A prospective observational study is usually called a
cohort study.
A group of patients is identified to receive a specific
treatment and then treated, and their results are followed
serially over time.
The essential feature of a cohort study is its prospective
nature.
A study design is considered,and a priori power analysis is
performed to determine the necessary sample size
The study is announced publicly (in a sense) by institutional
review boards for human subjects
Then, the treatment is administered.
The outcomes of interest are followed at well-defined intervals.
All data are gathered up to a minimum interval (e.g., 2 years of
follow-up) for analysis.
In practice, all cohort studies involve a control group, which
consists of patients who have the same diagnosis but different
treatment, such as a gold-standard treatment or conservative
management.
Ideally, the control group is defined prospectively as well and
follows an identical clinical protocol, except for the treatment.
In some cohort studies, matching is used to identify
control patients.
In matching, patients who have similar demographic or clinical
variables, such as gender, age, and co-morbidity, are compared.
Matching is a way of controlling for confounding
variables in observational studies.
Prospective studies have the advantage of being a well-defined and
principled type of observational study
Since there is no randomization, all the potential biases and
confounders exist in this type of study.