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VIII. ABOUT RESULTS
Conventional BIA uses regression equations to produce estimates of Total Body Water,
Extracellular Water, and Intracellular Water. Because equations are formulated based on normal
populations, accuracy of estimates may vary based on disparity between the subject and the
comparison population. In contrast, because the variables utilized by Bioelectrical Impedance
Vector Analysis (BIVA) - resistance and reactance - are directly determined by body fluid volume
and distribution, it is less affected by abnormal hydration.
16
How BIVA works
BIVA assesses fluid status and body cell mass through resistance (R) and reactance (Xc).
Assuming that resistance correlates with fluid, and reactance correlates with body cell mass, R
and Xc are normalized for height, and compared with the tolerance ellipses of the reference
population.
How to interpret a BIVA chart
The graphic display created by BIVA makes it easy to track changes in hydration status and body
cell mass, based on movement of the measurement point on the graph. Values located above the
long axis (/) indicate increased body cell mass (higher reactance), and values below the long axis
indicate decreased body cell mass (lower reactance). Values located above the short axis (\)
indicate less fluid/water (higher resistance), and values below the short axis indicate increased
fluid/water (lower resistance).
16. Bioelectrical impedance and body composition. Lancet, 340 (1992), p.1511
BIVA
Bioelectric Impedance Vector Analysis
-4
4
3
0
-2
-3
-4
95 %
Z(Xc)
Z(R)
75 %
50 %
-3
-2
0
2
3
4
More soft tissues
Less soft tissues
Less fluids
More fluids
-1
1
2
1
-1