Evidence Based Medicine on FHIR Implementation Guide
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Evidence Based Medicine on FHIR Implementation Guide, published by HL7 International / Clinical Decision Support. This guide is not an authorized publication; it is the continuous build for version 1.0.0-ballot built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/ebm/ and changes regularly. See the Directory of published versions

: ComparativeEvidence: All-cause mortality effect of bariatric surgery in 2022 meta-analysis - XML Representation

Active as of 2022-09-19

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<Evidence xmlns="http://hl7.org/fhir">
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  <meta>
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    <lastUpdated value="2023-12-08T16:33:14.612Z"/>
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  <text>
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    <div xmlns="http://www.w3.org/1999/xhtml"><p><b>Generated Narrative: Evidence</b><a name="49328"> </a><a name="hc49328"> </a></p><div style="display: inline-block; background-color: #d9e0e7; padding: 6px; margin: 4px; border: 1px solid #8da1b4; border-radius: 5px; line-height: 60%"><p style="margin-bottom: 0px">ResourceEvidence &quot;49328&quot; Version &quot;25&quot; Updated &quot;2023-12-08 16:33:14+0000&quot; </p><p style="margin-bottom: 0px">Profiles: <a href="StructureDefinition-comparative-evidence.html">ComparativeEvidence</a>, <a href="StructureDefinition-evidence-synthesis-evidence.html">EvidenceSynthesisEvidence</a></p></div><p><b>url</b>: <code>https://fevir.net/resources/Evidence/49328</code></p><p><b>identifier</b>: FEvIR Object Identifier/49328</p><p><b>version</b>: 1.0.0-ballot</p><p><b>name</b>: AllCauseMortality2022metaAnalysis</p><p><b>title</b>: ComparativeEvidence: All-cause mortality effect of bariatric surgery in 2022 meta-analysis</p><p><b>status</b>: active</p><p><b>date</b>: 2022-09-19 21:27:50+0000</p><p><b>publisher</b>: HL7 International / Clinical Decision Support</p><p><b>contact</b>: HL7 International / Clinical Decision Support: <a href="http://www.hl7.org/Special/committees/dss">http://www.hl7.org/Special/committees/dss</a></p><p><b>author</b>: Brian S. Alper: </p><h3>UseContexts</h3><table class="grid"><tr><td style="display: none">-</td><td><b>Code</b></td><td><b>Value[x]</b></td></tr><tr><td style="display: none">*</td><td>Evidence Communication (Details: Evidence Based Medicine on FHIR Implementation Guide Code System code evidence-communication = 'Evidence Communication', stated as 'Evidence Communication')</td><td>ComparativeEvidence <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="CodeSystem-179423.html">Evidence Based Medicine on FHIR Implementation Guide Code System</a>#ComparativeEvidence)</span></td></tr><tr><td style="display: none">*</td><td>Evidence Communication (Details: Evidence Based Medicine on FHIR Implementation Guide Code System code evidence-communication = 'Evidence Communication', stated as 'Evidence Communication')</td><td>EvidenceSynthesisEvidence <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="CodeSystem-179423.html">Evidence Based Medicine on FHIR Implementation Guide Code System</a>#EvidenceSynthesisEvidence)</span></td></tr><tr><td style="display: none">*</td><td>Evidence Communication (Details: Evidence Based Medicine on FHIR Implementation Guide Code System code evidence-communication = 'Evidence Communication', stated as 'Evidence Communication')</td><td>OutcomeMeasureEvidence <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="CodeSystem-179423.html">Evidence Based Medicine on FHIR Implementation Guide Code System</a>#OutcomeMeasureEvidence)</span></td></tr></table><p><b>copyright</b>: https://creativecommons.org/licenses/by-nc-sa/4.0/</p><blockquote><p><b>relatedArtifact</b></p><p><b>type</b>: derived-from</p><p><b>label</b>: data source</p><p><b>citation</b>: Bariatric surgery and cardiovascular disease: a systematic review and meta-analysis [Journal Article]. Contributors: van Veldhuisen SL, Gorter TM, van Woerden G, de Boer RA, Rienstra M, Hazebroek EJ, van Veldhuisen DJ. In: European heart journal, PMID 35243488. Published March 04, 2022. Available at: https://pubmed.ncbi.nlm.nih.gov/35243488/.</p><blockquote><p><b>document</b></p></blockquote></blockquote><blockquote><p><b>relatedArtifact</b></p><p><b>type</b>: supported-with</p><p><b>classifier</b>: Citation Resource for the original article <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> ()</span></p><p><b>display</b>: Citation Resource for 2022 Systematic Review of bariatric surgery mortality effect - PMID 35243488</p><p><b>resourceReference</b>: <a href="Citation-33400.html">Citation/33400: StudyCitation: 2022 Systematic Review of bariatric surgery mortality effect 35243488</a></p></blockquote><blockquote><p><b>relatedArtifact</b></p><p><b>type</b>: cite-as</p><p><b>citation</b>: ComparativeEvidence: All-cause mortality effect of bariatric surgery in 2022 meta-analysis [Evidence]. Contributors: Brian S. Alper [Authors/Creators]. In: Fast Evidence Interoperability Resources (FEvIR) Platform, FOI 49328. Revised 2022-09-19. Available at: https://fevir.net/resources/Evidence/49328. Computable resource at: https://fevir.net/resources/Evidence/49328.</p></blockquote><p><b>description</b>: effect estimate for bariatric surgery on all-cause mortality pooled hazard ratio (HR) 0.55 (95% confidence interval 0.49 to 0.62; P &lt; 0.001 vs. controls) in meta-analysis of 21 cohort studies with 133,524 patients after bariatric surgery and 263,478 obese controls</p><p><b>assertion</b>: The present systematic review and meta-analysis suggests that bariatric surgery is associated with reduced all-cause and CV mortality.</p><blockquote><p><b>variableDefinition</b></p><p><b>VariableDefinitionVariableRoleCode</b>: population</p><p><b>description</b>: obese, adult (age ≥18 years old) patients *NOTE: note.text is used artificially to support the EBMonFHIR Implementation Guide and the following content would more properly be found in a note.text element:* Studies were considered eligible if they were designed to study outcomes in obese patients who underwent a weight-loss surgical intervention in comparison with an age, sex, and BMI matched control group who did not undergo a weight-loss surgical intervention. We searched for randomized controlled trials, prospective or retrospective longitudinal cohort studies, and case–control studies. For the control group, all non-surgical treatment options for obesity (e.g. intensive lifestyle intervention, standard of care, or no specific therapy) were accepted. Studies were excluded if (i) patients were not matched for age, sex, and BMI; (ii) the presence of one or more outcome parameters of interest (e.g. HF, AF, coronary artery disease) was required for inclusion; or (iii) if study groups were not representative in relation to the general population of patients with obesity (e.g. patients could only be included in the presence of a specific comorbidity, for instance, end-stage renal disease). The third criterium did not apply to Type 2 diabetes, thus studies that only included patients with Type 2 diabetes could be eligible for inclusion.</p><p><b>note</b>: population</p><p><b>variableRole</b>: Use extension:variableRoleCode instead. <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://terminology.hl7.org/5.5.0/CodeSystem-variable-role.html">EvidenceVariableRole</a>#population &quot;population&quot;)</span></p><p><b>intended</b>: <a href="Group-171819.html">Group/171819: StudyEligibilityCriteria: Obese patients ≥ 18 years old</a> &quot;StudyEligibilityCriteria_Obese_patients_18_years_old&quot;</p></blockquote><blockquote><p><b>variableDefinition</b></p><p><b>VariableDefinitionVariableRoleCode</b>: exposure</p><p><b>VariableDefinitionComparatorCategory</b>: no bariatric surgery</p><p><b>description</b>: comparison groups of bariatric surgery vs. no bariatric surgery *NOTE: note.text is used artificially to support the EBMonFHIR Implementation Guide and the following content would more properly be found in a note.text element:* As the control group (observed reference exposure) was defined differently in each study, the intended reference exposure is described as the absence of the intended exposure (Bariatric Surgery).</p><p><b>note</b>: exposure</p><p><b>variableRole</b>: Use extension:variableRoleCode instead. <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://terminology.hl7.org/5.5.0/CodeSystem-variable-role.html">EvidenceVariableRole</a>#exposure &quot;exposure&quot;)</span></p><p><b>intended</b>: <a href="EvidenceVariable-172427.html">EvidenceVariable/172427: GroupAssignment: Bariatric Surgery vs. no bariatric surgery</a> &quot;GroupAssignment_Bariatric_Surgery_vs_no_bariatric_surgery&quot;</p></blockquote><blockquote><p><b>variableDefinition</b></p><p><b>VariableDefinitionVariableRoleCode</b>: outcome</p><p><b>description</b>: All-cause mortality *NOTE: note.text is used artificially to support the EBMonFHIR Implementation Guide and the following content would more properly be found in a note.text element:* The observed element can reference an EvidenceVariable Resource that defines the outcome measured through structured characteristics. For example, “Mean difference in HbA1c at 12 months” or “Mean difference in HbA1c at end of study”. The structured characteristics can be references to the Evidence instances for each of the included studies, in which case this is a direct link to the dataset used for analysis. The intended element can reference an EvidenceVariable Resource that expresses the outcome intended for evidence application through structured characteristics. The structured characteristics could be used to express the SR eligibility criteria for study outcomes (as a subset of eligibility criteria for studies).</p><p><b>note</b>: outcome</p><p><b>variableRole</b>: Use extension:variableRoleCode instead. <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://terminology.hl7.org/5.5.0/CodeSystem-variable-role.html">EvidenceVariableRole</a>#measuredVariable &quot;measured variable&quot;)</span></p><p><b>observed</b>: <span>: We searched for randomized controlled trials, prospective or retrospective longitudinal cohort studies, and case–control studies. For the control group, all non-surgical treatment options for obesity (e.g. intensive lifestyle intervention, standard of care, or no specific therapy) were accepted. Studies were excluded if (i) patients were not matched for age, sex, and BMI; (ii) the presence of one or more outcome parameters of interest (e.g. HF, AF, coronary artery disease) was required for inclusion; or (iii) if study groups were not representative in relation to the general population of patients with obesity (e.g. patients could only be included in the presence of a specific comorbidity, for instance, end-stage renal disease). The third criterium did not apply to Type 2 diabetes, thus studies that only included patients with Type 2 diabetes could be eligible for inclusion.</span></p><p><b>intended</b>: <a href="EvidenceVariable-49217.html">EvidenceVariable/49217: OutcomeVariable: All-cause mortality</a> &quot;OutcomeVariable_All_cause_mortality&quot;</p></blockquote><p><b>synthesisType</b>: summary data meta-analysis <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (StatisticSynthesisType[3.1.0]#std-MA)</span></p><p><b>studyDesign</b>: Observational research <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://hl7.org/fhir/R5/codesystem-study-design.html">Study Design[5.0.0-cibuild]</a>#SEVCO:01002)</span>, Parallel cohort design <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://hl7.org/fhir/R5/codesystem-study-design.html">Study Design[5.0.0-cibuild]</a>#SEVCO:01011)</span>, Matching for comparison <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://hl7.org/fhir/R5/codesystem-study-design.html">Study Design[5.0.0-cibuild]</a>#SEVCO:01014)</span></p><blockquote><p><b>statistic</b></p><p><b>description</b>: pooled hazard ratio (HR) 0.55 (95% confidence interval 0.49 to 0.62; P &lt; 0.001 vs. controls) in meta-analysis of 21 cohort studies with 133,524 patients after bariatric surgery and 263,478 obese controls</p><p><b>note</b>: heterogeneity: Tau2 = 0.06; Chi2 = 105.14; df = 23 (P &lt; 0.00001); I2 = 78%, test for overall effect z = 9.41 (p &lt; 0.00001)</p><p><b>statisticType</b>: Hazard Ratio <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://terminology.hl7.org/5.5.0/CodeSystem-statistic-type.html">StatisticStatisticType</a>#C93150)</span></p><p><b>quantity</b>: 0.55</p><h3>SampleSizes</h3><table class="grid"><tr><td style="display: none">-</td><td><b>Description</b></td><td><b>NumberOfStudies</b></td><td><b>NumberOfParticipants</b></td></tr><tr><td style="display: none">*</td><td>21 cohort studies with 133,524 patients after bariatric surgery and 263,478 obese controls</td><td>21</td><td>397002</td></tr></table><blockquote><p><b>attributeEstimate</b></p><p><b>description</b>: 95% confidence interval 0.49 to 0.62</p><p><b>type</b>: Confidence interval <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://terminology.hl7.org/5.5.0/CodeSystem-attribute-estimate-type.html">StatisticAttribute Estimate Type</a>#C53324)</span></p><p><b>level</b>: 0.95</p><p><b>range</b>: 0.49-0.62</p></blockquote><blockquote><p><b>attributeEstimate</b></p><p><b>description</b>: z = 9.41</p><p><b>type</b>: Z-score <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="CodeSystem-179423.html">Evidence Based Medicine on FHIR Implementation Guide Code System</a>#defined-in-text &quot;Defined in text&quot;)</span></p><p><b>quantity</b>: 9.41</p></blockquote><blockquote><p><b>attributeEstimate</b></p><p><b>description</b>: p &lt; 0.00001</p><p><b>type</b>: P-value <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://terminology.hl7.org/5.5.0/CodeSystem-attribute-estimate-type.html">StatisticAttribute Estimate Type</a>#C44185)</span></p><p><b>quantity</b>: &lt;0.00001</p></blockquote><blockquote><p><b>attributeEstimate</b></p><p><b>description</b>: Tau squared = 0.06</p><p><b>type</b>: Tau squared <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://terminology.hl7.org/5.5.0/CodeSystem-attribute-estimate-type.html">StatisticAttribute Estimate Type</a>#0000421)</span></p><p><b>quantity</b>: 0.06</p></blockquote><blockquote><p><b>attributeEstimate</b></p><p><b>description</b>: Chi square for homogeneity 105.14, df 23 (p &lt; 0.00001)</p><p><b>type</b>: Chi square for homogeneity <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="CodeSystem-179423.html">Evidence Based Medicine on FHIR Implementation Guide Code System</a>#defined-in-text &quot;Defined in text&quot;)</span></p><p><b>quantity</b>: 105.14</p><h3>AttributeEstimates</h3><table class="grid"><tr><td style="display: none">-</td><td><b>Description</b></td><td><b>Type</b></td><td><b>Quantity</b></td></tr><tr><td style="display: none">*</td><td>degrees of freedom (df) = 23</td><td>Degrees of Freedom <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="CodeSystem-179423.html">Evidence Based Medicine on FHIR Implementation Guide Code System</a>#defined-in-text &quot;Defined in text&quot;)</span></td><td>23</td></tr><tr><td style="display: none">*</td><td>p &lt; 0.00001</td><td>P-value <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://terminology.hl7.org/5.5.0/CodeSystem-attribute-estimate-type.html">StatisticAttribute Estimate Type</a>#C44185)</span></td><td>&lt;0.00001</td></tr></table></blockquote><blockquote><p><b>attributeEstimate</b></p><p><b>description</b>: I-squared = 78%</p><p><b>type</b>: I-squared <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://terminology.hl7.org/5.5.0/CodeSystem-attribute-estimate-type.html">StatisticAttribute Estimate Type</a>#0000420)</span></p><p><b>quantity</b>: 78 %<span style="background: LightGoldenRodYellow"> (Details: UCUM code % = '%')</span></p></blockquote><blockquote><p><b>modelCharacteristic</b></p><p><b>code</b>: Hazard ratios were log transformed, and the CI was converted to standard error = (upper limit − lower limit)/3.92 for 95% CI. In random effect models (DerSimonian and Laird), we analysed adjusted HR to generate pooled HRs for the association between bariatric surgery for outcome in comparison with controls. The pooled HRs were calculated using inverse-variance weighted averaging and were depicted in forest plots. <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="CodeSystem-179423.html">Evidence Based Medicine on FHIR Implementation Guide Code System</a>#defined-in-text &quot;Defined in text&quot;)</span></p></blockquote><blockquote><p><b>modelCharacteristic</b></p><p><b>code</b>: Meta-analysis <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://hl7.org/fhir/R5/codesystem-statistic-model-code.html">Statistic Model Code</a>#metaAnalysis)</span></p></blockquote><blockquote><p><b>modelCharacteristic</b></p><p><b>code</b>: Random-effects <span style="background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki"> (<a href="http://hl7.org/fhir/R5/codesystem-statistic-model-code.html">Statistic Model Code</a>#effectsRandom)</span></p></blockquote></blockquote></div>
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  <date value="2022-09-19T21:27:50.801Z"/>
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              value="Bariatric surgery and cardiovascular disease: a systematic review and meta-analysis [Journal Article]. Contributors: van Veldhuisen SL, Gorter TM, van Woerden G, de Boer RA, Rienstra M, Hazebroek EJ, van Veldhuisen DJ. In: European heart journal, PMID 35243488. Published March 04, 2022. Available at: https://pubmed.ncbi.nlm.nih.gov/35243488/."/>
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               value="effect estimate for bariatric surgery on all-cause mortality pooled hazard ratio (HR) 0.55 (95% confidence interval 0.49 to 0.62; P &lt; 0.001 vs. controls) in meta-analysis of 21 cohort studies with 133,524 patients after bariatric surgery and 263,478 obese controls"/>
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             value="The present systematic review and meta-analysis suggests that bariatric surgery is associated with reduced all-cause and CV mortality."/>
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                 value="obese, adult (age ≥18 years old) patients *NOTE: note.text is used artificially to support the EBMonFHIR Implementation Guide and the following content would more properly be found in a note.text element:* Studies were considered eligible if they were designed to study outcomes in obese patients who underwent a weight-loss surgical intervention in comparison with an age, sex, and BMI matched control group who did not undergo a weight-loss surgical intervention. We searched for randomized controlled trials, prospective or retrospective longitudinal cohort studies, and case–control studies. For the control group, all non-surgical treatment options for obesity (e.g. intensive lifestyle intervention, standard of care, or no specific therapy) were accepted. Studies were excluded if (i) patients were not matched for age, sex, and BMI; (ii) the presence of one or more outcome parameters of interest (e.g. HF, AF, coronary artery disease) was required for inclusion; or (iii) if study groups were not representative in relation to the general population of patients with obesity (e.g. patients could only be included in the presence of a specific comorbidity, for instance, end-stage renal disease). The third criterium did not apply to Type 2 diabetes, thus studies that only included patients with Type 2 diabetes could be eligible for inclusion."/>
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                 value="comparison groups of bariatric surgery vs. no bariatric surgery *NOTE: note.text is used artificially to support the EBMonFHIR Implementation Guide and the following content would more properly be found in a note.text element:* As the control group (observed reference exposure) was defined differently in each study, the intended reference exposure is described as the absence of the intended exposure (Bariatric Surgery)."/>
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      <text value="Use extension:variableRoleCode instead."/>
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      <reference value="EvidenceVariable/172427"/>
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      <display
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                 value="All-cause mortality *NOTE: note.text is used artificially to support the EBMonFHIR Implementation Guide and the following content would more properly be found in a note.text element:* The observed element can reference an EvidenceVariable Resource that defines the outcome measured through structured characteristics. For example, “Mean difference in HbA1c at 12 months” or “Mean difference in HbA1c at end of study”. The structured characteristics can be references to the Evidence instances for each of the included studies, in which case this is a direct link to the dataset used for analysis. The intended element can reference an EvidenceVariable Resource that expresses the outcome intended for evidence application through structured characteristics. The structured characteristics could be used to express the SR eligibility criteria for study outcomes (as a subset of eligibility criteria for studies)."/>
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      </coding>
      <text value="Use extension:variableRoleCode instead."/>
    </variableRole>
    <observed>
      <display
               value="We searched for randomized controlled trials, prospective or retrospective longitudinal cohort studies, and case–control studies. For the control group, all non-surgical treatment options for obesity (e.g. intensive lifestyle intervention, standard of care, or no specific therapy) were accepted. Studies were excluded if (i) patients were not matched for age, sex, and BMI; (ii) the presence of one or more outcome parameters of interest (e.g. HF, AF, coronary artery disease) was required for inclusion; or (iii) if study groups were not representative in relation to the general population of patients with obesity (e.g. patients could only be included in the presence of a specific comorbidity, for instance, end-stage renal disease). The third criterium did not apply to Type 2 diabetes, thus studies that only included patients with Type 2 diabetes could be eligible for inclusion."/>
    </observed>
    <intended>🔗 
      <reference value="EvidenceVariable/49217"/>
      <type value="EvidenceVariable"/>
      <display value="OutcomeVariable: All-cause mortality"/>
    </intended>
  </variableDefinition>
  <synthesisType>
    <coding>
      <system value="http://terminology.hl7.org/CodeSystem/synthesis-type"/>
      <version value="3.1.0"/>
      <code value="std-MA"/>
      <display value="summary data meta-analysis"/>
    </coding>
  </synthesisType>
  <studyDesign>
    <coding>
      <system value="http://hl7.org/fhir/study-design"/>
      <version value="5.0.0-cibuild"/>
      <code value="SEVCO:01002"/>
      <display value="Observational research"/>
    </coding>
  </studyDesign>
  <studyDesign>
    <coding>
      <system value="http://hl7.org/fhir/study-design"/>
      <version value="5.0.0-cibuild"/>
      <code value="SEVCO:01011"/>
      <display value="Parallel cohort design"/>
    </coding>
  </studyDesign>
  <studyDesign>
    <coding>
      <system value="http://hl7.org/fhir/study-design"/>
      <version value="5.0.0-cibuild"/>
      <code value="SEVCO:01014"/>
      <display value="Matching for comparison"/>
    </coding>
  </studyDesign>
  <statistic>
    <description
                 value="pooled hazard ratio (HR) 0.55 (95% confidence interval 0.49 to 0.62; P &lt; 0.001 vs. controls) in meta-analysis of 21 cohort studies with 133,524 patients after bariatric surgery and 263,478 obese controls"/>
    <note>
      <text
            value="heterogeneity: Tau2 = 0.06; Chi2 = 105.14; df = 23 (P &lt; 0.00001); I2 = 78%"/>
    </note>
    <note>
      <text value="test for overall effect z = 9.41 (p &lt; 0.00001)"/>
    </note>
    <statisticType>
      <coding>
        <system value="http://terminology.hl7.org/CodeSystem/statistic-type"/>
        <code value="C93150"/>
        <display value="Hazard Ratio"/>
        <userSelected value="true"/>
      </coding>
    </statisticType>
    <quantity>
      <value value="0.55"/>
    </quantity>
    <sampleSize>
      <description
                   value="21 cohort studies with 133,524 patients after bariatric surgery and 263,478 obese controls"/>
      <numberOfStudies value="21"/>
      <numberOfParticipants value="397002"/>
    </sampleSize>
    <attributeEstimate>
      <description value="95% confidence interval 0.49 to 0.62"/>
      <type>
        <coding>
          <system
                  value="http://terminology.hl7.org/CodeSystem/attribute-estimate-type"/>
          <code value="C53324"/>
          <display value="Confidence interval"/>
        </coding>
      </type>
      <level value="0.95"/>
      <range>
        <low>
          <value value="0.49"/>
        </low>
        <high>
          <value value="0.62"/>
        </high>
      </range>
    </attributeEstimate>
    <attributeEstimate>
      <description value="z = 9.41"/>
      <type>
        <coding>
          <system value="https://fevir.net/resources/CodeSystem/179423"/>
          <code value="defined-in-text"/>
          <display value="Defined in text"/>
        </coding>
        <text value="Z-score"/>
      </type>
      <quantity>
        <value value="9.41"/>
      </quantity>
    </attributeEstimate>
    <attributeEstimate>
      <description value="p &lt; 0.00001"/>
      <type>
        <coding>
          <system
                  value="http://terminology.hl7.org/CodeSystem/attribute-estimate-type"/>
          <code value="C44185"/>
          <display value="P-value"/>
        </coding>
      </type>
      <quantity>
        <value value="0.00001"/>
        <comparator value="&lt;"/>
      </quantity>
    </attributeEstimate>
    <attributeEstimate>
      <description value="Tau squared = 0.06"/>
      <type>
        <coding>
          <system
                  value="http://terminology.hl7.org/CodeSystem/attribute-estimate-type"/>
          <code value="0000421"/>
          <display value="Tau squared"/>
        </coding>
      </type>
      <quantity>
        <value value="0.06"/>
      </quantity>
    </attributeEstimate>
    <attributeEstimate>
      <description
                   value="Chi square for homogeneity 105.14, df 23 (p &lt; 0.00001)"/>
      <type>
        <coding>
          <system value="https://fevir.net/resources/CodeSystem/179423"/>
          <code value="defined-in-text"/>
          <display value="Defined in text"/>
        </coding>
        <text value="Chi square for homogeneity"/>
      </type>
      <quantity>
        <value value="105.14"/>
      </quantity>
      <attributeEstimate>
        <description value="degrees of freedom (df) = 23"/>
        <type>
          <coding>
            <system value="https://fevir.net/resources/CodeSystem/179423"/>
            <code value="defined-in-text"/>
            <display value="Defined in text"/>
          </coding>
          <text value="Degrees of Freedom"/>
        </type>
        <quantity>
          <value value="23"/>
        </quantity>
      </attributeEstimate>
      <attributeEstimate>
        <description value="p &lt; 0.00001"/>
        <type>
          <coding>
            <system
                    value="http://terminology.hl7.org/CodeSystem/attribute-estimate-type"/>
            <code value="C44185"/>
            <display value="P-value"/>
          </coding>
        </type>
        <quantity>
          <value value="0.00001"/>
          <comparator value="&lt;"/>
        </quantity>
      </attributeEstimate>
    </attributeEstimate>
    <attributeEstimate>
      <description value="I-squared = 78%"/>
      <type>
        <coding>
          <system
                  value="http://terminology.hl7.org/CodeSystem/attribute-estimate-type"/>
          <code value="0000420"/>
          <display value="I-squared"/>
        </coding>
      </type>
      <quantity>
        <value value="78"/>
        <unit value="%"/>
        <system value="http://unitsofmeasure.org"/>
        <code value="%"/>
      </quantity>
    </attributeEstimate>
    <modelCharacteristic>
      <code>
        <coding>
          <system value="https://fevir.net/resources/CodeSystem/179423"/>
          <code value="defined-in-text"/>
          <display value="Defined in text"/>
        </coding>
        <text
              value="Hazard ratios were log transformed, and the CI was converted to standard error = (upper limit − lower limit)/3.92 for 95% CI. In random effect models (DerSimonian and Laird), we analysed adjusted HR to generate pooled HRs for the association between bariatric surgery for outcome in comparison with controls. The pooled HRs were calculated using inverse-variance weighted averaging and were depicted in forest plots."/>
      </code>
    </modelCharacteristic>
    <modelCharacteristic>
      <code>
        <coding>
          <system value="http://hl7.org/fhir/statistic-model-code"/>
          <code value="metaAnalysis"/>
          <display value="Meta-analysis"/>
        </coding>
      </code>
    </modelCharacteristic>
    <modelCharacteristic>
      <code>
        <coding>
          <system value="http://hl7.org/fhir/statistic-model-code"/>
          <code value="effectsRandom"/>
          <display value="Random-effects"/>
        </coding>
      </code>
    </modelCharacteristic>
  </statistic>
</Evidence>