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Table 3 Design attributes of clinical trial within the ClinicalTrials.gov data set

From: A comparison of interventional clinical trials in rare versus non-rare diseases: an analysis of ClinicalTrials.gov

Characteristics

Rare disease trials* (n = 2759)

Non-rare disease trials* (n = 21329)

Difference in percentage points (rare –non-rare)

95% CI for difference

Number of facilities, n (%)

    
 

Single facility

1671 (61.3)

15443 (72.7)

−11.4

−9 to −13

 

2-3 facilities

333 (12.2)

2482 (11.7)

0.5

0 to 2

 

≥4 facilities

720 (26.4)

3315 (15.6)

10.8

9 to 13

Study phase, n (%)

    
 

Phase 0

15 (0.5)

166 (0.8)

−0.2

0 to −0.5

 

Phase 1

410 (14.8)

1848 (8.7)

6.2

5 to 8

 

Phase 1/2

294 (10.7)

1014 (4.8)

5.9

5 to 7

 

Phase 2

1212 (43.9)

4747 (22.3)

21.7

20 to 24

 

Phase 2/3

83 (3.0)

601 (2.8)

0.2

0 to 1

 

Phase 3

287 (10.4)

3110 (14.6)

−4.2

0 to −5

 

Phase 4

145 (5.3)

3398 (15.9)

−10.7

−10 to −12

 

NA

313 (11.3)

6445 (30.2)

−18.9

−17 to −20

Primary purpose, n (%)

    
 

Treatment

2451 (91.2)

16195 (79.3)

12.0

11 to 13

 

Prevention

87 (3.2)

1488 (7.3)

−4.0

−3 to −5

 

Screening

1 (0.0)

86 (0.4)

−0.4

−0.2 to −0.5

 

Supportive Care

39 (1.5)

844 (4.1)

−2.7

−2 to −3

 

Health Services Research

7 (0.3)

446 (2.2)

−2

−2 to −2

 

Educational/Counselling/Training

2 (0.1)

14 (0.1)

0.0

0 to 0

 

Diagnostic

75 (2.8)

917 (4.5)

−1.7

−1 to −2

 

Basic Science

25 (0.9)

441 (2.2)

−1.2

−1 to −2

Study has DMC†, n (%)

    
 

Yes

1211 (53.2)

7274 (40.9)

12.3

10 to 14

 

No

1066 (46.8)

10511 (59.1)

−12.3

−10 to −14

Intervention model¥, n (%)

    
 

Single Group Assignment

1691 (63.0)

6134 (29.6)

33.5

32 to 35

 

Parallel Assignment

837 (31.2)

12466 (60.1)

−28.9

−27 to −31

 

Crossover Assignment

140 (5.2)

1741 (8.4)

−3.2

0 to −4

 

Factorial Assignment

14 (0.5)

411 (2.0)

−1.5

−1 to −2

Intervention type‡, n (%)

    
 

Drug

2204 (79.9)

11891 (55.8)

24.1

22 to 26

 

Device

127 (4.6)

2620 (12.3)

−7.7

−7 to −9

 

Procedure

269 (9.7)

2408 (11.3)

−1.5

0 to −3

 

Biological

220 (8.0)

926 (4.3)

3.6

3 to 5

 

Radiation

112 (4.1)

476 (2.2)

1.8

1 to 3

 

Behavioural

47 (1.7)

2631 (12.3)

−10.6

−10 to −11

 

Dietary Supplement

31 (1.1)

562 (2.6)

−1.5

−1 to −2

 

Genetic

39 (1.4)

124 (0.6)

0.8

0 to 1

 

Other

176 (6.4)

2700 (12.7)

−6.3

−5 to −7

Allocation¥, n (%)

    
 

Randomised

949 (35.5)

14958 (71.6)

−36.1

−34 to −38

 

Non-randomised

1727 (64.5)

5937 (28.4)

36.1

34 to 38

Endpoint classification, n (%)

    
 

Efficacy Study

530 (22.0)

7454 (42.0)

−20.0

−18 to −22

 

Safety/Efficacy Study

1521 (63.2)

8148 (45.9)

17.3

15 to 19

 

Safety Study

276 (11.5)

1154 (6.5)

5.0

4 to 6

 

Pharmacodynamics Study

9 (0.4)

282 (1.6)

−1.2

−0.8 to −1.5

 

Pharmacokinetics Study

36 (1.5)

339 (1.9)

−0.4

0.2 to −0.9

 

Pharmacokinetics/Dynamics Study

27 (1.1)

234 (1.3)

−0.2

0.3 to −0.5

 

Bio-equivalence Study

5 (0.2)

90 (0.5)

−0.3

0 to −0.5

 

Bio-availability Study

1 (0.0)

47 (0.3)

−0.2

−0.2 to −0.3

Type of arms‡, n (%)

    
 

Experimental

1743 (84.3)

13063 (73.4)

10.4

9 to 12

 

Active comparator

458 (22.2)

7569 (42.8)

−20.7

−19 to −23

 

Placebo comparator

343 (16.6)

4701 (26.6)

−10.0

−8 to −12

 

Sham comparator

6 (0.3)

346 (2.0)

−1.7

−1 to −2

 

No Intervention

73 (3.5)

1908 (10.8)

−7.3

−6 to −8

 

Other

84 (4.1)

111 (6.3)

3.4

3 to 4

Blinding, n (%)

    
 

Open

2137 (78.7)

10967 (52.2)

26.6

25 to 28

 

Single

89 (3.3)

2680 (12.8)

−9.5

−9 to −10

 

Double

488 (18.0)

7370 (35.1)

−17.1

−15 to −19

  1. *Denominators exclude missing values. Missing data elements [Rare(%), Non-Rare(%)]: No. of Facilities [35(1.3),89(0.4)]; Primary purpose [72(2.6),898(4.2)]; Study has DMC [482(17.5),3544(16.6)]; Intervention model [77(2.8),577(2.7)]; Allocation [83(3.0),434(2.0)]; Endpoint Classification [354(12.8),3581(16.8)]; Type of arms [692(25.1),3650(17.1)]; Blinding [45(1.6),312(1.5)].
  2. †Data Monitoring Committee.
  3. ‡Studies can belong to multiple categories.
  4. ¥42% of studies labelled as single arm trials were missing allocation information. Whilst some missing data is inferred (see methods section) the trials still missing allocation information are predominantly single-arm trials but missing group data. This allows there to be more single group assignment trials than there are non-randomised trials for the non-rare disease dataset.
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Orphanet Journal of Rare Diseases

ISSN: 1750-1172