Described herein is an apparatus and method for generating a pain score for a patient. The method includes the steps of generating a PLR response signature for each drug of a plurality of drugs and further initiating a light stimulus to the patient, and measuring a corresponding PLR response. The method includes initiating a neuro-stimulus to the patient, the neuro-stimulus being initiated over a set of frequencies, each frequency being associated with a unique intensity, and stimulating a unique nerve fiber type of the patient, and measuring a PRD response of the patient for the initiated neuro-stimulus. Further, the method includes determining, for each nerve fiber type, a threshold response based on the measured PRD, determining a weight for each threshold response based on the PLR response, and combining the determined weight for each threshold response to obtain a pain score for the patient.