Criteria to assess quality of Criteria to assess quality of observational studies evaluating the observational studies evaluating the

incidence, prevalence, and risk incidence, prevalence, and risk factors of chronic diseasesfactors of chronic diseases

Minnesota EPCClinical Epidemiology Methods Centre, Ottawa Health Research Institute, Ottawa

Tufts University Medical Center, BostonRTI International – University of North Carolina, Chapel Hill

Blue Cross and Blue Shield Association, ChicagoCenters for Disease Control and Prevention, Atlanta

Southern California EPC; RAND Corporation, Santa MonicaGerman Institute for Quality and Efficiency in Health Care, Köln, Germany

Johns Hopkins University, Baltimore

Analytical tasks

III. Collaboration with participating experts

I. Systematic literature review

II. Development of two checklists

IV. Finalizing checklists

Therapeutic vs. non therapeutic studiesPICOTS Non therapeutic studies Non randomized studies

Population General population Patients, health care recipients

Exposure (interventions, independent variables)

Risk factors that are independent of health care (allocation irrelevant)

Treatments allocation by investigators or health care professionals

Comparators Levels of risk Another trtm, usual care, standard care, previous trtm

Outcomes Incidence/prevalence of chronic conditions

Morbidity, mortality, quality of life, adverse events after treatments

Time Length of exposure Length of trtm, followup off the trtm

Settings General population Health care settings

Comparability (selection bias)

Not relevant Flaw

Intention-to treat Not relevant Flaw

Systematic literature review

• Systematic reviews and meta-analyses of observational nontherapeutic studies published in English in core clinical journals (145)

• Published tools (scales or checklists) for quality assessment of observational studies (96)

• Annotated bibliography of the methodological literature to identify biases and strategies to reduce bias in observational studies

Development of Checklists• Separate evaluation of external and internal

validity• Exhaustive range of criteria• Discriminating reporting and methodological

quality• Predefined major and minor flaws • Study and hypotheses level analyses• Automated reports• Templates for the protocols of quality

evaluations with predefined research specific quality standards

• Manual, help files, instructions

Collaboration with participating experts

• Criteria evaluation: face and content validity

• Pilot reliability testing (10 randomly selected articles): overall, by topic, by article, by domains of external and internal validity, and by quality component

• Discriminant validity: testing hypotheses of detected differences in quality and reporting vs. methodological quality

Finalizing checklists

• Checklist for studies of incidence or prevalence of chronic diseases (MORE)

• Checklist for studies of risk factors of chronic diseases (MEVORECH)

• Synthesis of evidence from the studies with major flaws:

• Level A exclusion from synthesis • Level B full review and quality abstraction • Level C separate limited synthesis if major flaws detected

Quality criteriaIncidence or prevalence studies

Aim of study Study designExternal Validity1. Sampling of the subjects by the

investigators2. Assessment of sampling bias 3. Estimation of sampling bias4. Exclusion rate from the analysis 5. Sampling bias is addressed in the analysis6. Subject flow Internal Validity1. Source to measure outcomes 2. Definition of outcomes3. Measurements of outcomes4. Outcomes in race, ethnic, age, or gender

subpopulations 5. Reporting of outcomes

Risk factors studiesAim of studyObjectivesStudy design External Validity1. Sampling of the subjects by the investigators2. Assessment of sampling bias 3. Estimation of sampling bias4. Exclusion rate from the analysis 5. Sampling bias is addressed in the analysis 6. Subject flow

Internal Validity1.Source to measure outcomes2. Definition of outcomes3. Measurements of outcomes4. Definition of the exposure 5.Measurements of the exposure 6. Confounding factors7. Loss of followup 8. Masking of exposure status9. Statistical analysis10. Appropriateness of statistical models11. Reporting of tested hypothesis12. Precision of the estimates13. Sample size justification

Major flawsExternal validity

Sampling in clinics forincidence in the generalpopulation;

Sampling of controls from differentpopulation as cases;

Response rate <40%;

Exclusion of >10% of eligible subjectsfrom the analyses

Reasons to exclude from the analysesdiffer for exposed and not exposed

Internal validitySeverity of the outcome can berelevant but not assessed in thestudy;

Non valid methods were obtained tomeasure the outcomes, exposure, orconfounding factors;

Different methods to measureexposure (risk factors, independentvariable) in cases and controls;

No strategies to reduce bias

Minor Flaws• External validity• Random sampling

restricted to geographic area

• Convenient sampling• The authors did not

assess sampling bias • Sampling bias was not

addressed in the analysis• Sampling of controls from

health care related sources

• Internal validity• Outcomes proxy reported• Obtained from medical

records (data mining) or administrative database

• Inter-methods validation • Subjective judgment of

reliability• Intensity/dose of exposure

can be relevant but not assessed in the study

Example of the reportArticle: _________________

Evaluator: _______________

External ValidityNot Reported

Addressing sampling bias Not reported

Sampling: General population based Not reported

Major flaw

Exclusion rate from the analysis >10%

Internal ValidityMajor flaw

Definition of incidence/prevalence: Severity Can be relevant but not assessed in the study

Minor

Definition of incidence/prevalence: Frequency of symptoms

Can be relevant but not assessed in the study

ConclusionsConclusions

• We propose two checklists for transparent and standardized quality assessment in systematic reviews and evidence-based reports

• Reasonable validity• Poor random overall and good

component reliability in a pilot testing of the articles from different topics

Future Research with Quality Assessment Using Proposed Checklists

• Protocols of systematic reviews of nontherapeutic observational studies with justified definitions of research specific quality standards and preplanned reliability testing

• Synthesis of evidence incorporating quality assessment (sensitivity of the results to quality)

• The evaluation of the level of evidence from several observational nontherapeutic studies

• Quality assessment of primary studies should improve quality of systematic reviews and evidence-based reports