Narrative review studies on Pharmaceutical Assistance: What is their validity?

Estudos de revisão narrativa na área de Assistência Farmacêutica: qual a validade?

Abstract

Among health technologies, medicines represent a large share of public expenditure with health. As
new medicines come to the market every year, pharmaceutical laboratories, users and health professionals
generate demands that they be incorporated by the public health system. Such demands have grown
substantially, placing important pressure on decision makers.
The information about medicine cost-efficacy-safety and drug use may come either from primary studies
(controlled and randomized clinical trials with representative samples or methodologically well-elaborated
cohorts with consistent results and large estimated effect) or from secondary studies (systematic reviews and
meta-analyses), or even from tertiary studies (synopsis or evidence synthesis, among others).
Studies which comprise issues regarding treatment are ranked according to the level of confidence
about results, that is, according to their internal and external validity. The ranking is based on methodological
restraints regarding the type of study, given that independently of researchers’ efforts, the complete
elimination of some types of biases (systematic errors) is unattainable. For instance, we can quote cohort
studies in which the selection bias cannot be eradicated due to patients not randomized before becoming
study subjects, and also retrospective studies (control cases), which hardly ever eliminate the memory
bias, registry failure, data confirmation, etc.
Thus, observational studies present bigger methodological restraints to establish the connection
between studied outcome and intervention, resulting in lower levels of evidence than randomized clinical
trials. The same reasoning is applicable to secondary studies. Systematic reviews are placed at the top of
the evidence pyramid, whereas the narrative reviews (experts’ judgments) are at the base of the pyramid,
following to pre-clinical studies.
In the context of health research, the word evidence should be understood as the body of facts (proof)
or the information available indicating that the findings to answer a problem are true or valid.
We should consider the evidence level where the study is placed in the selection process for decision
making in Health. Information provided by more highly ranked studies are to have superior scientific
value to answer a question with better levels of results validity (provided they are methodologically well
designed) than those placed at lower levels. Anyway, in the Health decision making process, and especially
in Pharmaceutical Services issues, we must weigh all the available evidence and its level of confidence
rather than simply choose those supporting our ideas or interest conflicts.
Strictly speaking, I would like to discuss the role of Pharmaceutical Services reviews. The reviews
show to be the most demanded type of paper in scientific libraries and journals. Review studies feature
the information analysis and synthesis available in all the relevant studies published on a specific theme/
issue, so as to summarize the body of knowledge available and wrap up the theme. There are several types
of review studies, and each of them follows a specific methodology.
In this editorial, we will highlight narrative reviews or literature reviews, as they are usually called.
Narrative reviews have a qualitative approach, that is, they neither have a methodology which allows
data reproduction nor provide quantitative answers for specific issues. They usually comprise the state of
the art (up-to-date knowledge) stemming from the descriptive trajectory and the distribution of scientific
production on the theoretical and contextual perspective. This type of study establishes relationships
with previous productions, identifies recurrent themes, points out new perspectives, or those which have
received slighter emphasis in the literature.
There may be very good reasons for writing a quality narrative review. For example, narrative syntheses
are useful educational papers once they group information in a format to make comprehension easier.
They are also helpful in presenting a broad perspective on a theme, and they often describe the history or
the development of the problematic issue, and its management.