Diagnosis in acute abdominal pain and ongoing abdominal sepsis Kiewiet, Jordy

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Diagnosis in acute abdominal pain and ongoing abdominal sepsis
Kiewiet, J.J.S.
Publication date
2016
Document Version
Final published version
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Citation for published version (APA):
Kiewiet, J. J. S. (2016). Diagnosis in acute abdominal pain and ongoing abdominal sepsis.
[Thesis, fully internal, Universiteit van Amsterdam].
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Part 1...
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hapter
A Systematic Review
and Meta-Analysis of
Diagnostic Performance
of Imaging in Acute
Cholecystitis
J.J. S. Kiewiet1, M.M. N. Leeuwenburgh2,
S. Bipat2, P.M. M. Bossuyt3, J. Stoker2,
M.A. Boermeester1
1. Department of Surgery, Academic Medical Centre, Amsterdam,
The Netherlands
2. Department of Radiology, Academic Medical Centre, Amsterdam,
The Netherlands
3. Department of Clinical Epidemiology & Biostatistics, Academic
Medical Centre, Amsterdam, the Netherlands
radIology 2012:264;708-720.
79
1 ABSTRACT
Purpose: To update previously summarized estimates of diagnostic accuracy for acute chole-
2
cystitis and to obtain summary estimates for more recently introduced modalities.
3 Materials and Methods: A systematic search was performed in MEDLINE, EMBASE, Cochrane
Library, and CINAHL databases up to March 2011 to identify studies about evaluation of im-
aging modalities in patients who were suspected of having acute cholecystitis. Inclusion cri-
4
teria were explicit criteria for a positive test result, surgery and/or follow-up as the reference
standard, and sufficient data to construct a 2 x 2 table. Studies about evaluation of predomi-
5
nantly acalculous cholecystitis in intensive care unit patients were excluded. Bivariate ran-
dom-effects modeling was used to obtain summary estimates of sensitivity and specificity.
6
Results: Fifty-seven studies were included, with evaluation of 5859 patients. Sensitivity of
cholescintigraphy (96%; 95% confidence interval [CI]: 94%, 97%) was significantly higher
7
than sensitivity of ultrasonography (US) (81%; 95% CI: 75%, 87%) and magnetic resonance
(MR) imaging (85%; 95% CI: 66%, 95%). There were no significant differences in specificity
8
among cholescintigraphy (90%; 95% CI: 86% , 93%), US (83%; 95% CI: 74%, 89%) and MR
imaging (81%; 95% CI: 69%, 90%). Only one study about evaluation of computed tomogra-
9 phy (CT) met the inclusion criteria; the reported sensitivity was 94% (95% CI: 73%, 99%) at a
specificity of 59% (95% CI: 42%, 74%).
Conclusion: Cholescintigraphy has the highest diagnostic accuracy of all imaging modalities
in detection of acute cholecystitis. The diagnostic accuracy of US has a substantial margin of
error, comparable to that of MR imaging, while CT is still underevaluated.
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80 A Systematic Review and Meta-Analysis of…
INTRODUCTION 1
Approximately 10%–15% of adults in the Western population have gallstones. Each year, be-
tween 1% and 4% of these individuals become symptomatic.1 With a prevalence of 5%, acute
2
cholecystitis is a common entity in patients presenting at the emergency department with
acute abdominal pain.2 The condition can be life threatening and may require direct medical
intervention.3,4 The preferred treatment is a laparoscopic cholecystectomy.4,5 Timing of the 3
operation has long been debated, but through a Cochrane Library review6, the conclusion
was reached that early laparoscopic cholecystectomy is safe. Accurate and timely diagnosis
4
is essential to initiate adequate treatment. Clinical history, physical examination, and routine
laboratory tests alone result in too many unnecessary cholecystectomies and missed diagno-
5
ses.7 Therefore, imaging plays a major role in the management strategy and is performed in
a large number of patients to improve diagnostic accuracy.7
The Tokyo guidelines3 proposed diagnostic and severity criteria to standardize the diagnosis 6
and severity assessment of acute cholecystitis. According to these guidelines, a definite diag-
nosis of acute cholecystitis can be made on the basis of diagnostic criteria in two scenarios.
7
The first is based on one local sign of inflammation (Murphy sign or right upper quadrant
pain, mass, or tenderness) and one systemic sign of inflammation (fever, increased C-reactive
8
protein level, increased white blood cell count). The second set of criteria consists of imaging
findings that are characteristic for the diagnosis in patients who are clinically suspected of
having the disease. These characteristics include a thickened gallbladder wall or enlarged 9
gallbladder at ultrasonography (US), magnetic resonance (MR) imaging or computed tomog-
raphy (CT); tenderness elicited by pressing the gallbladder with the US probe (sonographic
Murphy sign); pericholecystic fluid collection at US and CT; or pericholecystic high signal
intensity at MR imaging.
In 1994, Shea et al8 reported a systematic review of imaging studies published between
1978 and 1990. In this review, they concluded that cholescintigraphy had the best sensitivity
(97%; 95% confidence interval [CI]: 96%, 98%) and specificity (90%; 95% CI: 86%, 95%) in the
detection of acute cholecystitis, whereas US had a sensitivity of 88% (95% CI: 74%, 100%) and
a specificity of 80% (95% CI: 62%, 98%).
It is uncertain whether these accuracy estimates still hold true 20 years later, given that
more accuracy studies have been published since 1990. There has also been substantial tech-
nological improvement in imaging techniques during the last 2 decades (eg, improved reso-
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lution and the use of Doppler imaging in US), and newer modalities have been introduced. h
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… Diagnostic Performance of Imaging in Acute Cholecystitis 81
There are reports that CT and MR imaging have a diagnostic2,9, but these suggestions were
1 based on studies in small series of patients or studies in highly selected patients.
The aim of this study was to update the diagnostic accuracy summary estimates for imaging
modalities described by Shea et al8, by using state-of-theart methods for the meta-analysis
2
of diagnostic accuracy studies, and to obtain precise and valid summary estimates of diag-
nostic accuracy for the more recently introduced imaging modalities. For this purpose we
3 performed a systematic review of accuracy studies with the evaluation of US, cholescintig-
raphy, CT, or MR imaging, or two or more of these modalities in the same patients who were
suspected of having acute cholecystitis.
4
5
MATERIAL AND METHODS
Search Strategy
6 We searched the MEDLINE, EMBASE, Cochrane Library, and CINAHL databases without pub-
lication date or language restrictions up to March 2011 with indexed search terms for cho-
lecystitis, US, cholescintigraphy, CT, and MR imaging. Detailed search terms are included in
7
Table E1.
8
Study Selection
All search hits were evaluated for eligibility by two reviewers (J.J.S.K. and M.M.N.L., with 4
9 and 3 years of experience, respectively) who screened titles and abstracts. Both reviewers
had experience in data extraction for retrospective and prospective studies. An article was
considered potentially eligible if US, cholescintigraphy, CT, or MR imaging was evaluated in
adult patients who were suspected of having acute cholecystitis. Full-text versions of poten-
tially eligible articles were obtained for further evaluation.
Studies were included if, in addition, all of the following inclusion criteria were met: (a)
explicit criteria were reported to define a positive imaging result; (b) surgery and/or clinical
follow-up was used as reference standard; (c) enough data were reported to extract the num-
ber of true-positive, true-negative, false-positive, and false negative results. Studies were
excluded if they were case reports or if the study population consisted of patients in an
intensive care unit. Intensive care unit patients constitute a completely different popula-
tion with a different entity (predominantly acalculous cholecystitis) compared with patients
presenting at the emergency department with acute abdominal pain who were suspected of
4
er having acute (calculous) cholecystitis.
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82 A Systematic Review and Meta-Analysis of…
The reference lists of the included studies were manually searched to identify other poten-
tially eligible articles. Disagreements in study selection between the two reviewers were 1
resolved through discussion. If no consensus could be reached, a third reviewer (S.B.) was
consulted who had previous experience in data extraction in more than 10 systematic re-
2
views or meta-analyses.
Critical Appraisal 3
The two reviewers independently extracted data from the included studies by using a struc-
tured study record form. In case of discrepancy, consensus was reached in discussion.
4
Study design, quality, and patient characteristics
5
We extracted the following study design characteristics: study period, department of the
first author, single- or multicenter study, country of origin, and criteria for selection of pa-
tients. We also extracted study group characteristics, such as the number of patients includ- 6
ed, the mean or median age and the age range of the patients, the male-to-female ratio, and
the prevalence of acute cholecystitis. The Quality Assessment of Diagnostic Accuracy Studies
7
(QUADAS) tool was used to assess the methodological quality of the included studies.10
8
Imaging characteristics.
If available, basic technical and procedural characteristics for every imaging modality and
observer experience were extracted and presented to provide descriptive information. For 9
US, the type of probe was recorded, as well as the frequency and type of scanning. For CT, the
type of scanner, section thickness, scan dose, and the use of contrast agent were recorded.
For MR imaging, the manufacturer of the MR imaging unit was noted, the magnetic field
strength, the sequences used, and the use of contrast agents. For cholescintigraphy, the type
and dose of the radiopharmaceutical and the scan interval and duration were recorded. The
criteria to classify a test result as positive for acute cholecystitis were recorded.
Reference standard
The use of surgery and/or clinical follow-up as reference standard was assessed in evaluat-
ing eligibility. Details on the proportion of patients undergoing surgery and features used
at surgery or at histopathologic analysis to diagnose acute cholecystitis were also recorded.
Furthermore, the duration and means of clinical follow-up were recorded.
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… Diagnostic Performance of Imaging in Acute Cholecystitis 83
1 Data Extraction and Analysis
Overall diagnostic accuracy
We extracted or reconstructed 2 x 2 contingency tables for each imaging modality in every
2
included study. If the researchers in a study reported data on more than one technical as-
pect of the same imaging modality, a contingency table was created for the most advanced
3 technique. If diagnostic accuracy was compared between different groups of observers, only
one contingency table for the findings by radiologists was included. Sensitivity and specific-
ity estimates were calculated from the extracted contingency tables. Individual study esti-
4
mates were plotted in receiver operating characteristic (ROC) space, to highlight covariation
between sensitivity and specificity and to explore study heterogeneity. Heterogeneity was
5
quantified with the I2 test statistic, including 95% CIs. The I2 statistic expresses the percent-
age of the total variation across studies that is caused by heterogeneity rather than chance.
6 A higher percentage indicates more heterogeneity.11,12 We used a bivariate random-effects
model to obtain summary estimates of sensitivity and specificity and corresponding 95%
CIs.13 A summary ROC curve was drawn on the basis of the between-study variance matrix
7
in the ROC space where the individual studies were plotted. To compare the sensitivity and
specificity between two modalities, we used a z test for unpaired data. Further details on
8
the bivariate model and the z test are given in Appendix E1. All statistical analyses were
performed with an electronic spreadsheet program (Excel, Microsoft Office 2003; Microsoft,
9 Redmond, Wash) and statistical software (SAS, version 9.2; SAS Institute, Cary, NC). In hy-
pothesis testing, P values of less than .05 were considered to indicate a significant difference.
Head-to-head comparison.
Studies with comparison of the diagnostic accuracy for two or more imaging modalities
were analyzed separately, because head-to-head comparisons in general offer a more valid
way of comparing imaging tests. The heterogeneity in the head-to-head comparisons was
quantified with the I2 test statistic, including 95% CIs. Individual studies were plotted in an
ROC space with connecting lines, as were summary estimates. The bivariate model was used
to obtain summary estimates and 95% CIs of sensitivity and specificity in the head-to-head
comparisons, and a z test for paired data was used in the model to compare sensitivity and
specificity. Details are in Appendix E1.
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84 A Systematic Review and Meta-Analysis of…
Heterogeneity exploration. 1
Several factors that can affect the diagnostic accuracy and cause heterogeneity were incor-
porated in the bivariate model to explore their influence on sensitivity and specificity. The
2
following factors were evaluated: study prevalence of acute cholecystitis, year of publication,
clear description of criteria for patient selection (yes or no), verification with the reference
standard for the whole or a random selection of the sample (yes or no), sufficient descrip- 3
tion of the reference standard to permit replication (yes or no), reporting of inconclusive test
results, and explanation of withdrawals from the study (yes or no). Prevalence and year of
4
publication were explored as continuous factors. We considered factors to be explanatory
for the observed heterogeneity in diagnostic accuracy if the corresponding regression coef-
5
ficients were significantly different from zero. We performed subgroup analyses to identify
factors that influence diagnostic accuracy if four or more studies with evaluation of the same
modality were included. 6
Subgroup analysis.
7
Because the meta-analysis by Shea et al8 included studies up to January 1, 1990, we per-
formed a subgroup analysis per imaging modality in which we compared the results of stud-
8
ies published before January 1, 1990, with those published after this date. In earlier studies,
cholecystolithiasis as sole criterion for a positive test result was used. Current opinion is that
several features of inflammation should be present for a positive test result to be classified 9
as such.3 Therefore, we performed a subgroup analysis of studies in which cholecystolithiasis
was used as a sole criterion as opposed to studies where several criteria that indicated cho-
lecystitis were used. Differences were evaluated with the unpaired modified z-test statistic.
RESULTS
Search Strategy and Study Selection
Figure 1 depicts study selection in a flowchart. The initial search yielded 5838 hits, with 1764
duplicate titles, resulting in 4072 titles and abstracts that were screened for eligibility. For
studies, the full text was retrieved. Of these eligible studies, 57 fulfilled the inclusion criteria,
for evaluation of 5859 patients in total14-63. No additional study was included after screening
the reference lists of included studies. Discussion with a third reviewer to reach consensus
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was needed in 46 cases for eligibility and in five cases for inclusion. h
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… Diagnostic Performance of Imaging in Acute Cholecystitis 85
1 Figure 1. Study selection flowchart
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86 A Systematic Review and Meta-Analysis of…
Figure 2. Study quality
1
2
3
4
5
6
7
The grouped bar chart displays the cumulative score of the 57 (low quality)
8
included studies for each of the 14 QUADAS questions. The proportion of the bar that is white
( ) represents that the answer to the question was ‘Yes’ (good quality), the grey bar ( ) is
‘Unclear’ and the black bar ( ) is ‘No’ 9
QUADAS Questions:
1. Was the spectrum of patients representative of the patients who will receive the test in practice?
2. Were selection criteria clearly described?
3. Is the reference standard likely to correctly classify the target condition?
4. Is the time period between surgery (histopathology) and index test short enough to be reasonably sure that the target
condition did not change between the two tests?
5. Did the whole sample or a random selection of the sample, receive verification using a reference standard of diagnosis?
6. Did patients receive the same reference standard regardless of the index test result?
7. Was the reference standard independent of the index test (i.e. the index test did not form part of the reference standard)?
8. Was the execution of the index test described in sufficient detail to permit replication of the test?
9. Was the execution of the reference standard described in sufficient detail to permit its replication?
10. Were the index test results interpreted without knowledge of the results of the reference standard?
11. Were the reference standard results interpreted without knowledge of the results of the index test?
12. Were the same clinical data available when test results were interpreted as would be available when the test is used in practice?
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13. Were uninterpretable/ intermediate test results reported? h
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… Diagnostic Performance of Imaging in Acute Cholecystitis 87