community interventional trials

1. Community trials
Dr. M. Krishnaveni
Associate Professor
Narayana pharmacy college, Nellore

2. Introduction to community trials
• Community trials are an extension of field trials. In community trials the study
group is the entire community, rather than individuals.
• Conceptually, the difference is whether or not the intervention is implemented
separately for each individual.
• If only two communities are involved in a study, one of which will receive the
intervention and the other will not, random assignment of the community that
receives the intervention is not required; differences in baseline characteristics will
be the same whatever the method of assignment-only the direction of the
differences will be affected.
• Example: to study the efficacy of adding fluoride to the community water supply to
prevent dental decay, two similar towns in New York State were studied in the
Newburgh-Kingston water fluoridation trial (Ast et al, 1956. In one town, fluoride
was added to the water supply; nothing was done to the other town. Residents of
both towns had dental examinations over a period of several years to measure the
effect of the intervention. The outcome was that fluoride helped to prevent
parodontids.

3. The community approach - essentiality
• Most common health problems amenable to prevention have strong
environmental, cultural, lifestyle, and behavioral components.
• People, communities, whole countries make choices about whether or not
to consume alcohol, and drive, smoke cigarettes, exercise, or have their
children immunized.
• All of these involve individual choices but also involve societal or cultural
barriers and enticements, access, and availability, monetary and
opportunity costs, laws, and other community-wide factors.
• While some prevention issues respond to traditional clinical or health
care approaches, most do not.
• They require a coordinated community approach to support the
preventive efforts of the health care sector and develop an environment and
an educated population which makes prevention possible.
• If we are to approach true primary prevention or elimination of major
health impairing conditions, the population approach is a necessary
element.

4. Community trials- criteria
• Common condition
• Established risk factors
• Sociocultural determinants
• Reasonable interventions available
• Benefits of intervention demonstrated
• Safety
• Acceptable to community

5. Community trials: experience
• Community involvement
• Mass media
• Screening and education
• Youth education
• Professional education
• Environmental changes
• Analytical methods

6. Advantages of community trial
• Provides information in making public health
decisions and optimises national lhealth
programs
• Easy to change community social
environment
• Community norms changes high risk life styles
and behaviours
• In natural or normal community environment
interventions are tested.

7. Disadvantages
• High chance of selection bias
• Controls getting the interventions

8. • In community intervention studies , the
exposure is given to subjects.
• Eg- by vector control to reduce malaria
– Pit latrines for clean water

9. Characterstics of community
intervention studies
1. Explicitly nutritional
Nutrition oriented food programs
Feeding programs
Weaning foods
Fortification
Nutrition education
2.Non or implicitly nutritional
Health related
Economic
3.integrated

10. Study design
• intervention studies are generally time consuming and costly. They
cost more than observation studies as they normally require
dedicated staff to coordinate them (personnel to evaluate and recruit
patients, carry out follow up, etc.)
• It is even more important to clearly define the research question to
be answered and estimate how great an effect must be observed for
the intervention to be deemed successful.
• It is not always possible, desirable or ethical to carry out an
intervention study and not all health care intervention can be
assessed in this way. There must be sufficient doubt about the
benefits and risks of a new intervention compared with the usual or
no treatment for it to be considered ethical to allocate participants to
one or other group.
• Another major consideration for an intervention study is the sample
size required.

11. Selection of study population
• Those who are eventually found to be both eligible and
willing to enroll in the trial compose the actual study
population and are often a relatively small and selected
subgroup of the experimental population.
• Participants in an intervention study are very likely to differ
from non- participants in many ways that may affect the risk
of development of the outcomes under investigation.
• Whether or not the subgroup of participants is
representative of the entire experimental population will not
affect the validity of the results of a trial conducted among
that group. It may, however, affect the ability to generalize
those results to either the experimental or the target
population

12. Allocation of treatment regimens
• In any intervention study, the investigator will
allocate the participants either to the intervention
group, which will receive the therapy or
preventive action under study, or to the control
group, which will receive the usual or no
treatment.
• The two groups are then compared on outcome of
interest. To avoid any underlying differences
between the two groups affecting the outcome, it
is important that the groups are similar in all other
respects.

13. Random allocation
• Random allocation is the best method of
allocating the study subjects to the different study
groups. This method allows chance, and only
chance, to determine the assignment of subjects to
the various groups
• It is, therefore, the only way of ensuring that any
differences in the outcome measures of the trial
are due to the effects of the intervention rather
than to underlying differences between the
groups.

14. • Randomisation eliminates selection bias on the
part of the participants and investigators •
Randomization tends to create groups that are
comparable in terms of the distribution of
known and, more importantly, unknown
factors that may influence the outcome.
Randomization has two major advantages in
relation to other methods of allocation.

15. Simple randomization
• Simple randomization is the most elementary
method of randomization.
• It is the equivalent of tossing a coin. However,
randomization by tossing a coin should not be
used because it cannot be checked or reproduced.
• One of the disadvantages of simple
randomization is that it may result in markedly
unequal number of subjects being allocated to
each group just by chance

16. Blocked randomization
• This method guarantees that the numbers of participants
allocated to each study group are equal after every block of
so many patients has entered the trial. Suppose that patients
are going to be allocated to treatments A and B in such a
way that after every fourth subject there are an equal
number of participants on each treatment.
• The combination for a particular block of four patients is
chosen at random from the six possible it would mean that
patients would receive treatments ABAB, ABBA, BAAB
and BABA, respectively.
• This procedure thus allocates eight patients to group A and
eight to group B

17. Efficacy and effectiveness
• All trials test the efficacy of an intervention
and assess the effectiveness.
• The Field Trial it evaluate efficacy of
intervention designed to prevent disease, e.g.,
vaccine, vitamin supplement, patient education

18. Stratified randomization
• When the results of the trial are likely to vary between, say,
the sexes or different age-groups, stratified randomization
should be used. In this situation, strata or groups are formed
and randomization occurs separately for the subjects in each
stratum.
• As subjects become eligible for inclusion in the trial, their
appropriate stratum is determined and they receive the next
random-number assignment within that stratum.
• Stratified randomization has the advantage of assuring
balance between the groups, at least on the characteristics
that determine the strata.
• The disadvantage with stratified randomization is that it is
administratively difficult and cumbersome to execute

19. Measurement of outcomes
• Measurement (or reporting bias) can be minimized by
blinding trial investigators and participants to the allocated
treatment. If both the investigator and participant are
blinded, the study referred to as double-blind. If it is either
the participant or investigator that is blinded, the study is
single-blind.
• Sometimes it is not possible to keep the allocation of the
intervention hidden from the participant or the investigator.
For example, if the study is to compere the effect of
mosquito nets versus antimalarial tablets, then the
participant will know which intervention they are receiving,
although it might still be possible to keep allocation of
groups from microscopists who analyse the blood samples.

20. Analysis
• The main method of analysis of an intervention study should be by
intention to treat. This means that the analysis should include results from
all study participants by the groups to which they were allocated at the start
of the study, even if they swapped groups or subsequently dropped out of
the study.
• This method avoids potential biases that can arise from different levels of
participation, and also because non-participants are usually different from
those who complete a study in terms of their risk of side effects.
• It also ensures that the study is relevant to the real world since if only
individuals who complete their treatment are included in the analysis, the
study will not necessarily be an accurate representation of what will happen
when the intervention is used in general population, in whom compliance is
rarely, if ever, 100%. It is of course possible to analyze a study for only
those who receive and complete their treatment regimen, but this should
always be clearly stated when the results of the study are reported.

21. Interpretation
• Once the results have been analysed, the investigator need
to decide whether the results are wholly due to the
intervention or whether they could be explained by other
factors.
• If the trial has been carried out correctly, and the
randomization and blinding procedures are effective, then
there should be few problems with bias and confounding.
• It is important to distinguish between results that are
statistically significant and those that are clinically
significant. It may be that a result has reached statistical
significance but because of other factors such as drug side
effects, other adverse events and costs of implementation
the treatment of interest may not be seen as a visible
alternative to the next best treatment.

22. Ethical issues
• In intervention trials ethical considerations are more
important than in any other type of epidemiological
study.
• Intervention trials are ethically justified only in a
situation of uncertainty, when there is genuine doubt
concerning the value of a new intervention in terms of
its benefits and risks.
• The researcher must have some evidence that it may be
of benefit, for instance, from laboratory and animal
studies, or from observational epidemiological studies.
• Otherwise, there would be no justification for
conducting a trial.

23. • Before the participants are recruited into atrial, it is
important that they are fully aware of what the study is
about, what it is for and what the potential risks are.
Participants then need to give their consent to participate.
This is known as informed consent.
• Sometimes it is not possible for the participant to provide
their consent. For example , if the intervention is a
childhood vaccine, then the consent will need to be sought
from the parent or guardian of the child; and if intervention
is a drug that is hoped to improve the recovery of patients
with severe head injuries , then it is likely that consent will
be required from close relative or guardian. Whatever form
of consent is obtained, it should always be clearly stated
when the results of the trial are reported.

24. Recommendations for next generation
of community trials
• New community trials
• Trials within communities’studies of youth
• Underserved groups
• Environmental change

25. References
• Am J Public Health Nations Health. 1956 Mar;
46(3): 265–271. doi: 10.2105/ajph.46.3.265
•