Detection of changes in mortality after heart surgery

BMJ 1998;317:1453 ( 21 November )

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Detection of changes in mortality after heart surgery

Control limits failed to account for case mix

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Control limits failed to account for case mix

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EDITOR $---$ We are concerned about the graphical technique described by Poloniecki et al in their analysis of perioperative mortalityrates associated with cardiac surgery.¹ Figure 2 shows threetraces: observed mortality performance bracketed by control limitsand plotted against the number of successive cases performed.The interpretation of the middle of the traces is straightforwardsince it is simply a variable life adjusted display that has previouslybeen described and will be familiar to many cardiac surgeons inthe United Kingdom.² The use of control limits, on the otherhand, is new. However, the usefulness and indeed the validityof these is not clear. As the authors themselves note, their analysisdoes not amount to a formal test of significance since the controllimits have not been corrected for multiple testing; this is amajor deficiency. The use of 99% control limits rather than 95%control limits presumably increases their . . . [Full text of this article]

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Cumulative risk adjusted mortality chart for detecting changes in death rate: observational study of heart surgery: J Poloniecki, O Valencia, and P Littlejohns
BMJ 1998 316: 1697-1700. [Abstract] [Full Text] [PDF]

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