CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Sang-Ho Jo, MD,
Bon-Kwon Koo, MD, PhD,
Tae-Jin Youn, MD, PhD and
Hyo-Soo Kim, MD, PhD*
* Division of Cardiology, Department of Internal Medicine, Seoul National University, College of Medicine, Cardiovascular Center, 28 Yongon-dong Jongno-gu, Seoul 110-744, Korea (Email: hyosoo{at}snu.ac.kr).
We thank Dr. Deray and Dr. Persson and colleagues for giving us an opportunity to clarify the reason behind sample size discrepancy between published RECOVER (Renal Toxicity Evaluation and Comparison Between Visipaque [Iodixanol] and Hexabrix [Ioxaglate] in Patients With Renal Insufficiency Undergoing Coronary Angiography) and abstracts presented in scientific meetings (1–3) and to explain some issues.
Persson et al. (4) reported the finding of iodixanol inferiority contrary to that of the RECOVER study. However, the study by Persson et al. (4) was a retrospective study that had many compounding factors influencing results. The researchers did not present the basal serum creatinine and contrast dose of all patients, and the baseline characteristics of study groups were significantly different. Most importantly, previous renal failure, prior dialysis, ST-segment elevation myocardial infarction (STEMI), and unstable coronary diseases were more frequent in the iodixanol group, all of which were very critical determinants in developing contrast-induced nephropathy (CIN) and affecting clinical outcomes. We do not agree with Persson et al. (4) because of these critical limitations.
We showed a trend of lower CIN incidence in iodixanol by the more stringent criteria (serum creatinine increase  0.5 mg/dl) as in the NEPHRIC (Nephrotoxicity in High-Risk Patients Study of Iso-Osmolar and Low-Osmolar Non-Ionic Contrast Media) (5) despite failure to reach statistical significance (3.6% vs. 8.9%, p = 0.067). We disagree with the view of Dr. Persson and colleagues that iso-osmolar contrast media had no beneficial effect over low-osmolar contrast media owing to a p value of 0.067. Other investigations support the superiority of iodixanol, such as Chalmers’ study, the NEPHRIC study, and recent meta-analyses (6,7).
Regarding the different sample size, only preliminary data of the RECOVER study were shown in scientific meetings, and registry data collected during the same period that the RECOVER study was conducted were erroneously incorporated into randomization data. Therefore, the iodixanol group was asymmetrically larger, and total patient population was higher in abstracts of scientific meetings.
We agree with Dr. Deray’s comment that it would be better to present both intention-to-treat and per-protocol analyses. However, many investigators presented their data only by per-protocol analysis (8). Moreover, both analyses made no differences in the RECOVER trial.
We already addressed the issues regarding different age and similar clinical outcomes of our study. Some studies reported age over 75 as the risk factor of CIN (9). In the RECOVER study, the mean age of both groups was under 75 years, and the proportion of patients over 75 was 18% in the iodixanol group and 22% in the ioxaglate group, with no difference (p = 0.451). We do not believe that the age difference influenced our results.
Finally, all patients in the RECOVER study received adequate periprocedural hydration, and the body weight was similar in the 2 groups, as depicted in the study. Although the exact level of hydration was only available in some patients, volume status was evaluated by both physical examination and laboratory test in all patients. Thereafter, dehydrated and acute renal-failure patients were excluded.
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References
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1. Jo SH, Youn TJ, Koo BK, et al. Renal toxicity evaluation and comparison between Visipaque (iodixanol) and Hexabrix (ioxaglate) in patients with renal insufficiency undergoing coronary angiography: the RECOVER study: a randomized controlled trial J Am Coll Cardiol 2006;48:924-930.[Abstract/Free Full Text]2. Jo SH, Youn TJ, Park JS, et al. Iodixanol is less nephrotoxic than ioxaglate in patients with renal insufficiency after coronary angiography(abstr) J Am Coll Cardiol 2005;45(Suppl A):32A. 3. Jo SH, Youn TJ, Koo BK, et al. Renal toxicity evaluation and comparison between Visipaque (iodixanol) and Hexabrix (ioxaglate) in coronary angiography in renal insufficiency—RECOVER trial. 2005Paper presented at: European Society of Cardiology Annual Congress; September 3–7; Stockholm, Sweden. 4. Liss P, Persson PB, Hansell P, et al. Renal failure in 57,925 patients undergoing coronary procedures using iso-osmolar or low-osmolar contrast media Kidney Int 2006;70:1811-1817.[CrossRef][Web of Science][Medline] 5. Aspelin P, Aubry P, Fransson SG, et al. Nephrotoxic effects in high-risk patients undergoing angiography N Engl J Med 2003;348:491-499.[CrossRef][Web of Science][Medline] 6. Chalmers N, Jackson RW. Comparison of iodixanol and iohexol in renal impairment Br J Radiol 1999;72:701-703.[Abstract] 7. McCullough PA, Bertrand ME, Brinker JA, Stacul F. A meta-analysis of the renal safety of isosmolar iodixanol compared with low-osmolar contrast media J Am Coll Cardiol 2006;48:692-699.[Abstract/Free Full Text] 8. Merten GJ, Burgess WP, Gray LV, et al. Prevention of contrast-induced nephropathy with sodium bicarbonate: a randomized controlled trial JAMA 2004;291:2328-2334.[Abstract/Free Full Text] 9. Mehran R, Aymong ED, Nikolsky E, et al. A simple risk score for prediction of contrast-induced nephropathy after percutaneous coronary intervention: development and initial validation J Am Coll Cardiol 2004;44:1393-1399.[Abstract/Free Full Text]
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