Table 4.

Strengths and limitations of GFR measurement methods and markers

ApproachStrengthsLimitations
Methods
    Urinary clearance
        Bladder catheter and continuous intravenous infusion of markerGold standard methodInvasive
        Spontaneous bladder emptyingPatient comfortPossibility of incomplete bladder emptying
Less invasiveLow flow rates in people with low levels of GFR
        Bolus administration of markerShorter durationRapidly declining plasma levels at high levels of GFR
Longer equilibration time in extracellular volume expansion
        24-h urinary collectionCan be performed at homeCumbersome
Prone to error
    Plasma clearanceNo urine collection neededOverestimation of GFR in extracellular volume expansion
Potential for increased precisionInaccurate values with one-sample technique, particularly at lower GFR levels
Longer duration of plasma sampling required for low GFR
    Nuclear imagingNo urine collection or repeated blood samples neededLess accurate
Relatively short duration
Markers
    InulinGold standardExpensive
No side effectsDifficult to dissolve and maintain into solution
Short supply
    CreatinineEndogenous marker, no need for administrationSecretion which can vary among and within individuals
Assay available in all clinical laboratories
    IothalamateInexpensiveProbable tubular secretion
Long half-lifeRequirement for storage, administration, and disposal of radioactive substances when125I used as tracer
Use of non-radioactive iothalamate requires expensive assay
Cannot be used in patients with allergies to iodine
    IohexolNot radioactivePossible tubular reabsorption or protein binding
InexpensiveUse of low doses requires expensive assay
Sensitive assay allows for low doseCannot be used in patients with allergies to iodine
Nephrotoxicity and risk for allergic reactions at high doses
    EDTAWidely available in EuropeProbable tubular reabsorption
Requirement for storage, administration, and disposal of radioactive substances when 51Cr is used as tracer
    DTPAWidely available in the United StatesRequirement for storage, administration, and disposal of radioactive substances when 99mTc used as tracer
New sensitive and easy to use assay for gadoliniumRequires standardization for 99mTc
Dissociation and protein binding of 99mTc
Concern for NSF when gadolinium is used as the tracer