Abstract: The present invention provides methods for non-invasive spectroscopic measurement of the concentration of an electrolyte, such as, sodium, potassium, or calcium ion, in a subject's blood. In one embodiment of a method according to the invention, calibration spectra are obtained from a group of subjects having variable blood electrolyte concentrations, and simultaneously blood is drawn from these subjects for measuring reference electrolyte concentrations. Standard multivariate calibration methods are employed to develop one or more calibration equations, based on the calibration spectra and the reference measurements. These calibration equations can be employed to analyze spectra obtained from a new subject to non-invasively determine the concentration of the electrolyte of interest.

Abstract: A non-invasive spectral measurement for a target analyte present in a subject's tissue or blood derives spectral shapes corresponding to one or more human variability factors, such as, skin color, from spectra collected from a diverse calibration group of subjects. Another set of spectra are normalized based on the derived spectral shapes to generate a set of corrected spectra. The corrected spectra are then utilized to generate and/or enhance a calibration model for detecting and/or measuring the target analyte from one or more transderamlly obtained spectra of a subject.

Abstract: A non-invasive spectral measurement of a native, diagnostic or treatment component in blood or tissue, illuminates the back of the eye and collects return light that has passed through and been reflected from choroidal or retinal tissue. Spectral analysis detects a retinal tissue state, or detects the level of a blood or serum constituent, which may be a native constituent or a dye, marker or pharmacological agent. Time-resolved or spectral decay monitoring may be used to assess organ functioning, e.g., by administering a serum-carried indicator of uptake, clearance or binding rate for specific organs. Circulating cells or material diagnostic of different conditions may also be detected by spectral analysis, either directly, or by tagging with a suitable label.