Research in Medicine: Basic Types and Methods

Medical Research and Study Design
The scientific value and informativeness of a medical study are determined to a major extent by the study design.
Errors in study design cannot be corrected afterwards.

5 phases of medical research
Planning
Performance
Documentation
Analysis
Publication

The importance of study design
Planning study design:
a suitable type of study
an overall plan for all procedures
a bias to be minimized

6 aspects of study design
the question to be answered,
the study population,
the type of study,
the unit of analysis,
the measuring technique
the calculation of sample size

The question to be answered
research objectives = the key research question
must be
operationalized converted into a measurable and evaluable form.
main questions vs secondary questions.
as a result open questions are answered and new hypotheses are possibly generated.

Descriptive analysis
the units of analysis are to be described by
the recorded variables (e.g. blood parameters or diagnosis)

Exploratory analysis
to recognize connections between variables,
to evaluate connections,
to formulate new hypotheses.

Confirmatory analysis
to provide statistical proofs by testing specified
study hypotheses

Unit of analysis
clinical study
systematic reviews
patient
hereditary information,
a cell,
a cellular structure,
an organ, an organ system,
a single test individual (animal or man),
a specified subgroup or
the population of a region or of a country.
a single study
The interesting information or data (observations, variables, characteristics) are recorded for the statistical units.

Measuring technique
measuring instruments:
to record measuring data (such as blood pressure or laboratory parameters)
to collect data with standardized or self-designed questionnaires (for example, quality of life, depression, or satisfaction).

Classification of study types
Primary Research
Secondary Research
actual studies
summarizes available studies in the form of reviews and meta-analyses

Primary Research: Main Categories
basic medical research ( or experimental research)
clinical research epidemiological research

BASIC MEDICAL RESEARCH
also known as experimental research
Aim: to acquire new knowledge without looking for long-term benefits other than the advancement of knowledge
includes: animal experiments, cell studies, biochemical, genetic and physiological investigations, and studies on the properties of drugs and materials

CLINICAL RESEARCH
interventional (or experimental)
studies on drugs, medical
devices and
studies in which surgical,
physical or
psychotherapeutic
procedures are examined.
noninterventional (or observational) -
a study in which knowledge from the treatment of persons is analyzed using epidemiological methods. The diagnosis, treatment and monitoring are performed exclusively according to medical practice.

Clinical Studies (Clinical Trials)
Aim: to determine better ways to prevent, screen for, diagnose or treat diseases.
Controlled trial (a study group and a control group)
Randomization ( a randomized controlled trial)
Blinding ( single and double blind trial)

EPIDEMIOLOGICAL RESEARCH
the description of health and welfare in
populations through the collection of data related
to health and the frequency, distribution and
determinants of disease in populations, with the
aim of improving health.

Epidemiological:
interventional or experimental
field studies
group studies
sample from an area, such as a large region or a country
e.g. investigation of the iodine supplementation of cooking salt to prevent cretinism in a region with iodine deficiency
sample from a specific group, such as a specific social or ethnic group.

Epidemiological:
observational
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. Possible exposure factors include smoking, nutrition and pollutant load.

Epidemiological:
observational
Cohort studies ( prospective and retrospective)
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.

Common study types for epidemiological investigations
Study objective
Study of severe diseases such as cancers
Study of rare exposure, such as exposure to industrial chemicals
Study of multiple exposures, such as the combined effect of oral contraceptives and smoking on myocardial infarction
Study type
Case control studies
Cohort studies in a population group (e.g. industrial workers
Case control studies
(Dtsch Arztebl Int. 2009 April; 106(15): 262–268. )

References
http:// www.experiment-resources
http://www.nhs.uk/Conditions/Clinical-trials
Glossary of Clinical Trials Terms
Altman DG. Randomisation: potential for reducing bias. BMJ. 1991;302:1481–1482. [PMC free article] [PubMed]
Study Design in Medical Research //Dtsch Arztebl Int. Mar 2009; 106(11): 184–189. Published online Mar 13, 2009. doi: 10.3238/arztebl.2009.0184
Types of Study in Medical Research// Dtsch Arztebl Int. Apr 2009; 106(15): 262–268.Published online Apr 10, 2009. doi: 10.3238/arztebl.2009.0262
Study designs in medical research http://galton.uchicago.edu/