected fluorimeter device. The test strip is combined with a method of analysis for quantitative detection of NT pro-BNP using the mobile device. A method for NT-proBNP testing system includes reading the test at an initial time point and at specific intervals during development of the test result, the dynamic behavior of the test can be used to distinguish differences between samples that would otherwise be difficult to differentiate by an end-point measurement due to the hook effect. Using two fluorescent tags with different excitation wavelength or emission wavelengths, or two colored beads with different absorption wavelengths, the test and the control line can simultaneously be read as they develop and dynamic formation can be used to distinguish high levels.