Low-Cost Refractometer for Measurement of Protein Concentration and Specific Gravity of Body Fluids

Abstract

The measurement of protein concentration in serum and other body fluids can be helpful in disease diagnosis and prognosis. It is commonly helpful to know whether a collection of fluid is transudate or exudate. The specific gravity of fluids, including urine, can also be a useful diagnostic tool. The estimation of protein concentration is usually possible only in hospitals where costly chemistry analysers are available. Specific gravity can be measured by standard methods only if large volumes of fluid are available: it is often not possible to measure the specific gravity of cerebrospinal, pleural, pericardial, or pancreatic fluids, or of urine if the volume is less than 50 μl. Recently, we have obtained a small and very handy device by which one can measure both the specific gravity of fluids in small volumes and also their protein content. The method is based on the refraction of light. Both purchase and running costs are very low by comparison with standard laboratory techniques. We describe the use of this instrument and compare its performance with other available methods.