Sorted By Test Name - Mayo Medical Laboratories

SGBF
8275
SGU
9318
SPCID
82971
Clinical References: Standards for Blood Banks and transfusion Services. 21st edition. AABB, 2002
Specific Gravity, Body Fluid
Clinical Information: Specific gravity (SG), the ration of the mass of a solution compared to the
mass of an equal volume of water, is an estimate of the concentration of substances dissolved in the
solution. Accessing whether a body fluid specimen is exudative or transudative in nature is the initial step
in determining the etiology of the fluid. Transudative fluids result from hemodynamic aberrations or
oncotic changes and are associated with ultrafiltration of serum across membranes. Transudates most
commonly occur in association with clinically apparent conditions such as heart failure and cirrhosis.
Exudative fluids tend to develop as a consequence of inflammation or malignant disorders such as
tuberculosis, pneumonia or cancer, in which capillary permeability is increased, allowing large-molecularweight
compounds to be released into the accumulating fluid. If the fluid is transudate, further diagnostic
procedures are often not necessary, however the presence of an exudative fluid often triggers additional
testing that may be invasive in nature. Determination of body fluid SG can aid in the distinction between
transudative and an exudative fluid. SG in exudates is greater than in transudates. This same information
can be obtained from the total protein using 3 g/dL as the cutoff.
Useful For: An aid in determining the type of body fluid: exudate vs transudate
Interpretation: Exudate fluid SG is >1.015; transudate fluid SG is