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Table 1 Characteristics of included surrogate and final trials.

From: Treatment effect bias in randomised controlled trials using surrogate outcomes: a preliminary cohort study analysis

 

Surrogate Trials (N=138) N(%)

Final Trials (N=132) N(%)

Intervention clinical area

  

Cardiovascular

31(22)

31(23)

Endocrinology

11(8)

4(3)

Gastrology/hepatology

11(8)

11(8)

Infectious disease

28(20)

28(21)

Nephrology/urology

4(3)

4(3)

Neurology

2(1)

3(2)

Obstetrics

5(4)

5(4)

Oncology

4(3)

4(3)

Other

36(26)

36(27)

Pulmunology

6(4)

6(5)

Population clinical area

  

Cardiovascular

34(25)

31(23)

Endocrinology

14(10)

9(7)

Gastrology/hepatology

9(7)

10(8)

Infectious disease

21(15)

21(16)

Nephrology/urology

2(1)

5(4)

Neurology

2(1)

2(2)

Obstetrics

7(5)

8(6)

Oncology

4(3)

4(3)

Other

36(26)

36(27)

Pulmunology

9(7)

6(5)

Journal

  

Annals

14(10)

10(8)

BMJ

11(8)

14(11)

JAMA

31(22)

31(23)

Lancet

28(20)

28(21)

NEJM

51(37)

49(37)

PLoS

3(2)

-

Year

  

2005

64(46)

63(48)

2006

74(54)

69(52)

  1. Surrogate trials were less likely to have adequate evidence of randomisation sequence generation and adopt the ITT principle. We also found clear evidence that final trials were more likely to observe a non-statistically significant (‘neutral’) treatment effect than surrogate trials (49% vs 23%) (Table 2).
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