The invention provides novel compounds, reagents, systems, and methods for detecting a metabolite related to a NRTI in a biological sample, and use thereof in monitoring adherence to pre-exposure prophylaxis or anti-retroviral treatment. Such reagents comprise NRTI derivatives, analogs, NRTI derivatives conjugates, along with antibodies directed to same, which are useful for antibody-based methods, such as a lateral flow immunoassay and other point of care devices.
