Facts:
(1) The RBC volume in a healthy adult is 35.7 mL per kg lean body weight.
(2) The specific gravity of RBC is 1.094 g/mL (see above).
Parameters:
(1) actual body weight
(2) percent body fat as a decimal fraction
(3) measured (observed) total red cell volume in mL
If the line in Figure 1 is analyzed, the following equation is derived:
normal total RBC volume in mL per kg body weight at a given amount of body fat =
= 35.22 - (33 * (decimal fraction for body fat))
The corresponding equation according to the text appears to be:
normal total RBC volume in mL per kg body weight at a given amount of body fat =
= 35.7 - (34 * (decimal fraction for body fat))
normal total RBC volume in mL for an expected fraction of body fat =
= (body weight in kg) * (total RBC volume)
ratio of measured to normal total RBC volume =
= (measured volume in mL) / (normal volume in mL)
Interpretation:
• If the ratio is > 1.2 (120%) then the patient is polycythemia.
