methods for detecting disease in a patient are disclosed . the methods involve administering to the patient a quantum dot - analyte conjugate , which includes an analyte that binds to a marker for the disease in the patient &# 39 ; s gastrointestinal tract . the analyte is conjugated to a quantum dot having a characteristic emission wavelength . using an endoscopic modality , a physician can illuminate portions of the patient &# 39 ; s gastrointestinal tract and detect the presence of the marker based on emission of the quantum dot . also disclosed are methods of predicting a response to a treatment in a patient .