99mTc-albumin can replace 125I-albumin to determine plasma volume repeatedly.
OBJECTIVE
Plasma volume assessment may be of importance in several disorders. The purpose of the present study was to compare the reliability of plasma volume measurements by technetium-labeled human serum albumin ((99m)Tc-HSA) with a simultaneously performed plasma volume determination with iodine-labeled human serum albumin ((125)I-HSA).


METHODS
In 15 healthy volunteers, simultaneous plasma volume measurements with (99m)Tc-HSA and (125)I-HSA were performed after ½ hour in the supine position. Blood samples were obtained 10, 15, 20, and 30 minutes after the injection for accurate retropolation from the plasma counts to time zero to correct for leakage of the isotopes from the circulation.


RESULTS
The mean difference (bias) between plasma volume measured with (125)I-albumin and (99m)Tc-albumin was 8 ml (0.1 ml/kg) with limits of agreement (bias ±1.96 SD) ranging from -181-196 ml (-2.3-2.5 ml/kg). The tracer disappearance rate was significantly higher with (99m)Tc-albumin (-23.1±7.1%/h) than with (125)I-albumin (-6.7±3.6%/h) (p <0.001).


CONCLUSIONS
This study demonstrates that (99m)Tc-HSA can replace (125)I-HSA for single measurements of plasma volume in healthy volunteers. It needs to be emphasized however, that repeated blood sampling for 1/2 hour after injection of the tracer is required to correct for the disappearance of (99m)Tc and (99m)Tc-HSA from the circulation.
Department of Clinical Physiology and Nuclear Medicine, Koege Hospital, Koege, Denmark. p_bonfi ls@post.tele.dk
Peter K
PK
Bonfils
Morten
M
Damgaard
Knud H
KH
Stokholm
Steen L
SL
Nielsen
D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010953:Plasma Volume / Q000502:physiology*; D019275:Radiopharmaceuticals / Q000097:blood* / Q000737:chemistry; D015203:Reproducibility of Results; D012711:Serum Albumin, Radio-Iodinated / Q000032:analysis / Q000737:chemistry*; D013668:Technetium Tc 99m Aggregated Albumin / Q000097:blood*
D019275:Radiopharmaceuticals; D012711:Serum Albumin, Radio-Iodinated; D013668:Technetium Tc 99m Aggregated Albumin