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Appendix 8TABLE 41 Baseline characteristics according to country (ECST)Sample sizeAdverse outcome (%)Female (%)Age (years) (mean)Previous major stroke (%)Neurological signs (%)Previous MI (%)Angina (%)Prophylactic aspirin use (%)>50% stenosis (%)Region 1 458 31 33 62 75 73 86 79 45 70Region 2 271 43 22 66 65 69 92 85 75 48Region 3 294 39 26 64 70 63 89 86 35 68Region 4 264 27 21 63 67 65 91 92 45 50Region 5 458 30 27 60 71 71 90 87 54 58Region 6 308 46 35 61 79 74 82 77 14 81Region 7 439 36 33 61 80 79 88 80 33 73Region 8 341 51 28 62 77 72 86 79 39 73MI, myocardial infarction.TABLE 42 Baseline characteristics according to country and recruitment period (ECST)Before (B) or after (A)Sample sizeAdverse outcome (%)Female (%)Age (years) (mean)Previous major stroke (%)Neurological signs (%)Previous MI (%)Angina (%)Prophylactic aspirin use (%)>50% stenosis (%)Region 1 B 131 45 36 60 75 31 10 15 41 54A 327 26 32 63 75 26 16 23 61 76Region 2 B 149 54 23 66 69 32 7 15 21 39A 122 30 21 67 61 30 10 15 29 60Region 3 B 119 49 29 63 76 34 10 8 71 60A 175 33 24 64 66 38 12 17 60 74Region 4 B 128 33 21 61 66 38 11 4 57 43A 136 22 21 64 68 32 7 13 54 57Region 5 B 243 39 26 59 70 30 13 13 38 48A 215 21 28 61 73 27 7 14 55 69Region 6 B 136 59 35 60 80 28 17 23 82 79A 172 37 35 62 77 24 18 23 90 82Region 7 B 201 55 35 61 81 18 14 23 56 70A 143 32 31 61 79 24 10 16 83 78172Region 8 B 231 53 25 62 73 34 13 22 48 73A 205 24 32 63 81 21 16 20 77 72
Health Technology Assessment 2003; Vol. 7: No. 27against smoking, treatment of raised bloodpressure and antiplatelet drugs, although itwas noted to vary between centres and over theyears.The primary outcome was death or major stroke.Overall there was a non-significant difference inoutcome (37.0% of surgery-group patients versus36.5% of control-group patients), although therewas a relationship between benefit of surgery anddegree of stenosis, surgery being of value when thedegree of stenosis was >80%.Baseline characteristics in the ECSTEight variables for baseline characteristicsassociated with prognosis were included in thedata set. Details of the values of these variables arenot given in the report as they will soon bepublished in other research publications producedby the trial collaborative group. Thesecharacteristics were collected during therandomisation process, and were thereforeavailable for every randomised patient.Adaptations made to the ECST for theresampling projectTo use the ECST dataset for this project, themulticentre nature of the trial was exploited toconstruct a series of smaller randomised and nonrandomisedstudies, in the same way as for theIST. Centres falling within geographical regionswere grouped together such that sufficientparticipants were accrued in each arm for theresampling to be undertaken. In addition, thesequential nature of the study recruitment wasused to split participants into ‘early recruits’ and‘later recruits’ to enable historically controlledstudies to be constructed. For all regions otherthan Region 4, early recruits were those recruitedup to and including 5 December 1987; laterecruits were those recruited after this date. A cutoffdate of 19 December 1988 was used for Region4. These dates were chosen to maximise thenumber of regions available for inclusion in thestudy.Sample sizes used in the resampling for the ECSTstudy were smaller than those for the IST. To beconsidered as a sub-study for the concurrentcohort design, we required that there were at least40 participants within each arm of each trial. Forthe historical cohort design we required that whenthe arms were divided into early and late recruitsthere were at least 40 early control recruits and 40late treatment recruits.Eight geographical regions were constructed onthis basis for the main analysis for both concurrentcohort and historical cohort designs. As centreswere smaller than for the IST, neighbouringcountries were grouped where necessary. Theseeight regions recruited 2833 (94%) of trialparticipants. For reasons of future publications,the regions are not identifiable in the tables wepresent.The ECST is one of two trials investigating theefficacy and safety of carotid endarterectomy.Both the ECST and the second trial, NASCET, 135published early results during the recruitmentperiod of the ECST, which led to the datamonitoring committee of the ECST changingthe inclusion criteria of the ECST in 1990.Cases recruited after this change were deletedfrom the data set where this change would beconfounded with the generation of groups(e.g. for the historically controlled studyanalyses).The distribution of the outcome of dead or majorstroke, and of the baseline characteristics in thesesub-studies are described in Table 41. Table 42describes the baseline characteristics for thecohorts split according to ‘early recruits’ (before)and ‘late recruits’ (after). Differences are evidentin both tables in the frequency of the outcome andfor some of the baseline characteristics, but aregreatest in the historical comparisons. In thesecentres the event rates are lower in the secondperiod in all eight centres, whereas thepercentages with high degrees of stenosis increasewith time in all but one centre. The patternobserved with degree of stenosis is likely to reflecta change in case-mix due to emerging evidence ofthe dangers of surgery for low-grade surgeryduring the trial’s recruitment period.173© Queen’s Printer and Controller of HMSO 2003. All rights reserved.
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Appendix 20 0 00Additional outcomes
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