Visipaque (iodixanol) and hexabrix (ioxaglate) in renal insufficiency.

I read with great interest the RECOVER (Renal Toxicity Evaluation and Comparison Between Visipaque and Hexabrix in Patients With Renal Insufficiency Undergoing Coronary Angiography) study by Jo et al. (1). They compared the renal tolerance of iodixanol and ioxaglate in patients with renal insufficiency after coronary angiography. They found that the incidence of contrastinduced nephropathy (CIN) was lower in the iodixanol group (7.9%) as compared with the ioxaglate group (17%) (p 0.021). I would be interested in obtaining some details as to why substantial differences exist in the number of patients presented in different meetings (n 281) (2,3) and in the final publication (n 275). In this regard, I also do not understand how 164 and 117 patients for the iodixanol and the ioxaglate groups, respectively, may have been presented in previous meetings while the plan’s sample size was 150 patients in each group with a permuted block-randomization method. Also, an intention-to-treat analysis would seem more appropriate than a per-protocol analysis. Furthermore, among risk factors that might have influenced the results, age (4) and hydration status (5,6) are crucial. Patients were older in the ioxaglate group (68.7 7.5 years vs. 66.1 8.6 years; p 0.01). Although the investigators indicate that the difference is likely to be too small to be relevant it may still represent a bias that may explain at least partially their results. Volume supplementation remains the cornerstone for the prevention of CIN. Hydration status was not assessed and/or not presented. Body weight, diuresis, and volume given to the patients should be indicated to ensure comparability between groups. Finally, CIN remains a major health issue. Only one study (7) has shown in diabetic patients with renal insufficiency that iodixanol is less nephrotoxic than iohexol. Further trials should be conducted to assess the comparative renal tolerance of low osmolar contrast media (both ionic and nonionic) and nonionic dimers.