An Introduction Researching Programs: Practical Considerations Researching Programs: Drafting Your Statement Statements of Purpose: The Basics In-Text Citations: Basic Rules Reference List: Articles in Periodicals Reference List: Other Print Sources Reference List: Electronic Sources Reference List: Organization and Structure Graduate Writing Workshops: Introductions Graduate Writing Workshops: Literature Reviews Graduate Writing Workshops: Style Graduate Writing Workshops: Editing and Proofreading Graduate Writing Workshops: Copyright and Plagiarism Collaborative Authorship Handout: Specificity in Writing Grant Writing: Basic medical research otherwise known as experimental research includes animal experiments, cell studies, biochemical, genetic and physiological investigations, and studies on the properties of drugs and materials.
In almost all experiments, at least one independent variable is varied and the effects on the dependent variable are investigated. The procedure and the experimental design can be precisely specified and implemented 1. For example, the population, number of groups, case numbers, treatments and dosages can be exactly specified. It is also important that confounding factors should be specifically controlled or reduced.
In experiments, specific hypotheses are investigated and causal statements are made. External validity is a more difficult issue. Basic research also includes the development and improvement of analytical procedures—such as analytical determination of enzymes, markers or genes—, imaging procedures—such as computed tomography or magnetic resonance imaging—, and gene sequencing—such as the link between eye color and specific gene sequences.
The development of biometric procedures—such as statistical test procedures, modeling and statistical evaluation strategies—also belongs here. Clinical studies include both interventional or experimental studies and noninterventional or observational studies.
Interventional studies also include studies on medical devices and studies in which surgical, physical or psychotherapeutic procedures are examined. The diagnosis, treatment and monitoring are not performed according to a previously specified study protocol, but exclusively according to medical practice.
The aim of an interventional clinical study is to compare treatment procedures within a patient population, which should exhibit as few as possible internal differences, apart from the treatment 4 , e1. This is to be achieved by appropriate measures, particularly by random allocation of the patients to the groups, thus avoiding bias in the result. Possible therapies include a drug, an operation, the therapeutic use of a medical device such as a stent, or physiotherapy, acupuncture, psychosocial intervention, rehabilitation measures, training or diet.
Vaccine studies also count as interventional studies in Germany and are performed as clinical studies according to the AMG. Interventional clinical studies are subject to a variety of legal and ethical requirements, including the Medicines Act and the Law on Medical Devices. Studies with medical devices must be registered by the responsible authorities, who must also approve studies with drugs. Drug studies also require a favorable ruling from the responsible ethics committee.
For clinical studies on persons capable of giving consent, it is absolutely essential that the patient should sign a declaration of consent informed consent e2. A control group is included in most clinical studies. The selection of the control group must not only be ethically defensible, but also be suitable for answering the most important questions in the study e5.
Clinical studies should ideally include randomization, in which the patients are allocated by chance to the therapy arms. This procedure is performed with random numbers or computer algorithms 6 — 8. Randomization ensures that the patients will be allocated to the different groups in a balanced manner and that possible confounding factors—such as risk factors, comorbidities and genetic variabilities—will be distributed by chance between the groups structural equivalence 9 , Randomization is intended to maximize homogeneity between the groups and prevent, for example, a specific therapy being reserved for patients with a particularly favorable prognosis such as young patients in good physical condition Blinding is another suitable method to avoid bias.
A distinction is made between single and double blinding. With single blinding, the patient is unaware which treatment he is receiving, while, with double blinding, neither the patient nor the investigator knows which treatment is planned.
Blinding the patient and investigator excludes possible subjective even subconscious influences on the evaluation of a specific therapy e. Thus, double blinding ensures that the patient or therapy groups are both handled and observed in the same manner. The highest possible degree of blinding should always be selected.
The study statistician should also remain blinded until the details of the evaluation have finally been specified. A well designed clinical study must also include case number planning. This ensures that the assumed therapeutic effect can be recognized as such, with a previously specified statistical probability statistical power 4 , 6 , It is important for the performance of a clinical trial that it should be carefully planned and that the exact clinical details and methods should be specified in the study protocol It is, however, also important that the implementation of the study according to the protocol, as well as data collection, must be monitored.
For a first class study, data quality must be ensured by double data entry, programming plausibility tests, and evaluation by a biometrician. Many journals make this an essential condition for publication.
For all the methodological reasons mentioned above and for ethical reasons, the randomized controlled and blinded clinical trial with case number planning is accepted as the gold standard for testing the efficacy and safety of therapies or drugs 4 , e1 , In contrast, noninterventional clinical studies NIS are patient-related observational studies, in which patients are given an individually specified therapy.
NIS include noninterventional therapeutic studies, prognostic studies, observational drug studies, secondary data analyses, case series and single case analyses 13 , The evaluation is often retrospective.
Prognostic studies examine the influence of prognostic factors such as tumor stage, functional state, or body mass index on the further course of a disease. Diagnostic studies are another class of observational studies, in which either the quality of a diagnostic method is compared to an established method ideally a gold standard , or an investigator is compared with one or several other investigators inter-rater comparison or with himself at different time points intra-rater comparison e1.
If an event is very rare such as a rare disease or an individual course of treatment , a single-case study, or a case series, are possibilities. A case series is a study on a larger patient group with a specific disease.
The lack of a control group is a disadvantage of case series. For this reason, case series are primarily used for descriptive purposes 3. The main point of interest in epidemiological studies is to investigate the distribution and historical changes in the frequency of diseases and the causes for these.
Analogously to clinical studies, a distinction is made between experimental and observational epidemiological studies 16 , Interventional studies are experimental in character and are further subdivided into field studies sample from an area, such as a large region or a country and group studies sample from a specific group, such as a specific social or ethnic group. One example was the investigation of the iodine supplementation of cooking salt to prevent cretinism in a region with iodine deficiency.
On the other hand, many interventions are unsuitable for randomized intervention studies, for ethical, social or political reasons, as the exposure may be harmful to the subjects Observational epidemiological studies can be further subdivided into cohort studies follow-up studies , case control studies, cross-sectional studies prevalence studies , and ecological studies correlation studies or studies with aggregated data.
In contrast, studies with only descriptive evaluation are restricted to a simple depiction of the frequency incidence and prevalence and distribution of a disease within a population.
The objective of the description may also be the regular recording of information monitoring, surveillance.
Registry data are also suited for the description of prevalence and incidence; for example, they are used for national health reports in Germany. In the simplest case, cohort studies involve the observation of two healthy groups of subjects over time.
One group is exposed to a specific substance for example, workers in a chemical factory and the other is not exposed. It is recorded prospectively into the future how often a specific disease such as lung cancer occurs in the two groups figure 2a.
The incidence for the occurrence of the disease can be determined for both groups. Moreover, the relative risk quotient of the incidence rates is a very important statistical parameter which can be calculated in cohort studies. For rare types of exposure, the general population can be used as controls e6. All evaluations naturally consider the age and gender distributions in the corresponding cohorts.
The objective of cohort studies is to record detailed information on the exposure and on confounding factors, such as the duration of employment, the maximum and the cumulated exposure. One well known cohort study is the British Doctors Study, which prospectively examined the effect of smoking on mortality among British doctors over a period of decades e7. Cohort studies are well suited for detecting causal connections between exposure and the development of disease.
On the other hand, cohort studies often demand a great deal of time, organization, and money. So-called historical cohort studies represent a special case.
In this case, all data on exposure and effect illness are already available at the start of the study and are analyzed retrospectively.
For example, studies of this sort are used to investigate occupational forms of cancer. They are usually cheaper Graphical depiction of a prospective cohort study simplest case [2a] and a retrospective case control study 2b. In case control studies, cases are compared with controls. Cases are persons who fall ill from the disease in question.
Controls are persons who are not ill, but are otherwise comparable to the cases. A retrospective analysis is performed to establish to what extent persons in the case and control groups were exposed figure 2b.
Possible exposure factors include smoking, nutrition and pollutant load. Care should be taken that the intensity and duration of the exposure is analyzed as carefully and in as detailed a manner as possible. If it is observed that ill people are more often exposed than healthy people, it may be concluded that there is a link between the illness and the risk factor.
In case control studies, the most important statistical parameter is the odds ratio. Case control studies usually require less time and fewer resources than cohort studies The disadvantage of case control studies is that the incidence rate rate of new cases cannot be calculated.
There is also a great risk of bias from the selection of the study population "selection bias" and from faulty recall "recall bias" see too the article "Avoiding Bias in Observational Studies". Table 1 presents an overview of possible types of epidemiological study e8. Table 2 summarizes the advantages and disadvantages of observational studies However, the scientific questions can only be correctly answered if the study is planned and performed at a qualitatively high level e9.
It is very important to consider or even eliminate possible interfering factors or confounders , as otherwise the result cannot be adequately interpreted. Confounders are characteristics which influence the target parameters.
Although this influence is not of primary interest, it can interfere with the connection between the target parameter and the factors that are of interest. The influence of confounders can be minimized or eliminated by standardizing the procedure, stratification 18 , or adjustment The decision as to which study type is suitable to answer a specific primary research question must be based not only on scientific considerations, but also on issues related to resources personnel and finances , hospital capacity, and practicability.
Primary research usually costs more and often takes longer to conduct than secondary research, but it gives conclusive results. Secondary research is a type of research that has already been compiled, gathered, organized and published by others.
The four types of primary market research By Samantha Garner | October 21, Primary market research is a great way to gather information about your small business’ product or service idea.
Primary research is a time-tested method, therefore, one can rely on the results that are obtained from conducting this type of research. Disadvantages of Primary Research One of the major disadvantages of primary research is, it . Secondary research is defined as an analysis and interpretation of primary research. The method of writing secondary research is to collect primary research that is relevant to a writing topic and interpret what the primary research found.
There are different types of primary data and they are used according to the type of study. Some of the most prominently used methods of primary data collection include observation, interview, questionnaire and experiments. Primary Market Research Methods. There are two forms of research: primary research and secondary research. Primary research is proprietary research, which means the data is collected directly from the research subject/area, by the researcher.