Feasibility and impact of the measurement of extracellular fluid volume simultaneous with GFR by 125I-iothalamate

Clin J Am Soc Nephrol. 2008 Sep;3(5):1308-15. doi: 10.2215/CJN.05501207. Epub 2008 Jul 23.

Abstract

The feasibility, validity, and possible applications of the assessment of extracellular fluid volume (ECFV) simultaneous with glomerular filtration rate (GFR) were assessed in a series of validation studies using the constant infusion method of (125)I-iothalamate (IOT). In 48 subjects with a broad range of GFR, distribution volume (V(d)) of IOT corresponded well with V(d) bromide (16.71 +/- 3.0 and 16.73 +/- 3.2 l, respectively, not significant), with a strong correlation (r = 0.933, P < 0.01) and without systematic deviations. Reproducibility assessment in 25 healthy male subjects showed coefficients of variation of 8.6% of duplicate measurement of V(d) IOT during strictly standardized (50 mmol Na(+)/d) sodium intake. An increase in dietary sodium intake (200 mmol Na(+)/d) induced a corresponding rise in V(d) IOT of 1.11 +/- 1.5 l (P < 0.01). In 158 healthy prospective kidney donors, the impact of indexing of GFR to ECFV was analyzed. Age, gender, height, and body surface area (BSA) were determinants of GFR. Whereas GFR, GFR/BSA, and GFR/height were gender-dependent, GFR/ECFV was gender-independent and not related to height or BSA. This supports the potential of normalizing GFR by ECFV. Thus, ECFV can be simultaneously assessed with GFR by the constant infusion method using IOT. After appropriate validation, also other GFR tracers could be used for such a simultaneous estimation, providing a valuable resource of data on ECFV in renal studies and, moreover, allowing GFR to be indexed to the body fluid compartment it clears: the ECFV.

Publication types

  • Validation Study

MeSH terms

  • Adult
  • Age Factors
  • Body Height
  • Body Surface Area
  • Bromides
  • Calibration
  • Extracellular Fluid / metabolism*
  • Feasibility Studies
  • Female
  • Glomerular Filtration Rate*
  • Humans
  • Infusions, Parenteral
  • Iodine Radioisotopes
  • Iothalamic Acid* / administration & dosage
  • Iothalamic Acid* / pharmacokinetics
  • Kidney / metabolism*
  • Kidney Function Tests* / standards
  • Kidney Transplantation
  • Male
  • Middle Aged
  • Models, Biological
  • Radiopharmaceuticals* / administration & dosage
  • Radiopharmaceuticals* / pharmacokinetics
  • Reproducibility of Results
  • Sex Factors
  • Sodium Chloride, Dietary / metabolism
  • Tissue Donors

Substances

  • Bromides
  • Iodine Radioisotopes
  • Radiopharmaceuticals
  • Sodium Chloride, Dietary
  • Iothalamic Acid