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Dialysis |
Division of Nephrology, Veterans Affairs North Texas Health Care System and University of Texas Southwestern Medical Center at Dallas, Dallas, Texas
Correspondence: Dr. Robert F. Reilly, VA North Texas Health Care System, Section of Nephrology, Mail code 111G1, 4500 S. Lancaster Road, Dallas, TX 75216. Phone: 214-857-1907; Fax: 214-857-1514; E-mail: robert.reilly2{at}va.gov
| Abstract |
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Design, setting, participants, & objectives: Appointment logs were used to generate a database of all long-term hemodialysis patients at the Dallas Veterans Affairs hospital since August 2001. These patients were then examined in the Veterans Affair's electronic medical record system for gadolinium exposure during magnetic resonance imaging from 2000 through 2007, a period during which gadoteridol was the sole contrast agent used.
Results: A total of 141 patients were identified with 198 gadoteridol exposures. No cases of nephrogenic systemic fibrosis were identified. The observed frequency of nephrogenic systemic fibrosis was compared with the expected frequency (2.4%) using one-way
2 and binomial analysis, yielding a P < 0.05, indicating that the result was not explained by chance alone.
Conclusions: It is concluded that the risk for nephrogenic systemic fibrosis with gadoteridol in patients who are on long-term hemodialysis may be lower than with gadodiamide and gadopentetate dimeglumine.
| Introduction |
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Gadolinium has seven unpaired electrons in its outer shell and as a result is strongly paramagnetic and an ideal contrast agent for MRI. Free gadolinium, however, is highly toxic and relatively insoluble in water and as a result must be chelated to be used in humans. Each of the five FDA-approved GCC contains a unique chelate, as well as differing amounts of free chelate. The chelates may be either ionic or nonionic and either linear or cyclic. In general, ionic chelates tend to bind gadolinium more avidly than nonionic chelates. In addition, cyclic chelates bind gadolinium more strongly than linear chelates. If the pathophysiologic mechanism of NSF is related to gadolinium release, deposition, or binding in tissues, then one can make inferences regarding the potential risk of each GCC given their thermodynamic stability constants, dissociation half-lives, and the relative amount of free chelate in each preparation (Table 1). Chelates that bind gadolinium more avidly as evidenced by a higher thermodynamic stability constant and longer dissociation half-life or that contain more excess free chelate to scavenge released gadolinium might be associated with a lower NSF risk. Gadodiamide (Omniscan, GE Healthcare, Waukesha, WI) contains a linear nonionic chelate and has a very short dissociation half life (30 s). Gadopentetate dimeglumine (Magnevist, Bayer HealthCare Pharmaceuticals, Montville, NJ) has a linear ionic chelate and as a result has an intermediate dissociation half-life (10 min). The chelating molecule in gadoteridol (ProHance, Bracco Diagnostics, Inc., Princeton, NJ) is cyclic and nonionic and has the longest dissociation half-life (3 h) of any of the FDA-approved GCC.
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| Materials and Methods |
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Statistical Analyses
The observed versus expected rates of NSF were compared using one-way
2 with 1 df and binomial analysis. Standard descriptive statistics such as mean and SD were used to describe data collected when appropriate. The t test for two independent sample means was used to compare the means for the number of gadolinium exposures in MedWatch-reported cases of NSF with gadopentetate dimeglumine and gadodiamide.
| Results |
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2 with 1 df and binomial analysis. Both tests yielded a P < 0.05, indicating that the result was not explained by chance alone. Data were also obtained from the FDA's MedWatch through a freedom-of-information request. It should be cautioned that data from MedWatch are incomplete given that volunteer case reports are not subject to peer review and documentation is less stringent than in the published literature; as a result, conclusions drawn from MedWatch should be viewed with caution. Several interesting observations emerge from the individual reports as of October 23, 2007 (Table 4). The majority of reported associations are with gadodiamide (Omniscan), and in 246 of 283 gadodiamide-associated cases, gadodiamide was the only GCC administered. Gadopentetate dimeglumine (Magnevist) was the second most frequent GCC associated with NSF, and in 96 of 125 gadopentetate dimeglumine-associated cases, it was the sole GCC reported. When compared with other GCC-associated cases, for those that were associated with gadopentetate dimeglumine, the patient received that agent more frequently than gadodiamide (2.7 ± 2.43 versus 1.28 ± 1.07, respectively). This was statistically significant using the t test for unpaired samples. Although gadoversetamide (OptiMARK, Covidien, Hazelwood, MO) was less frequently associated, it is concerning that in eight of 20 reports, gadoversetamide was the sole GCC administered. Gadoteridol (ProHance) and gadobenate dimeglumine (MultiHance, Bracco Diagnostics, Inc., Princeton, NJ) were associated with nine and 10 cases, respectively. In only two of 10 cases associated with gadobenate dimeglumine was it the sole GCC administered. Of the nine cases of NSF associated with gadoteridol, in only one was it the sole GCC administered, and that patient received five doses during a 2-yr period (11).
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| Discussion |
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The vast majority of reported NSF cases (93 of 117) are associated with gadodiamide, and the American College of Radiology recommends that gadodiamide not be used in patients with renal disease (12). Gadopentetate dimeglumine makes up most of the remainder of reported cases (18 of 117), and recently it was recommended by the UK Medicine and Healthcare Products Regulatory Agency that patients with kidney disease not be administered this agent as well (14). Manufacturers websites and MedWatch report cases of affected patients, but these data are difficult to interpret without knowledge of market share for each of the five FDA-approved GCC. To date, 408 cases of NSF associated with GCC have been reported to MedWatch. Of these 408, 353 were associated with reporting of only one gadolinium preparation and 55 occurred when the patient was reported to be exposed to multiple preparations. At least 29.4% of patients received more than one gadolinium exposure. This may be an underestimation as a result of the way in which cases are reported. In the study by Deo et al. (8), three patients developed NSF (two with gadodiamide and one with gadopentetate dimeglumine) after a total of 123 gadolinium exposures; however, the number of patients who were exposed to each individual agent was not reported.
One would predict that gadodiamide (Omniscan) and gadoversetamide (OptiMARK), given their linear, nonionic chelate and similar thermodynamic stability constants (16.8), would be most likely to release gadolinium from the chelate and, therefore, be associated with the highest NSF risk. Gadodiamide has a dissociation half-life of only 30 s. The published literature and MedWatch data support an association for gadodiamide; however, there are no reported cases in the literature for gadoversetamide, and only 20 cases were reported to MedWatch. It is interesting that a high percentage of these 20 cases occurred with reporting of gadoversetamide exposure alone (40%). The difference in the number of reported cases between these two GCC has several possible explanations, including but not limited to the following: (1) The increased amount of free chelate in gadoversetamide (28.4 versus 14 mg/ml with gadodiamide) scavenges free gadolinium released from the chelate and is associated with a lower NSF risk; or (2) NSF risk with these agents is similar but differences in case reports and MedWatch reporting are due to differences in market share. Although exact US and worldwide market share data are difficult to obtain, within the VA between July 1, 2005, and September 30, 2007, gadodiamide had a larger market share than gadoversetamide: 25.6 and 6.1%, respectively (15). As a surrogate for the US market share, we used the VA purchasing records for GCC. The VA does not have a national contract for the purchase of GCC, and each individual VA hospital determines which GCC it purchases similar to that of non-VA hospitals across the country.
Gadopentetate dimeglumine (Magnevist) and gadobenate dimeglumine (MultiHance) contain linear ionic chelates. They have higher thermodynamic stability constants (22.2 and 22.6, respectively) than either gadodiamide (Omniscan) or gadoversetamide (OptiMARK). The dissociation half-life of gadopentetate dimeglumine is 10 min, and that for gadobenate dimeglumine has not been reported. A total of 30.6% of NSF cases that were reported to MedWatch were associated with gadopentetate dimeglumine. In 97 of 125 MedWatch cases that were associated with gadopentetate dimeglumine, it was the sole gadolinium-containing chelate administered. In 54.6% of these 97 cases, the patient received multiple doses. The interval during which this occurred is unclear because of the incompleteness of MedWatch reporting, and MedWatch data may also underrepresent the number of patients who received multiple doses. At least one study has linked the size of the gadolinium dose administered to the relative risk for association with NSF (4). One can extrapolate that the number of exposures and the period of time during which they occur may also affect the association. Whether this is particularly true of cases that are associated with gadopentetate dimeglumine remains to be determined. As shown in Table 4, the number of gadopentetate dimeglumine exposures per patient in MedWatch cases was higher (2.7 ± 2.43) than with any of the other four FDA-approved GCC. Gadobenate dimeglumine is associated with no case reports of NSF, and only 10 cases were reported to MedWatch. In only two of these 10 cases was gadobenate dimeglumine the sole GCC administered. Whether these dramatic differences in NSF association are confounded by market share or result from differences in other physicochemical properties is unclear. Within the VA between July 1, 2005, and September 30, 2007, gadopentetate dimeglumine had a much larger market share than gadobenate dimeglumine (53.9 and 3.2%, respectively) (15). The company websites for each agent list the number of administered doses worldwide as greater than 80 million for gadopentetate dimeglumine and 3.5 million for gadobenate dimeglumine (16,17).
Gadoteridol (ProHance) contains a cyclic nonionic chelate. It has the highest thermodynamic stability constant (23.8) and the longest dissociation half-life (3 h) of the five FDA-approved GCC. One might, therefore, predict that given these properties, it would be associated with the lowest NSF risk. Gadoteridol is associated with the fewest number of reported MedWatch cases (nine). It is interesting that of these cases, only one occurred with gadoteridol administered alone, and that patient had six exposures during a 2-yr period. There are no case reports to date linking NSF to gadoteridol exposure. It is possible, although less likely, that the low number of MedWatch cases and lack of reported cases are related to market share. Within the VA from September 1, 2005, to September 30, 2007, gadoteridol use was 11.1% of all GCC. The manufacturer's website indicates that more than 8.5 million doses of gadoteridol have been administered worldwide (18). In our study, we did not detect a case of NSF with 198 exposures. Given that no cases were detected, an exact incidence rate cannot be calculated, but we found that the number of cases detected was statistically significantly different from that of Deo et al. (8).
Given the nature of the study, it is possible that milder presentations of NSF were missed. Whether milder phenotypes of NSF are present is unclear and was suggested by one group (19). Hopefully, biopsies of exposed patients with suspected disease can be compared with controls with exacerbating and remitting edema from intermittent volume overload to address this issue more definitively in hemodialysis patients. It is also possible that some full-blown cases of NSF may have been missed by clinicians. Alternatively, a less likely explanation is that other risk factors associated with NSF, such as edema, endothelial damage, and liver disease, were underrepresented in our inner-city, hospital-based dialysis unit.
| Conclusions |
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2 and binomial analyses. Both tests yielded a P < 0.05, indicating that the result was not explained by chance alone. We conclude that NSF risk in patients who have ESRD and are on long-term hemodialysis may be lower with gadoteridol (ProHance) than with gadodiamide (Omniscan) and gadopentetate dimeglumine (Magnevist). Further studies will be required to confirm this finding and better delineate NSF risk with different gadolinium preparations. | Disclosures |
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| Acknowledgments |
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Parts of these data were presented in abstract form at the annual meeting of the American Society of Nephrology; November 2 through 5, 2007; San Francisco, CA.
| Footnotes |
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See related editorial, "How Should Nephrologists Approach Gadolinium-based Contrast Imaging in Patients with Kidney Disease?" on pages 649–651.
Received December 26, 2007. Accepted January 22, 2008.
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