Diagnosis at the molecular level: analytical laser spectroscopy for clinical applications

Abstract

Diagnosis of disease conditions at present are mostly done from observation of symptoms produced after the disease has progressed to some extent. Though some techniques like X-ray mammography, PAP smear, and PSA test are available for screening purposes they are of limited application. Mammography, for example, cannot discriminate between benign and malignant conditions, and like all imaging methods will be useful only after the tumor has grown to detectable size. PAP smear is highly subjective and is prone to high false negative values. Optical methods and proteomics-based investigations are coming up as promising alternate / complementary approaches for early detection of many diseases, especially those which remain clinically silent for long periods, like cancer. Optical methods are extremely sensitive, can be automated, easily adaptable for in situ / in vivo applications and are highly objective since they can be mathematically processed to get statistically significant conclusions. They depend on the spectroscopic characteristics of the biomolecules in the system. The amounts, types, and functions of these molecules undergo drastic alterations during the onset, progression, regression, or recurrence of a disease. Optical methods are thus suitable for not only early detection, but also for monitoring of progression of disease, effect of therapy and any recurrence as soon as it happens. In this review we illustrate the present status of optical techniques for disease diagnosis with results from Roman, and fluorescence spectroscopy studies on tissue samples, and proteomics studies on body fluids like blood, saliva, cervical wash, and tissue homogenates.