The article, “Establishing Reference Intervals for Gadolinium Concentrations in Blood, Plasma, and Urine in Individuals Not Previously Exposed to Gadolinium-Based Contrast Agents” by Layne et al., was published in Investigative Radiology earlier this year. Their study set out to determine whether healthy people who have never received a gadolinium-based contrast agent (GBCA) have detectable concentrations of gadolinium (Gd) in their blood and urine, and to then develop a reference range for Gd concentrations in blood and spot urine. A secondary aim of the study was to determine whether spot urine Gd concentrations are equivalent to those in timed 24-hour urine collections.  In the majority (93.3%) of their 120 healthy volunteers, the Gd concentrations were undetectable in blood, plasma, spot urine samples, and 24-hour urine collections. No participants had detectable concentrations of Gd in their plasma. The authors noted that those subjects who did have detectable Gd concentrations in their spot urine samples had considerably lower concentrations than those identified in the reference interval published on the Mayo Clinic web site, which is less than 0.8 mcg/g creatinine.

Proposed Gadolinium Reference Intervals, Layne et al. (2020):

• • • Whole blood: <0.008 ng/mL or <0.050 nmol/L
    • Plasma: <0.009 ng/mL or <0.057 nmol/L
    • Spot urine: <0.036 μg/g creatinine or <0.0250 nmol/mmol

More Study Details –

Twenty subjects also did a timed 24-hour urine collection, and urine Gd concentrations were measured in samples from those collections. None of the 24-hour urine collections had detectable Gd concentrations, and those 20 subjects also did not have detectable Gd in their spot urine specimens.

Study participants were recruited from the staff at Guy’s and St Thomas’ NHS Foundation Trust, London, and students from King’s College London who are based at St Thomas’ Hospital. Potential subjects completed a basic health questionnaire to determine suitability for inclusion in the study. Participants had to be 18 years or older with no significant medical history, no history of smoking or vaping within the previous 6 months, and no prior exposure to gadolinium or GBCAs.  All participants had an estimated glomerular filtration rate (eGFR) of 70 or greater.  Of the 120 subjects, 79 (65.8%) were female and 41 (34.2%) were male.  The median age was 29.6 years.

Although no subjects reported having an MRI with a GBCA, detectable concentrations of Gd were found in 10 of the 120 subjects.  Four of those 10 reported undergoing an MRI without contrast in the past, which could not be confirmed, so those 4 were excluded from further data analysis.

The authors noted that it is possible that subjects had a degree of background Gd exposure from anthropogenic gadolinium which is known to be in tap water. (more…)