Method and representation
Most of the included studies described a 2 or 3 round Delphi survey,
followed by a face-to-face consensus meeting to finalize the COS.
However, some completed studies included only Delphi surveys and one
study by Fiala et only undertook a consensus-meeting. The consensus
criteria most commonly used for an outcome to be included in the COS was
the 70/15 (more than 70% rates the outcome as critically important and
less than 15% rates it as not important).
The number of outcomes included in
the COS ranged between 6 and 48 (Figure3C, Table 1). Only a few studies
had less than 10 outcomes in the final COS. None of the ongoing studies
mentioned that they had determined or discussed in advance a possible
limit to the number of outcomes to be included in the COS to enable
implementation and feasibility in research. Two studies described using
a “modified nominal group technique” during the consensus meeting in
order to reduce outcomes (17, 18).
Researchers were included in all identified studies and healthcare
personnel in the majority. Patients were sometimes not included at all
in the process (10, 23, 25) or only partly included. Some examples are
(8), who used a separate survey consisting of only one round for
patients, (21), where patients were included in the Delphi survey, but
not in the consensus meeting and (20) where two persons served as
proxies for patients . Most of the completed studies involved
international participation.
Nine of the studies were assessed
as complying to the COS-STAR criteria well in most categories (8, 9,
12-15, 17-19), three showed some deviations (11, 21, 24) and six of the
studies were assessed as having major shortcomings in reporting (2, 10,
20, 22, 23, 25-27) table S1. Most of the completed studies lacked
information about whether outcomes had been excluded at some stage or if
outcomes had been merged. No studies mentioned whether they deviated
from the study protocol in any way.
Discussion
Main Findings
Core outcome sets are an agreed standardised collection of outcomes that
should be measured and reported for a specific area of health. These
sets represent the minimum that should be measured and reported in all
clinical trials of a specific condition and are also suitable for use in
other types of research and clinical audits. Although there are examples
of well-established sets such as Outcome Measures in Rheumatology
(OMERACT) for rheumatoid arthritis, they are still relatively rare in
most medical fields. The outcomes in the set should represent the
minimum to be collected in all trials, but researchers should continue
to measure and report additional outcomes of particular relevance to
their topic.
This review of pregnancy and childbirth revealed a complete lack of any
ongoing or existing COS in the field of mental health, such as
postpartum depression, post-traumatic stress disorder after birth, or
postpartum psychosis. Consequently, SBU initiated the development of COS
for studies of treatment of perinatal depression (2, 27). There are only
a few COS on intrapartum care, for such conditions as slow progress in
labour, trial of labour after previous caesarean section and postpartum
endometritis. One of the topics for which most COS have been compiled is
the field of physical conditions and complications during pregnancy.
It is important to consider how many outcomes a COS can include and
still be applicable and useful for research. This systematic review
discloses that the COS identified range between 6 and 48 outcomes. Only
a few of the included finalised COS had less than ten outcomes. None of
the identified studies discussed the relationship between the number of
outcomes in the COS and the median number of outcomes in the studies for
which the COS is intended. Nor did any of the protocols suggest a
possible limit to the number of outcomes that might be included in the
intended COS. In order to increase the implementation of developed COS,
it is important to consider how the number of outcomes included will
affect the usefulness of the COS. Some limitation of outcomes might
increase the likelihood that the COS will be applied in future research.
It is also important to note that the development of a COS which focuses
on what to measure may need to be followed by decisions
about how and when to measure these outcomes. Even if the
outcomes themselves are consistent across the studies, lack of
consistency in how or when outcomes have been measured can undermine
efforts by systematic reviewers to compare, contrast and combine the
results of multiple studies. Unfortunately, very few of the identified
COS mentioned how and when to measure the outcomes in the developed COS.
Strengths and Limitations
Some limitations to the systematic review should be noted. In the
systematic review we checked compliance to COS-STAR in the included
studies. However, it would have been optimal to be able asses the
methodological quality of the included studies using a tool developed
for this purpose. We believe that
the development of such a tool is desirable and that some of the
questions used in this article (Appendix S2) could be helpful. In this
systematic review we decided to have an inclusive approach and might
have included studies that are not principally intended for research
use, but for other purposes, such as clinical follow-up.
This review focuses on maternal health. COS restricted to the infant,
which might also be of interest to researchers, were beyond the scope of
this review.
A strength of this study is that it is methodologically sound and
robust, and all results have continuously been reviewed by experts from
the Swedish Agency for Health Technology Assessment and Assessment of
Social Services (SBU), as well as by external reviewers. Another
strength is the attempt to assess the reporting of the included COS
using an assessment tool based on the COS-STAR reporting guide (Appendix
S2).
Interpretation
In 2017, Duffy et al published a systematic review of published and
ongoing COS related to the health of women and newborns (28). The scope
of their paper is somewhat broader, including conditions other than
those related to pregnancy and childbirth. In all, they identified four
completed COS, of which three were related to obstetric care. In the
last two years, a substantial number of COS have been completed and 39
ongoing studies have been identified.
Conclusion
This systematic review discloses an increasing number of COS for
pregnancy and childbirth. This is gratifying, hopefully leading to
studies which focus on important outcomes and research that is more
readily synthesised in systematic reviews, thus increasing evidence in
support of interventions. The review reveals that a large number of the
ongoing and completed COS studies address physical conditions and
complications during pregnancy. There was a lack of COS for delivery. No
COS was identified for perinatal mental health. Accordingly, SBU
initiated the development of COS for studies of treatment of perinatal
depression (2, 27).
Contribution of authorship: Study concept and design: CH, MÖ,
AS, MJ, FT. Literature search AJ. Selection of studies and extraction of
the relevant information CH and MÖ. Analysis and interpretation of data:
CH, MÖ, AS, MJ, FT. Drafting of the manuscript: CH and MÖ. Critical
revision of the manuscript for important intellectual content: AS, MJ,
FT, CH, MÖ, SF, AJ.
Data availability Data are available on request.
Disclosure of interests: The authors report no conflict of
interest, all authors filed a conflicts of interest form used by Swedish
governmental agencies before engagement. These are available upon
request.
Details of ethics approval: Systematic review, no ethical
approval needed.
Funding: The project was conducted within the Swedish Agency
for Health Technology Assessment and Assessment of Social Services
assignment, external funding was not sought or used.
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