REVIEW
A detailed analysis of outcome reporting from randomisedcontrolled trials and meta-analyses of inguinal hernia repair
A. Bhangu • P. Singh • T. Pinkney •
J. M. Blazeby
Received: 10 February 2014 / Accepted: 28 July 2014
� Springer-Verlag France 2014
Abstract
Introduction Evidence is needed to justify whether
investment in an internationally agreed core outcome set
for inguinal hernia surgery is needed. This study aimed to
assess outcome reporting from randomised controlled trials
(RCTs) and meta-analyses in inguinal hernia surgery.
Methods RCTs and meta-analyses comparing surgical
technique or mesh type for primary inguinal hernia repair
were systematically identified. Verbatim details, type, fre-
quency and definition of clinician-observed and -assessed
outcomes were summarised. Patient-reported outcome
measures (PROMs) were analysed for instrument validity
and frequency of domain reporting.
Results 40 RCTs (10,810 patients) and 7 meta-analyses
(17,280 patients) were identified. No single PROM was
reported by all studies. There were 58 different clinician-
observed outcomes, with recurrence (n = 47, 100 %),
wound infection (n = 33, 70.2 %), haematoma (n = 31,
77.5 %) and seroma formation (n = 22, 46.8 %) being
most frequently reported. All studies measured patients’
views, although only 12 (30.0 %) used validated instru-
ments. The SF36 was the most commonly used multi-
dimensional valid PROM (n = 7), and a visual analogue
scale assessing pain (n = 32) was the most frequently used
unidimensional scale. Non-validated questionnaires
assessed 25 other aspects of patients’ health. Two meta-
analyses defined recurrence and three chronic pain
although neither ensured that included RCTs adhered to the
definitions.
Conclusions Outcome reporting from RCTs concerning
inguinal hernia repair is inconsistent and poorly defined,
limiting meta-analyses, which themselves do not control
for the differing definitions of assessed outcomes. This
study justifies investment in a standardised core outcome
set for inguinal hernia surgery, to improve outcome
reporting and evidence synthesis.
Keywords Hernia � Inguinal hernia � Outcome
assessment
Introduction
Hernia repair is one of the most commonly performed
surgical operations, with approximately 800,000 groin
repairs annually in the United States and 75,000 in the
United Kingdom [1, 2]. Recurrence rates have fallen with
advances in surgical technique and mesh technology, and
the advent of laparoscopic repair has brought potential
benefits of reduced pain and speedier recovery [3, 4]. This
progress has subsequently led to an era of increased focus
on methods to reduce chronic pain and improve quality of
life [4].
As a result of numerous randomised controlled trials in
hernia surgery, meta-analyses and Cochrane reviews have
been published to help surgeons and patients make deci-
sions about which operation and technique to choose [3–5].
However, the conclusions reached by these comparisons
are only valid if outcome assessment within each individ-
ual study was consistent. Although validated methods to
A. Bhangu (&) � P. Singh � T. Pinkney
West Midlands Research Collaborative, Academic Department
of Surgery, Queen Elizabeth Hospital, Room 29, 4th Floor,
Edgbaston, Birmingham B15 2TH, UK
e-mail: [email protected]
J. M. Blazeby
Centre for Surgical Research School of Social and Community
Medicine, University of Bristol and University Hospitals Bristol
NHS Foundation Trust, Bristol, UK
123
Hernia
DOI 10.1007/s10029-014-1299-4
record surgical complications exist (such as the Clavien–
Dindo score [6]), the key post-operative outcomes fol-
lowing hernia repair require more detailed and specific
assessment. Short- and long-term outcomes including ser-
oma, recurrence, post-operative pain and quality of life are
common to all abdominal wall hernia repairs. Whilst there
have been previous attempts at standardisation of definition
and assessment of complications following hernia surgery,
including the inguinal pain questionnaire [7], widespread
uptake and standardisation have yet to occur.
CONSORT guidelines suggest reporting of all out-
comes, irrespective of magnitude of effect size and stan-
dardisation of outcomes from randomised trials prevents
outcome reporting bias [8]. A formal assessment of the
current state of outcome reporting from hernia trials is
lacking. The aim of this paper, therefore, was to undertake
an in-depth analysis of outcome reporting from inguinal
hernia surgery. This would provide evidence to justify
whether investment in an internationally agreed core out-
come set (an agreed set of outcomes to be reported in all
studies) for hernia surgery is justified.
Methods
Data sources and search strategy
This study was designed to test the hypothesis that out-
come reporting for RCTs in inguinal hernia surgery is
inconsistent. A systematic search of OVID SP version of
MEDLINE, Pubmed, the Cochrane Central Register for
Controlled Trials, Clinicaltrials.gov and the DARE
(Database of Abstracts of Reviews of Effects) database
was performed for published studies reporting outcomes
from randomised controlled trials or meta-analyses of
inguinal hernia surgery. Only studies published during
01/01/2007 and 31/12/2011 were included. This starting
date represents the modern clinical trials era, and allows
for an analysis of current design and outcome reporting
without contamination from older trials. The search was
performed independently by two researchers. The search
strategies used are presented in Table 1. A manual
search of reference lists from systematic reviews and
meta-analyses was undertaken to further identify ran-
domised trials of potential interest. Abstracts and con-
ference proceedings were excluded because of the high
probability of incomplete data. Citations were collated
with EndNote Reference Manager (Version X4, Thom-
son Reuters) and duplicates removed. The study protocol
was registered with the Core Outcome Measures in
Effectiveness Trials (COMET) initiative [9].
Inclusion and exclusion criteria
Inclusion criteria
Randomised controlled trials or meta-analyses of patients
with primary inguinal hernias undergoing elective repair
where at least one clinical outcome and/or one validated
patient-reported outcome measure (PROM) was reported
were included. Only studies relating to surgical technique
(rather than anaesthetic or analgesic technique) were
included, with either unilateral or bilateral hernia.
Table 1 Search strategies
Inguinal hernia 1. Exp Hernia, Inguinal/
Surgery 1. Exp Specialties, Surgical/
2. surg$.tw
3. Operat$.tw
4. or/1–3
Randomised
controlled trials
1. Randomised controlled trial.pt
2. Controlled clinical trial.pt
3. Randomised controlled trial.sh
4. Random allocation.sh
5. Double blind method.sh
6. Single blind method.sh
7. Or/1–6
8. Exp animals/not human/
9. 7 not 8
10. Clinical trial.pt
11. Exp clinical trial/
12. (clinical adj trial$).tw
13. ((singl$ or doubl$ or treb$ or tripl$) adj
(blind$3 or mask$3)).tw
14. Random.tw
15. Or/10–14
16. 15 not 8
17. 16 not 9
18. Case report.tw
19. Letter/
20. Historical article/
21. Or/18-20
22. 21 not 8
23. 22 not 9
24. 9 or 17
25. 24 not 23
Adapted versions of the strategy were used in Pubmed and the
Cochrane Central Register for Controlled Trials (not shown). Results
for ‘inguinal hernia’ were combined using ‘AND’ with search terms
for ‘surgery’ ‘AND’ ‘randomised. Search terms for ‘inguinal hernia’
and ‘met-analysis’ were combined in the OVID SP version of
MEDLINE, Pubmed and the DARE database to identify relevant
meta-analyses
Hernia
123
Exclusion criteria
The following exclusion criteria were applied: trials
including ventral wall, femoral, incisional, parastomal or
recurrent hernias; trials comparing non-surgical tech-
niques (e.g. methods of analgesia); trials including
strangulated or other emergency repair; all non-ran-
domised study designs. Where there was overlap
between two studies, the study that contained the larger
number of patients was included. If an earlier published
study provided additional outcomes (e.g. trial method-
ology or short-term outcomes prior to a report of long-
term outcomes), data from the earlier study were
extracted and entered as part the latter study.
Data extraction and presentation
Two authors extracted data independently. Discrepancies
were resolved by re-examination of the relevant study until
consensus was achieved.
Study design
Information extracted relative to study design included: number
of surgeons/centres, number of patients included, number of
hernias randomised, blinding methodology, comparative arms
and what was the primary outcome and a complete list of all
secondary outcomes. Provision for blinding of the patient and/
or post-operative assessor was recorded. For RCTs, study
design was assessed using the Cochrane Collaboration’s tool
for assessment of risk of bias. This tool covers six domains:
selection bias, performance bias, detection bias, attrition bias,
reporting bias, and other bias. Each domain was scored as a
high, low or unclear risk of bias by two authors independently;
disagreement was settled by consensus discussion. Studies with
poor, uncertain or unclear methods of randomisation were
considered to be at high risk of bias. Additional, pre-specified
sources of bias were inadequate descriptions of clinician
blinding during outcome assessment, patient blinding to pro-
cedure, allocation concealment and incomplete outcome
reporting based on pre-specified aims.
Fig. 1 Flowchart of included
studies
Hernia
123
Surgical intervention
Comparative arms were classified as follows: (1) mesh
type: comparison between types of mesh, e.g. lightweight
versus heavyweight, Lichtenstein versus mesh plugs; (2)
mesh fixation: comparison between types of mesh fixation,
sutures versus glue; (3) mesh position: comparison between
different layers of mesh position, e.g. sublay versus onlay;
(4) laparoscopic versus open approaches; (5) fixation types:
comparison between two different techniques for hernia
repair, e.g. mesh versus darn, Shouldice versus Bassini
repair.
Clinical outcomes
The presence of a pre-stated primary clinical outcome and
the total number of reported primary and secondary out-
comes was recorded. For each stated clinical outcome,
provision of a definition, position of the outcome assessor
and use of unvalidated assessment domains (e.g. ‘‘presence
of sensations of dragging’’) were determined. The number
of times a single specific outcome measure was only
reported by one study (‘‘single outcome reported by single
study’’) was noted.
Patient-reported outcomes
Details of reporting for all validated and unvalidated
PROMs were recorded, including timing of assessment,
completeness of assessment at each time point and provi-
sion of definitions. Provision for measurement of quality of
life using generic or disease-specific tools was recorded.
Assessment of meta-analysis
The quality tool used for assessment of conduct and/or
reporting of included trials within individual meta-analysis
was recorded. For each domain assessed, the provision of a
definition by the meta-analysis and whether individual
RCTs were assessed for compliance with this definition
was recorded.
Results
Study demographics
40 RCTs (10,810 patients, range 22–1,512) and seven
meta-analyses (17,280 patients, range 772–5,398) were
included in the final analysis (Fig. 1). Study demographics
of RCTs and meta-analyses, including number of surgeons/
centres, laterality, trial demographics, and primary out-
comes, are shown in Table 2.
Risk of bias assessments between RCTs
Outcome of risk of bias assessments for the included RCTs,
based on the Cochrane Collaboration’s tool, is shown in
Fig. 2. The highest area of bias was for absent or inade-
quate description of random sequence generation (high or
unclear risk of bias, 26 studies). Blinding of assessors for at
least one outcome was stipulated for 19 studies, was not
presented for 11 and was unstated for a further 11 studies.
Table 2 Study parameters from 40 included randomised controlled
trials and 7 meta-analyses
Group Characteristic Number of studies
(%)
RCT
Number of
surgeons
1 20 (50.0)
2–10 5 (12.5)
25–50 2 (5.0)
Unstated/unclear 13 (32.5)
Number of
centres
1 17 (42.5)
2–10 10 (25.0)
11–15 3 (7.5)
Unstated/unclear 10 (25.0)
Laterality Unilateral 27 (67.5)
Bilateral 12 (30.0)
Unstated/unclear 1 (2.5)
Number of trial
arms
2 27 (67.5)
3–5 13 (32.5)
Trial type Mesh type 14 (35.0)
Laparoscopic vs open 9 (22.5)
Repair type 9 (22.5)
Mesh fixation 7 (17.5)
Laparoscopic approach 1 (2.5)
Primary outcome Pain 12 (30.0)
Recurrence 8 (20.0)
Fertility 2 (5.0)
Short-term
convalescence
1 (2.5)
SF36 subscale on bodily
pain
1 (2.5)
Operation time 1 (2.5)
Unclear 3 (7.5)
[3 primary outcomes 3 (7.5)
2 primary outcomes 9 (22.5)
Meta-analysis
Number of
studies
0–9 4 (57.1)
10? 3 (42.9)
Trial type Mesh type 3 (42.9)
Mesh fixation 2 (28.6)
Repair type 2 (28.6)
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123
There was additional high risk of bias for allocation con-
cealment and blinding of participants/personnel.
Risk of bias assessments within meta-analyses
Three meta-analyses used the Cochrane Collaboration’s
tool for assessment of risk of bias [10–12], one used the
Cochrane Collaboration’s tool and the Jadad scale [13], one
study the Jadad scale alone [14], and two made no risk of
bias assessment [14, 15].
Clinician-reported outcomes from RCTs
A total of three different intra-operative measures, 10 dif-
ferent intra-operative complications, and 50 different post-
operative measures were reported from the 40 RCTs
(Table 3). The most common intra-operative measure
reported was operating time (35 studies, 87.5 %). The most
common intra-operative complication reported was nerve
injury (12 studies, 30.0 %). Recurrence was the only CRO
reported by all studies (40 studies); wound infection (32
studies) and haematoma (31 studies) were the second and
third most commonly reported post-operative CROs.
Corresponding definitions of CROs are shown in
Table 4. Half of studies provided guidance for a clinical
definition of hernia recurrence (20/40). A specific
description of the examination technique to detect recur-
rence was provided from 6 studies, with 14 accepting the
unspecified opinion of the clinicians; in 20 studies, the
method for determination of recurrence was unstated. A
blinded assessor was stipulated by 16 studies (40.0 %); the
remainder were either unblinded (1, 2.5 %) or unclear (23,
57.5 %). Supplemental imaging to identify or confirm
recurrence was used in seven studies, with four stipulating
routine ultrasound scan in all patients, and three selective
imaging only when indicated by clinical need. The most
common time point for determination of recurrence was
1 year post-operatively (Fig. 3).
A definition of wound infection was recorded by three
studies [16–18], with only one using the validated and
widely accepted criteria recommended by the Centre for
Disease Control [19]. Seroma and haematoma were defined
by one study each.
Clinician-reported outcomes from meta-analyses
Two different intra-operative measures and 18 different
post-operative measures were reported from the seven
meta-analyses. Recurrence was assessed by all studies
(Table 3), with a definition being provided by two
(Table 4). One of these studies compared this definition to
those provided from individual studies, but it is unclear
what influence this had on further analysis (no direct
statement made) and thus should still be considered at risk
of bias. There were no definitions for haematoma, seroma
or wound infection from any meta-analysis and no quality
control as to pooling of these outcomes according to
common assessment criteria.
Fig. 2 Distribution of low,
unclear and high risk of bias
derived from the Cochrane
Collaboration’s risk of bias tool,
applied to the 41 included RCTs
Hernia
123
Patient-reported outcome measures from RCTs
All studies made at least one validated or unvalidated
attempt to assess patients’ views. Twelve studies used six
Table 3 Clinician-reported outcomes from RCTs and meta-analyses
Number of
RCTS
(n = 40 %)
Number of
meta-analyses
(n = 7 %)
Intra-operative measures
Operating time (reported in
minutes)
35 (87.5) 6 (85.7)
Length of stay (reported in days) 21 (52.5) 3 (42.9)
Blood loss (reported in millilitres) 3 (7.5)
Intra-operative complications
Nerve injury 12 (30.0)
Bleeding 7 (17.5)
Laparoscopic conversion 5 (12.5)
Bladder injury 3 (7.5)
Anaesthetic complication 3 (7.5)
Re-operation within 24 h 3 (7.5)
Ductus deferens damage 2 (5.0)
Technical problem 2 (5.0)
Single outcome cited by single
studya
2 (5.0)
Post-operative outcomes
Recurrence 40 (100.0) 7 (100)
Wound/local complications
Wound infection 32 (80.0) 3 (42.9)
Haematoma 31 (77.5) 2 (28.6)
Seroma 21 (52.5) 5 (71.4)
Single outcome cited by single
study
5 (12.5) 4 (57.1)
Redness of wound or wound
oedema
4 (10.0)
Combined haematoma/seroma 3 (7.5)
Wound dehiscence 3 (7.5)
Urinary/testicular
Urinary retention 19 (47.5) 2 (28.6)
Testicular atrophy 10 (25.0) 5 (71.4)
Single outcome cited by single
studya
10 (25.0) 1 (14.3)
Scrotal swelling/oedema 3 (7.5) 2 (28.6)
Testicular discomfort 3 (7.5)
Urinary tract discomfort 3 (7.5)
Medical/other
Single outcome cited by single
studya
19 (47.5) 4 (57.1)
Mortality 2 (5.0)
Unexpected readmission 2 (5.0)
Healthcare costs 2 (5.0) 2 (28.6)
Functional index score (climbing
stairs, squatting, rising from a
bed)
1 (2.5)
a The number of times a specific outcome which was only reported
by one study
Table 4 Definitions and assessments of outcomes where assessment
variability may exist between assessment techniques
Definition of recurrence (RCT)
Unstated [16, 21, 22, 34–50] 20
Unspecified physical examination [17, 26, 51–62] 14
‘‘Palpable, reducible lump in the treated groin, with or without
symptoms’’ [63]
1
‘‘Direct clinical examination with the presence of bulging in
the repaired inguinal region when the patient coughed’’ [18]
1
‘‘Bulge or weakness in the operative area exacerbated by a
Valsalva manoeuvre and palpable outside the external ring’’
[64]
1
‘‘Bulge in the operated groin when standing or straining’’ [65] 1
‘‘Presence of an expansile cough impulse’’ [66] 1
‘‘Reappearance of a reducible bulge at or around the hernia site
with a positive cough impulse’’ [67]
1
Clinician making assessment of recurrence (RCT)
Unclear [16, 22, 34, 35, 38, 41–44, 47, 49–51, 54, 56, 59, 61,
62]
18
Unblinded surgeon [63] 1
Blinded surgeon [18, 21, 36, 37, 39, 40, 45, 46, 48, 52, 55, 57,
58, 60, 64, 66]
16
Surgeon, blinding unclear [17, 26, 53, 65, 67] 5
Use of supplemental imaging (RCT)
Routine USS [26, 60, 61, 67] 4
Selective USS [64] 1
Selective CT [67] 1
Selective herniography [65] 1
Definition of recurrence (meta-analysis)
Clinically manifest bulge or a protrusion exacerbated by a
Valsalva manoeuver in the operated groin
1
Clinically manifest bulge or protrusion by a Valsalva
manoeuvre in the operated groin. The assessor could be a
surgeon, physician or the patient
1
Wound infection (RCT)
‘‘Purulent discharge or the presence of microorganisms which
were present in culture studies in any discharge’’ [16]
1
Light-erythema present, medium-pus present, severe-pus and
fever [17]
1
Centre for Disease Control definition [18] 1
Not provided [26, 34–38, 40–45, 47, 48, 51–60, 63, 64, 66, 67] 30
Haematoma (RCT)
None [16–18, 22, 26, 34–39, 41–49, 51–56, 58, 64, 65, 67] 30
[50 cm3 on USS [66] 1
Seroma (RCT)
None [16–18, 22, 34–39, 51–56, 64, 65] 20
‘‘Non-tender irreducible hemispherical swelling with a
fluctuant or firm consistency at the hernia site’’ [67]
1
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123
validated tools to specifically assess QoL, with the SF36 as
the most commonly used multi-dimensional valid PROM
(n = 7). Non-validated questionnaires assessed 25 other
aspects of patients’ reported health.
Post-operative pain was assessed in 39 studies (97.5 %),
with a visual analogue scale being the most commonly
used tool (32 studies, 80.0 %, Table 5). The most common
time point for assessment was 1–8 weeks post-operatively,
although frequent assessments were also made at 0–48 h,
3–6 months and 1 year (Fig. 3). The following dedicated
tools were used to further assess pain: post-herniorrhaphy
pain questionnaire [20]; McGill pain Questionnaire [21];
Inguinal Pain Questionnaire [22]; Cunningham classifica-
tion of post-herniorrhaphy pain [21]. The time points at
which pain was assessed are shown in Fig. 3.
Six different timing cut offs for the onset of chronic pain
were reported from 18 studies (Table 5). Patient-reported
recurrence was assessed in seven studies, through tele-
phone questionnaire, postal questionnaire, instructions to
report any recurrence, and an unstated method in one study
(Table 5).
Patient-reported outcome measures from meta-analyses
Meta-analysis was performed for eight different unvali-
dated PROMs from the seven studies (Table 5). Three
studies meta-analysed post-operative pain and six studies
chronic pain, which was defined by three studies as
occurrence [3 months after surgery and was undefined in
three studies.
Discussion
This study has analysed outcome reporting from a large
number of recently published randomised controlled trials
and meta-analyses concerning primary inguinal hernia
surgery. The key findings include an absence of stand-
ardised inclusion, definition, assessment methods and
assessment times of the key primary and secondary out-
comes. This affects the validity of comparisons made in
meta-analyses and for the practicing surgeon comparing
outcomes from different trials. It may also have led to
under-reporting of important outcomes, including recur-
rence, wound infection and the incidence of pain and
other outcomes of importance to patients. The included
meta-analyses suffered from a similar lack of definitions,
and where definitions were provided, the meta-analyses
generally failed to ensure that the included studies
adhered to them. This study provides justification for
urgent investment in a core outcome set applicable to
inguinal hernia surgery. This should be developed and
validated with key stakeholders using formal methodol-
ogy, beyond expert recommendations alone, to improve
quality of outcome reporting.
The COMET group are working to facilitate promotion
and development of core outcome sets for trials [9]. This
study strongly supports an outcome set for primary inguinal
hernia surgery, which should involve clinician-observed
and patient-reported outcome measures, with clear time
points for assessment. Short-term outcomes should include
intra-operative details and early post-operative outcomes,
Fig. 3 Time points for
assessment of recurrence and
pain
Hernia
123
including pain and return to activity. Long-term outcomes
should include recurrence, chronic pain and quality of life.
Blinding of outcome assessment was also problematic in
the included studies from this review, which introduces risk
of bias in randomised controlled trials. Blinding of both
patients and post-operative assessors should be built into
trial protocols wherever possible. Furthermore, meta-anal-
yses should ensure that their included trials adhere to these
standards, allowing unbiased pooling and comparison of
outcomes within and between RCTs.
For many years, recurrence has been the key endpoint of
inguinal hernia trials. More recently, the stable low rates
have meant that more importance has been placed on
quality of life measures that are of increasing relevance to
patients, including pain, adverse events and other important
aspects of quality of life. Nonetheless, ensuring low rates
of recurrence for new techniques remains important. Six-
teen studies still did not define recurrence and a further 15
described an unspecified physical examination, both of
which may introduce bias due to differing assessment
methods. The remaining six studies made some attempt to
standardise examination technique, although the lack of
uniformity between them may limit meta-analysis. In par-
ticular the timing of reporting rates of recurrence was often
missing or very early—whilst a longer term assessment is
required to ensure accurate measurement.
The use of imaging to augment clinical examination
may provide a means of standardising detection and
reporting of recurrence rates. If validated, early imaging
may act as an early surrogate of late symptomatic hernia
and allow early delivery of hernia-related trials without the
delay needed for long-term follow-up [23]. In this review,
ultrasound was the most commonly used additional imag-
ing modality, with little assessment of CT. These methods
deserve further validation as markers of recurrence.
Current research to reduce the incidence of both post-
operative and chronic pain includes lightweight versus
heavyweight mesh types, tack fixation, glue fixation and
self-adhesive meshes. This stems from the uncertain and
possibly mixed aetiology of chronic pain, which may affect
between 0 and 40 % of patients following surgery and can
lead to long-term functional impairment [24]. The varying
definitions used for pain, and particularly chronic pain, add
further potential variation to its assessment. Visual Ana-
logue Scales were the most widely used tool to assess pain,
although they lack specificity to hernia-specific surgery.
The Inguinal Pain Questionnaire has been validated for use
following groin hernia repair [25], but it is not yet widely
in use. The degree of an individual patient’s pain is likely
to vary and so pre-operative assessments may be important
to detect changes, rather than rely on absolute post-oper-
ative values.
Table 5 Patient-reported outcomes from RCTs and meta-analyses
Domain Number ofRCTS(n = 40 %)
Number of meta-analyses (n = 7%)
Quality of life
Validated assessment tool used
SF36 Health Survey 7 (17.5)
SHS 1 (2.5)
SF12 1 (2.5)
Inguinal pain questionnaire 1 (2.5)
McGill pain questionnaire 1 (2.5)
EuroQol EQ-5D 1 (2.5)
Pre-operative QoL assessmentmade
9 (22.5)
Unvalidated questions/questionnaires/tools
Disturbance of daily activities/return to work
23 (57.5) 4 (57.1)
Single outcome cited by singlestudya
16 (40.0) 4 (57.1)
Dragging/foreign bodysensation
8 (20.0) 2 (28.6)
Numbness 8 (20.0) 2 (28.6)
Return to sports 5 (12.5)
Persistent pain 4 (10.0)
Satisfaction 3 (7.5) 1 (14.3)
Sexual activity 3 (7.5)
Intermittent pain 2 (5.0)
Intensity of pain 2 (5.0)
Patient-reported recurrence 7 (10.0)
Questionnaire 3 (7.5)
Telephone 2 (5.0)
Patient asked to report anyrecurrence
1 (2.5)
Unstated 1 (2.5)
Post-operative pain 39 (97.5) 3 (42.9)
Method of assessment
Visual analogue scale 32 (80.0) 3 (42.9)
Analgesic consumption 20 (50.0) 1 (14.3)
Verbal scale 3 (7.5)
Unvalidated painquestionnaire
3 (7.5)
Inguinal pain questionnaire 1 (2.5)
McGill pain questionnaire 1 (2.5)
Post-herniorrhaphy painscale
1 (2.5) 1 (14.3)
Cunningham classification ofpost-herniorrhaphy pain
1 (2.5)
Definition of chronic pain 18 (45.0) 6 (85.7)
[6 months 2 (5.0)
[3 years 1 (2.5)
[3 months 5 (12.5) 3 (42.9)
[2 years 1 (2.5)
[2 months 1 (2.5)
[12 months 8 (20.0)
a The number of times a specific outcome which was only reportedby one study
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Chronic pain and quality of life are closely related
[26], although their definition and assessment are often
separated, partly due to a lack of hernia-specific assess-
ment tools. When comparing different surgical tech-
niques, QoL is an important patient-centred endpoint, as
the importance patients place on certain outcomes may
differ from the surgeons’ perspective. In the present
review, 12 studies made an assessment of QoL using a
validated tool. Whilst tools such as EuroQol, SF12 and
the Short Health Scale evaluate health in multiple
domains and across multiple populations, they may lack
sensitivity to disease-specific states, including outcome
from hernia surgery, which has a specific complication
profile. Kaarafani et al. [27] described methodology to
classify complications following ventral incisional her-
niorrhaphy. Their approach allows for direct comparison
of procedures with different complication profiles, al-
thoughthe views of patients as to the importance of each
specific complication requires further research. Due to the
unique profile of complications following hernia surgery
and the importance of chronic pain, development of a
hernia-specific QoL tool is needed, using a process that
includes patient involvement.
Surgical site infection was frequently assessed, but only
three studies provided a standardised definition. Despite the
frequency of SSI, differing definitions from surgical studies
are common. Bruce et al. [28] performed a systematic
review of prospective studies assessing wound infection,
finding 41 different definitions from 112 studies. Only one
study used the developed definition from the Centre for
Disease Control [29]; universal adoption of these defini-
tions would move towards improved standardisation.
Other studies have identified the variability in defini-
tions and outcome assessment from surgical trials in dif-
ferent health states. A systematic review of anastomotic
leak after gastrointestinal surgery found 56 separate defi-
nitions from 97 studies [30]. A review of 122 studies of
oesophageal cancer surgery found 22 different descriptions
of anastomotic leak, with further variation in the reporting
of complications and mortality [31]. Wide variation in
definitions of overall survival and wound infection fol-
lowing colorectal cancer surgery has also recently been
identified [32]. It is known that reporting only a subset of
originally recorded outcomes for publication on the basis
of results introduces reporting bias [33]. This has led to the
development of core outcome sets for defined conditions,
derived from expert groups and patients stakeholders.
Conclusion
Outcome reporting from RCTs concerning inguinal hernia
repair is inconsistent and poorly defined, which may lead to
under-reporting of outcomes. This limits meta-analyses,
which themselves did not control for the differing defini-
tions of assessed outcomes. This study supports investment
in an internationally standardised core outcome set, to
improve outcome reporting in inguinal hernia surgery.
Future meta-analyses should ensure that outcomes from
included studies adhere to controlled definitions.
Conflict of interest AB declares no conflict of interest.
PS declares no conflict of interest.
TP declares no conflict of interest.
JMB declares no conflict of interest.
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