Discussion

　　HUS/TTP used to be a rare disease in adults,with an estimatedfrequency of one case per million per year.In 50%of cases it wasassociated with pregnancy,malignant hypertension,HIV infection,cancer,or chemotherapy,and the remainderof caseswere familial orof unknown cause.In 1986 the first association of HUS/TTP withEcoliO157 infection was made and the incidence of the disorder hassince continued to rise in parallel with the global rise inE coliO157infections.After exposure toE coliO157,between 3%and 7%ofall patients progress to overt HUS/TTP.The incidence of HUS/TTPis highest in children and elderly people.

　　The course and prognosis of HUS/TTP differ substantiallybetween adults and children.Children with HUS develop acute renalfailure precipitately and the treatment of choice is dialysis,which isinitiated when the child becomes oliguric.Most children respond todialysis,and mortality rates of less than 5%are nowreported.In thecentral Scotland outbreak there were no deaths in children.Adultsseem to develop neurological or cardiovascular complications beforethe onset of oliguria.Neurological features are associated withincreased mortality,and neurological and cardiovascularcomplications of HUS/TTP were the most frequent causes of death inthe central Scotland outbreak.

　　Plasma exchange is an expensive(￡2500 per person treated inour hospital)and intensive procedure.Its effectiveness in thetreatment of HUS/TTP induced byE coliO157 needs to be showndefinitively in a multicentre,randomised controlled trial.However,for a disease with very high mortality and just one potentiallybeneficial treatment option,a trial thatwithholds this optionwould behard to justify.It would also be extremely difficult to organise sincecases ofE coliO157 occur sporadically.There will always be anunavoidable selection bias within such a trial,with patients who areexcluded from treatment because they have contraindications to TPEorwho die before treatment can be initiated.

　　If 5%of all cases ofEcoliO157 develop HUS/TTP,we wouldexpect about 40 adult cases of HUS/TTP per year in the UK(datafrom the Communicable Disease Surveillance Centre and ScottishCentre for Infection and Environmental Health).We suggest that anational register be established for adult cases of HUS/TTP,ascurrently operates for cases in children.This database would enablemonitoring of treatment and outcomes in adults,providing definitiveevidence of the effectiveness of TPEwithin about 5 years.

　　There is no evidence from our experience that TPE is harmful.

　　A national register of HUS/TTP secondary toE coliO157 coulddefine the role of TPE in the treatment of this serious disorder.

5　致谢(Acknowledgements)

　　这是指作者在论文写作过程中,对那些给予提供帮助、赞助、批评或建议的个人或单位表示谢意。在这一部分中,通常采用一般现在时,一句话概括出来。举例:

　　AcknowledgementsWe thank AK R Chaudhuri and W HWatson for their clinicalcontribution;the renal physicians and haematoligists at GlasgowRoyal Infirmary and Stobhill Hospital for clinical assistance in themanagement of cases;M Drummond for data collection;and theCentral ScotlandE coliO157 Research Group for the laboratorydatabase.

6　参考文献(References)

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