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Should whole-body red cell mass be measured or calculated?
I Balga1, M Solenthaler, M Furlan
1Central Hematology Laboratory, University Hospital, Inselspital, Bern, Switzerland.
Blood Cells, Molecules & Diseases
|April 25, 2000
Summary
Accurate red cell mass (RCM) determination is crucial for diagnosing polycythemia vera. Calculating RCM from venous hematocrit and plasma volume is unreliable, leading to significant misclassifications in diagnosis.
Area of Science:
- Hematology
- Diagnostic Medicine
- Nuclear Medicine
Background:
- Accurate determination of whole-body red blood cell volume is essential for diagnosing polycythemia vera.
- Venous hematocrit may not accurately reflect the total red blood cell mass.
- Radioisotope labeling is the current standard for red cell mass (RCM) determination.
Purpose of the Study:
- To evaluate if red cell mass (RCM) can be reliably calculated from venous hematocrit and plasma volume, replacing radioisotope labeling.
- To assess the diagnostic accuracy of calculated RCM for polycythemia vera compared to measured RCM.
Main Methods:
- Retrospective study of 264 cases.
- Measured RCM using radioisotope labeling (51Cr or 99mTc).
- Estimated plasma volume using 125I-labeled albumin.
- Calculated RCM using an empirical factor (Ratio f) and venous hematocrit.
Main Results:
- Significant scattering of the empirical factor (Ratio f) ranged from 0.76 to 1.15 (mean 0.911).
- Calculated RCM values showed substantial differences from measured RCM.
- Using calculated RCM led to misclassification of 46 patients for polycythemia vera diagnosis.
Conclusions:
- The empirical factor (Ratio f) is too variable for accurate RCM calculation.
- Calculated RCM is not a reliable substitute for radioisotope-labeled RCM determination.
- Radioisotope labeling remains mandatory for precise whole-body red cell volume assessment in clinical practice.