Mortality control charts: Both components of POSSUM ratio require  critical analysis

doi:10.1136/bmj.326.7403.1397-a

BMJ 2003;326:1397 (21 June), doi:10.1136/bmj.326.7403.1397-a

Letter

Mortality control charts

Both components of POSSUM ratio require critical analysis

The first 150 words of the full text of this article appear below.

EDITOR—Mean mortality of almost 10% and 30% (max 50%)is reported for elective and emergency gastro-oesophageal surgeryin 29 units.¹ Yet none had underperformed. A benchmark isset even though institutions were not randomised.

A multifactorial model is created by using POSSUM to fit this dataset.² POSSUM's overpredicting tendency is compounded byduplication of identical risk factors. The control charts justifymortality for low workload when guidelines preclude small numbers.It is unclear if operative parameters comply with original definitions² and whether physiological scores incorporate resuscitation.In our institution, 70% of emergencies did not meet criteriabut resulted in an exaggerated POSSUM score.

A new formula based on prospective validated data is crucialin subspecialty subgroup analysis.³ Bias is inevitable iffew curative, palliative, oesophageal, and gastric cases, are combined when surgeons vary in their operability rates. It isunwise to compare a transhiatal oesophagectomy with a three. . . [Full text of this article]

George A Khoury, consultant surgeon

Conquest Hospital, East Sussex NHS Trust, St Leonards on Sea, TN37 7RD shw000@msn.com

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