Evaluating non-randomised intervention studies - NIHR Health ...

Health Technology Assessment 2003; Vol. 7: No. 27TABLE 37 Dead or dependent at 6 months according to neurological deficit score (IST)Aspirin (n = 7749) No aspirin (n = 7753) OR (95% CI)Deficit score No. (% adverse outcomes) No. (% adverse outcomes)0 267 (43.8) 246 (39.8)1 719 (41.6) 767 (38.5)2 1373 (53.0) 1421 (51.4)3 2298 (63.4) 2252 (63.4)4 2028 (78.8) 2020 (77.7)5 861 (88.6) 843 (88.6) 1.64 (1.60 to 1.68) per unit increase in score6 203 (92.1) 204 (86.7)TABLE 38 Distribution of baseline characteristics by country (IST)Sample sizeAdverse outcome (%)Delay (h) (mean)Female (%)Age in (years) (mean)Systolic blood pressure (mean)Symptoms on waking (%)Drowsy or unconscious (%)Atrial fibrillation (%)Deficit score (mean)No CT scan (%)Partial anterior +Total anterior strokes (%)Australia 597 56 19 60 71 155 29 26 12 3.0 13 32 + 27 = 59Northern Italy 1911 55 17 52 72 162 31 20 20 3.1 28 39 + 22 = 61Central Italy 980 61 21 60 74 161 24 21 18 2.9 32 50 + 17 = 67Southern Italy 546 60 16 64 70 154 27 20 19 3.2 31 46 + 18 = 64The Netherlands 728 54 16 52 69 169 30 20 10 3.1 14 37 + 27 = 64New Zealand 453 51 25 51 72 155 28 19 17 3.0 4 37 + 22 = 59Norway 526 60 24 53 72 165 28 19 6 2.9 6 44 + 19 = 63Poland 759 53 18 51 69 163 34 28 25 3.3 49 44 + 19 = 63Spain 478 46 19 56 71 157 31 15 15 3.1 21 38 + 24 = 62Sweden 636 42 24 55 75 167 30 15 15 2.5 2 50 + 16 = 66Switzerland 1631 67 17 52 74 164 29 31 16 3.1 26 39 + 28 = 67Scotland 1043 75 23 50 72 158 27 25 21 3.2 46 39 + 29 = 68Northern England and Wales 2762 79 20 53 72 159 27 25 18 3.1 61 41 + 27 = 68Southern England 2452 81 22 51 76 159 27 28 24 3.3 61 40 + 30 = 70arm for the resampling to be undertaken. Inaddition, the sequential nature of the studyrecruitment was used to split participants into‘early recruits’ and ‘later recruits’ to enablehistorically controlled studies to be constructed.Early recruits were those recruited up to andincluding the 15 January 1995; late recruits werethose recruited after this date. This date waschosen to maximise the number of regionsavailable for inclusion in the study and is close tothe median recruitment date.To be considered as a sub-study for the concurrentcohort design, we required that there were at least100 participants within each arm of each trial. Forthe historical cohort design we required that whenthe arms were divided into early and late recruits,there were at least 100 early control recruits and100 late treatment recruits.Fourteen geographical regions were constructedon this basis for the main analysis for bothconcurrent cohort and historical cohort designs.169© Queen’s Printer and Controller of HMSO 2003. All rights reserved.