title: (99m) Tc-labelled human serum albumin cannot replace (125) I-labelled human serum albumin to determine plasma volume in patients with liver disease.
abstract: OBJECTIVE
  Determination of plasma volume (PV) is important in several clinical situations. Thus, patients with liver disease often have augmented PV as part of their sodium-water retention. This study was undertaken to compare PV determination by two indicators: technetium-labelled human serum albumin ((99m) Tc-HSA) and iodine-labelled human serum albumin ((125) I-HSA), as the former may have advantages at repeated measurements and the latter is the classical gold standard.
  
  
  METHODS
  In 88 patients, (64 with liver disease, mainly cirrhosis, and 24 patients without liver disease), simultaneous measurements of PV were taken with (99m) Tc-HSA and (125) I-HSA after 1 h in the supine position. Blood samples were obtained before and 10 min after quantitative injection of the two indicators. In a subset of patients (n = 32), the measurements were repeated within 1 h.
  
  
  RESULTS
  In all patients, a close correlation was present between PV determined by the two indicators (r = 0·89, P<0·0001). In all, but twelve patients, a higher PV was obtained with (99m) Tc-HSA compared with (125) I-HSA (P<0·0001). PV determined with (99m) Tc-HSA exceeded PV determined with (125) I-HSA by 367 ml (5·2 ml kg(-1) ) in liver patients as compared to 260 ml (3·5 ml kg(-1) ) in patients without liver disease (P<0·05). The precision of repeated PV determination was 1·75% (coefficient of variation) with (99m) Tc-HSA and 1·71% with (125) I-HSA (ns), and similar values were found in patients with and without liver disease.
  
  
  CONCLUSIONS
  The study demonstrates that (99m) Tc-HSA has the same precision as that of (125) I-HSA. However, especially in patients with liver disease, (99m) Tc-HSA consistently overestimates the PV, most likely owing to indicator heterogeneity with subsequent fast removal from the circulating medium with a higher volume of distribution as the outcome.
authors.affiliation: Clinical Physiology and Nuclear Medicine 239, Center of Functional and Diagnostic Imaging and Research, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark. jens.h.henriksen@hvh.regionh.dk
authors.forename: Ulrik Lütken
authors.initials: UL
authors.lastname: Henriksen
authors.forename: Jens H
authors.initials: JH
authors.lastname: Henriksen
authors.forename: Flemming
authors.initials: F
authors.lastname: Bendtsen
authors.forename: Søren
authors.initials: S
authors.lastname: Møller
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001811:Blood Volume Determination / Q000379:methods*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D016014:Linear Models; D008107:Liver Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning; D010953:Plasma Volume; D011237:Predictive Value of Tests; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012711:Serum Albumin, Radio-Iodinated; D016683:Supine Position; D013668:Technetium Tc 99m Aggregated Albumin
chemical_list: D019275:Radiopharmaceuticals; D012711:Serum Albumin, Radio-Iodinated; D013668:Technetium Tc 99m Aggregated Albumin