community trials.pptx

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. D isadvantages 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 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 R andom  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. Measuremen t 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