The present invention provides an apparatus and a method for identifying the risk of a clinical condition in a human or animal by correlating Near Infrared (NIR) absorbance spectral data with one or several parameters including a concentration of one or more substances in the skin, a concentration of one or more substances in skin plus subdermal tissue, a score derived from one or more clinical tests like a stress test on a treadmill, coronary angiography, or intravascular coronary ultrasound. The method determines the concentration of a compound in the skin of a human or animal and comprises the steps of placing a part of the skin against a receptor, directing electromagnetic radiation (EMR) from the near-infrared spectrum onto the skin, measuring a quantity of EMR reflected by, or transmitted through, the skin with a detector; and performing a quantitative mathematical analysis of the quantity of EMR to determine the concentration of the compound, for example free and esterfied cholesterol. An example of a clinical condition is cardiovascular disease.