CPT® Code 84315

The CPT® Code 84315 refers to the measurement of specific gravity, which is a critical laboratory test used to assess the density of a body fluid, excluding urine. Specific gravity is defined as the ratio of the density of a substance to the density of a reference substance, typically water. A particle exhibiting a specific gravity of 1 is considered neutrally buoyant in water, meaning it neither sinks nor floats. When the specific gravity of a substance increases above 1, it indicates that the substance is denser than water, causing it to sink. Conversely, a specific gravity of less than 1 suggests that the substance is less dense than water, resulting in it floating. This measurement is particularly significant in clinical settings as it aids in differentiating between transudative and exudative fluids. Transudates, which are typically associated with systemic conditions such as heart failure and cirrhosis, have a lower specific gravity. In contrast, exudates, which arise from localized inflammatory processes or diseases such as tuberculosis, pneumonia, or cancer, exhibit a higher specific gravity. Therefore, determining the specific gravity of body fluids can provide valuable diagnostic information, guiding healthcare professionals in the evaluation and management of various medical conditions.