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Loma Linda University Medical Center Loma Linda, CA 92354

 
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We thank Dr. Karlik for his careful analysis of our article on gadodiamide-associated nephrogenic systemic fibrosis. He asked for clarification of our data regarding the prevalence of nephrogenic systemic fibrosis on a per patient basis. In the original article we chose to present the data in a 2 x 2 contingency table, counting the number of MRI examinations (contrast-enhanced and unenhanced examinations) and the number of examinations either resulting in nephrogenic systemic fibrosis or not resulting in nephrogenic systemic fibrosis. We chose this approach because the patients often underwent multiple MRI examinations during the period 2000–2006. Some of the patients in whom nephrogenic systemic fibrosis developed had undergone previous MRI examinations that did not lead to the development of nephrogenic systemic fibrosis. To calculate the odds ratio and likelihood ratio, we also had to count the number of unenhanced MRI examinations to exclude the remote possibility that nephrogenic systemic fibrosis could be caused by a factor related to the MRI examination other than gadodiamide exposure.

On further review of our database, we did find one error in the number of dialysis patients in the results section of the article. The 559 MRI examinations were performed on 238 dialysis patients rather than 168 patients as originally reported. The 301 gadodiamide-enhanced MRI examinations were performed on 168 patients. The other 70 dialysis patients underwent only unenhanced MRI examinations. This error in reporting the number of patients does not affect the calculated odds ratio, likelihood ratio, or prevalence because these values were calculated on the basis of the number of MRI examinations. In our study the prevalence of nephrogenic systemic fibrosis among gadodiamide-exposed dialysis patients was 12/301, or 4.0% per examination. The prevalence per patient would be 12/168, or 7.1%. It is interesting to note that our reported prevalence of 4.0% is quite similar to the 4.6% 1-year incidence of nephrogenic systemic fibrosis recently found by Sadowski et al. [1].

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1. Sadowski EA, Bennett LK, Chan MR, et al. Nephrogenic systemic fibrosis: risk factors and incidence estimation. Radiology 2007;10.1148 Jan31; [Epub ahead of print]

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This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Broome, D. R. Articles by Girguis, M. S. Search for Related Content PubMed Articles by Broome, D. R. Articles by Girguis, M. S. Social Bookmarking                      What's this?