CRD Summary: The authors concluded that N-acetylcysteine was more renoprotective than hydration alone for reducing risk of contrast-induced nephropathy; theophylline may also reduce risk. In spite of some methodological issues with the review, the authors' conclusions were still likely to be reliable.

[Eligible studies had to have one treatment group receiving N-acetylcysteine, theophylline, fenoldopam, iloprost, statin, dopamine, trimetazidine, bicarbonate, ascorbic acid, furosemide or mannitol.]

CRD Commentary: The review addressed a clear question and was supported by appropriate inclusion criteria. Attempts to identify relevant studies in five languages were undertaken by searching electronic databases and checking references. No search was made for unpublished data so this, coupled with the language restrictions, means that some relevant studies may have been missed. However, results from a funnel plot suggested publication bias was not a concern. Study quality was assessed and was used in interpreting the results of the review. Although suitable methods were used to minimise the risks of reviewer error and bias for the processes of study quality assessment and data extraction, only one reviewer selected studies for inclusion in the review, leaving this process open to such risks. Sufficient study details were provided and an appropriate meta-analysis of the data was undertaken. Although heterogeneity was assessed, its possible causes were not fully investigated or discussed. Many trials reported very few events, so a clear indication of the weight given to each study would have been useful in interpreting the pooling. The authors' conclusions nevertheless reflected the evidence available and were likely to be reliable.