Types of clinical trials

Different types of clinical trials available depend on the purpose of the study. Clinical research involving the human subjects known as clinical trials. It does not necessarily mean that you have to give medication/ intervention to the research subjects. Some studies does not given any study medication, even some studies only observe healthy volunteers for particular period of time to achieve their objectives. Depend upon the purpose of study different types of clinical trials conducted.

Here one thing should be noted that types of clinical trials are different from types study designs used in the clinical studies.  Depend upon the purpose, types of clinical trials broadly divided as follows.

1. Interventional trials:

Intervention trials also known as Experimental studies. In this type, one or more treatments or interventions allotted to a group of research subjects to measure the treatment related outcome. Depend upon the allocation of intervention to the study groups, again based study designs, interventional trials divided into following types.

a. Randomised control trials (RCT):

Interventions allotted to the research subjects based on randomization method and pattern used for the study. Intentional allocation of treatment to particular subject is not possible in this study design, it helps to avoid bias. These are the  most commonly performed interventional trials. RCT can be divided into two types

i. Parallel randomized controlledtrials: Treatment groups receive the randomly allotted treatments till the end of the study.

For e.g.: If intervention ‘X’ allotted to group A, and intervention ‘Y’ to group B. Group ‘A’ and ‘B’ will only receive intervention ‘X’ and ‘Y’ respectively till end of the study

ii. Cross-over randomized controlledtrials:   Treatment groups will receive both the interventions in the study period at any phase.

For e.g.: In the same case mentioned above, treatment group A and B will receive both the interventions X and Y. 

b. Non randomised control trials:

In this design, you can allot particular intervention to particular group.

c. Pre-post trials:

Here, usually one group used for study. One group of subjects observed for a particular period of time with no intervention. After some time the intervention allotted. Outcome compared with pre and post intervention to know the effect of intervention.

Note: Types of clinical trials are different from phases of clinical trials that is phase I,II,III, and IV. All phases of clinical trials except phase IV trials are a type of interventional trials. You can also see the overview of phases of clinical trials here.

2. Observational studies:

These studies also known as Non-interventional studies or epidemiological studies. It means interventions are not allotted to research subjects. It mean that the patients may or may not taking their regular medication but these medications are not allotted by the researcher like a interventional study.  Different types of Observational studies based on their study design are as follows.

a. Cross sectional studies:

Cross sectional studies also called as prevalence studies. These studies conducted at one point of time. Study duration also very less compared to other observational studies.  The main objective of these studies to find a possible link between the risk factor or cause and interested outcome. Usually, these studies done retrospectively.

For e.g.: A study finding that how many persons in a group are chronic alcohol abusers and how many persons have liver cirrhosis in that group.

b. Cohort studies:

Cohort is nothing but a group of people with similar status or characteristics. It involves several types of cohorts or groups. These cohorts observed over a period of time.

For e.g. several groups observed for a particular period to know which group developed interested outcome which group not developed the outcome.

 These studies done usually based on the outcome from a cross sectional studies. These studies can be done prospectively as well as retrospectively. Prospective studies are of great value compared to retrospective studies because retrospective studies may have recall bias.

c. Case-control studies:

Researcher recruits the subjects based on their disease status. One group of subjects having a disease act as a test group and another group of subjects not having a disease act as control. In both groups, researcher look back at various factors of those subjects. If a particular factor present in all the diseased subjects, that factor will be compared with control subjects to draw the exposure-outcome relationship conclusions.  These studies are retrospective studies and have recall bias.

For e.g: A case control study to compare the kidney failures in diabetic patients as compared with non diabetics.

Apart from these studies, other types of observational studies are also available like ecological studies and proportional mortality studies etc.

Other clinical trials:

Apart from interventional and observation clinicaltrials, other types are also available. They are prevention trials and screening trials etc.

a. Prevention trials:

These studies conducted using healthy volunteers to find the prevention strategies. These studies conducted for a long period of time.

b. Screening trials:

These studies conducted in a general population or in a subjects with high risk to a particular disease. The objective of these trials is to identify diseased subjects as early as possible before showing disease symptoms.

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List of clinical trial registries in the world

List of clinical trial registries:

Clinical trial registries list provided here with the website urls.

Clinical trial registry is an official website that allows us to registering the clinical trials. Any body can register the clinical trails in the registry who will sponsor the study or by any organisation who is conducting the study. Usually Pharmaceutical or medical or biotech companies or research institutes will register the trials in the clinical trial registries.

Two types of registries available. They are primary registry and partner registry.

Primary registry:

Primary registries are developed according to the specific criteria given by World Health Organisation (WHO) International Clinical trial registry platform (ICTRP) This specific criteria include these 6 categories. That is Content, quality &validity, Accessibility, Unambiguous Identification, Technical capacity, Administration &governance.  Primary registry meets the requirements of International committee of medical journal editors (ICMJE). Registration of trial in the clinical trial primary registry in the WHO network or USA Clinical trial registry (Clinicaltrials.gov) is mandatory for publishing the study in international biomedical journals. ICMJE announced this statement 15 years back and applicable from July 1st 2005 onwards. All these primary registries are linked to the WHO- ICTRP. ICTRP can directly receive the data from these primary registries.

clinical trial registries

Related: Clinical trials overview

A total number of 16 registries recognized as primary registries in the WHO registry network. Along with these 16 registries Clinical trials.gov (USA) recognized by ICMJE. Along with USA registry Clinicaltrials.gov, these 16 primary registries act as data providers to WHO. This data available in the WHO ICTRP search portal. WHO ICTRP search portal is technically not considered as a clinical trial registry. 

For eg: If you register a clinical trial in any of these 17 clinical trial registries, you can find that trial in WHO ICTRP search portal. Registries registered trail data upload to ICTRP search portal periodically.

Australia, China, UN, EU, Netherlands, USA registries uploaded Friday of the every week. Remaining registries data uploaded monthly basis.Types of clinical trial registries

List of clinical trial registries recognized by WHO network and ICMJE are follows.

List of clinical trial registries (Primary)

1. Australian New Zealand CTR (ANZ Clinical Trial Registry) –  http://www.anzctr.org.au

2. Brazilian CTR (ReBec) – http://www.ensaiosclinicos.gov.br/

3. Chinese CTR (ChiCTR) – http://www.chictr.org.cn/ 

4. Republic of korea Clinical Research Information Service (CRiS), – https://www.who.int/ictrp/network/cris2/en/

5. CTR – India (CTRI) – http://ctri.nic.in

6. Cuban Public Registry of Clinical Trials (RPCEC) – http://registroclinico.sld.cu/

7. European Union CTR (EU-CTR) – https://www.clinicaltrialsregister.eu/

8. German CTR (DRKS)  – https://www.drks.de

9. Iranian Registry of Clinical Trials (IRCT) – https://www.irct.ir/

10. United Kingdom for International Standard Registered Clinical/soCial sTudy Number (ISRCTN) – http://www.isrctn.com/

11. Japan Primary Registries Network (JPRN) – http://rctportal.niph.go.jp/  (It has four networks JapicCTIJMACCT CTRjRCTUMIN CTR )

12. Thai CTR (TCTR) – http://www.clinicaltrials.in.th/

13. The Netherlands National Trial Register (NTR) – https://www.trialregister.nl/

14. Pan African CTR (PACTR) – https://pactr.samrc.ac.za/

15. Peruvian CTR (REPEC) – https://ensayosclinicos-repec.ins.gob.pe

16. Sri Lanka CTR (SLCTR) – http://www.slctr.lk/

 USA – https://clinicaltrials.gov/ (Recognised by ICMJE, It is not in the list of WHO registry network but act as data provider to WHO ICTRP)

WHO ICTRP- http://apps.who.int/trialsearch/ (Technically not called as a clinical trial register)

Related: Job opportunities after pharmacology graduation

Partner registry:  

Partner registries does not meet the requirements of ICMJE. But partner registry meets the WHO ICTRP specific criteria as mentioned above. They are affiliated to ICMJE registered primary registry or Primary registry in WHO network. It is the responsibility of primary registry to make sure that the partner registry meets the WHO registry criteria. ICTRP directly will not have access to receive the data from these partner registries. Along with 16 primary registries two partner registers available. These two registries are affiliated to Chinese clinical trial registry (ChiCTR). Partner registries can also be called as secondary registries. They are as follows.

  1. Centre for Clinical Trials, CTR – Chinese University of Hong Kong – http://www2.ccrb.cuhk.edu.hk/web/
  2. The Acupuncture-Moxibustion Clinical Trial Registry (AMCTR) Beijing
  3. Apart from these registries, other available registries are as follows.
List of clinical trail registries (Regional)
  1. Canadian cancer trials – http://www.canadiancancertrials.ca/ ( Canadian based cancer registry –Only for cancer clinical trails in Canada)
  2. Health Canada Clinical Trial Database – http://www.hc-sc.gc.ca/dhp-mps/prodpharma/databasdonclin/index-eng.php (It is technically not called as a registry)
  3. Hong Kong University clinical trials registry (HKUCTR)- http://www.hkuctr.com/
  4. Indonesia clinical trial registry- https://ina-registry.org/
  5. NBScience Clinical trial registry  (NBSCTR)- Ukraine – http://www.nbscience.com/
  6. Philippine Health Research Registry (PHRR) – http://registry.healthresearch.ph
  7. Swiss National Clinical Trials Portal (SNCTP) – http://www.kofam.ch/en/swiss -clinical-trials-portal.html
  8. South African National Clinical Trial Register (SANCTR) – http://www.sanctr.gov.za/
  9. Spanish registry of Clinical trials (REec) – https://reec.aemps.es
  10. Tanzania Clinical Trial Registry (TzCTR) – http://www.tzctr.or.tz/  

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