Apparatus and method for spectroscopic analysis of tissue to detect diabetes in an individual

#The present invention generally relates to the field of diagnostic spectroscopy. More specifically, the present invention provides a method and apparatus for noninvasive rapid screening or diagnosis of diabetes in an individual by irradiating tissue with light comprising at least one wavelength greater than 500 nm and less than 3300 nm, collecting and measuring optical information from the tissue and applying multivariate techniques to the optical information to predict the probability of a subject having diabetes.

#In 1997, it was estimated that 15.7 million people in the United States had diabetes, of which about 10.3 million were diagnosed and 5.4 million were undiagnosed. Due to the American lifestyle of poor diet and being overweight, the incidence of diabetes is becoming of epidemic proportions. Type II diabetes accounts for 90 to 95% of all cases of diabetes in the Untied States, making it and its attendant clinical and economic consequences a major public health problem. While the prevalence of diabetes in the Unites States is about 5% of the population, care for diabetes accounts for about 15% of health care expenses.

#The chronic hyperglycemia of diabetes is associated with long-term damage, dysfunction, and failure of various organs, especially the eyes, kidneys, nerves, heart, and blood vessels. Most cases of type I diabetes are detected soon after symptoms develop, which is not the case for type II diabetes. Individuals with undiagnosed type II diabetes are at significantly higher risk for coronary heart disease, stroke, and peripheral vascular disease than the non-diabetic population. They also have a greater likelihood of having dyslipidemia, hypertension, and obesity. Early detection can reduce the burden of type II diabetes and its complications as well as lessen the economic consequences.

#FIG. 1 is a plot depicting the difference in mean spectra of a sample population of diabetic and non-diabetic individuals compared with the spectrum of collagen;

#FIG. 2 is a plot depicting discriminant distance between diabetics and nondiabetics in a set of collected spectral data;

#FIG. 3 is a plot depicting Mahalanobis distance for the data of FIG. 2;

#The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments that are not intended to limit the scope of the invention.

#Embodiments of the present invention include apparatus and methods useful for providing rapid, accurate diagnosis of diabetes without the incumbent drawbacks of the present fasting plasma glucose test or the oral glucose tolerance test. The methods and apparatus can also be used for screening diabetes, including type II diabetes, before it is clinically identifiable through other methods currently in use. The method can use near-infrared spectroscopy to non-invasively interrogate the tissue of the subject to detect the presence or progression of diabetes.

#The method, in one embodiment, includes the in vivo use of optical spectroscopy with wavenumbers in the region of 20,000 to 3000 cm−1 (wavelengths in the region of 500 to 3300 nm) to screen or diagnose type II diabetes mellitus. The optical information which may be processed in the form of spectra can be used to generate a predictor of disease using multivariate methods such as linear discriminant analysis, quadratic discriminant analysis, logistic regression, neural nets, and partial least squares regression. The method of discrimination is based in part on detecting evidence of elevated glucose as seen by the level of glycosylation end products preferably evidenced by glycosylated collagen (furosine) in the tissue analyzed.