The Newcastle-Ottawa Scale (NOS) for Assessing the Quality of Nonrandomized Studies in Meta-AnalysisG. Wells, B. Shea, D. OConnell, J. Robertson, J. Peterson, V. Welch, M. Losos, P. Tugwell

Development

Applications

Current Developments

Development: Item SelectionNewcastle quality assessment formOttawa comprehensive listPanel reviewCritical review by experts

Development: Grouping ItemsCohort studiesSelection of cohortsComparability of cohortsAssessment of outcome

Case-Control studiesSelection of case and controlsComparability of cases and controlsAscertainment of exposure

Development: Identifying ItemsIdentify high quality choices with a starA maximum of one star for each h item within the Selection and Exposure/Outcome categories; maximum of two stars for Comparability

Newcastle-Ottawa Quality Assessment Scale: Case-Control StudiesSelection (4)

Comparability (1)

Exposure (3)

A study can be awarded a maximum of one star for each numbered item within the Selection and Exposure categories. A maximum of two stars can be given for Comparability

Selection1. Is the case definition adequate? a) yes, with independent validation b) yes, eg record linkage or based on self reports c) no description

2. Representativeness of the cases a) consecutive or obviously representative series of cases b) potential for selection biases or not stated

3. Selection of Controls a) community controls b) hospital controls c) no description

4. Definition of Controls a) no history of disease (endpoint) b) no description of source >1 person/record/time/process to extract information, or reference to primary record source such as x-rays or medical/hospital recordse.g. ICD codes in database or self-report with no reference to primary record or no description

Comparability1. Comparability of cases and controls on the basis of the design or analysis a) study controls for ___________ (select the most important factor) b) study controls for any additional factor (This criteria could be modified to indicate specific control for a second important factor.)

Exposure1. Ascertainment of exposure a) secure record (eg surgical records) b) structured interview where blind to case/control status c) interview not blinded to case/control status d) written self report or medical record only e) no description

2. Same method of ascertainment for cases and controls a) yes b) no

3. Non-Response Rate a) same rate for both groups b) non respondents described c) rate different and no designation

Newcastle-Ottawa Quality Assessment Scale: Cohort StudiesSelection (4)

Comparability (1)

Outcome (3)

A study can be awarded a maximum of one star for each numbered item within the Selection and outcome categories. A maximum of two stars can be given for Comparability

Selection1. Representativeness of the exposed cohort a) truly representative of the average ___________ (describe) in the community b) somewhat representative of the average ___________ in the community c) selected group of users eg nurses, volunteers d) no description of the derivation of the cohort

2. Selection of the non exposed cohort a) drawn from the same community as the exposed cohort b) drawn from a different source c) no description of the derivation of the non exposed cohort

3. Ascertainment of exposure to implants a) secure record (eg surgical records) b) structured interview c) written self report d) no description

4. Demonstration that outcome of interest was not present at start of study a) yes b) no In the case of mortality studies, outcome of interest is still the presence of a disease/ incident, rather than death; that is a statement of no history of disease or incident earns a star

Comparability1. Comparability of cohorts on the basis of the design or analysis a) study controls for ___________ (select the most important factor) b) study controls for any additional factor (This criteria could be modified to indicate specific control for a second important factor.)

Outcome1. Assessment of outcome a) independent blind assessment b) record linkage c) self report d) no description

2. Was follow up long enough for outcomes to occur a) yes (select an adequate follow up period for outcome of interest) b) no

3. Adequacy of follow up of cohorts a) complete follow up - all subjects accounted for b) subjects lost to follow up unlikely to introduce bias - small number lost - > ___ % (select an adequate %) follow up, or description of those lost) c) follow up rate < ___% (select an adequate %) and no description of those lost d) no statement

Applications:Assess quality of nonrandomized studiesIncorporate assessments in interpretation of meta-analytic resultsDesign, content and ease of use

Long Term Hormone Replacement Therapy and Coronary Heart Disease Events

Steps of a Cochrane Systematic ReviewClearly formulated questionComprehensive data searchUnbiased selection and abstraction processCritical appraisal of dataSynthesis of dataPerform sensitivity and subgroup analyses if appropriate and possiblePrepare a structured report

ObjectiveIs there a relationship between hormone replacement therapy and the incidence of coronary heart disease in postmenopausal women

Inclusion CriteriaTypes of studiescase-control, cohort or cross-sectional studiesPopulationpostmenopausal womenInterventionwomen exposed to hormone replacement therapy (estrogen or estrogen + progesterone)ever, current, pastOutcomescoronary heart disease (events)fatal, non-fatal, both

Steps of a Cochrane Systematic ReviewClearly formulated questionComprehensive data searchUnbiased selection and abstraction processCritical appraisal of dataSynthesis of dataPerform sensitivity and subgroup analyses if appropriate and possiblePrepare a structured report

Search StrategyElectronic Search of:MEDLINE (1966 to May 2000)Current Contents (to May 2000)

Other Data Sources:review of references cited in retrieved articles

Steps of a Cochrane Systematic ReviewClearly formulated questionComprehensive data searchUnbiased selection and abstraction processCritical appraisal of dataSynthesis of dataPerform sensitivity and subgroup analyses if appropriate and possiblePrepare a structured report

Data Extraction2 independent reviewers selected trials2 independent reviewers extracted data using pre-determined formsstudy designpopulation characteristicsexposure to implantsoutcomes measuresresultsdifferences resolved by consensus

Results16 case-control or cross-sectional14 cohort

Quantification of EffectsExposure (ever, current, past)Outcome (fatal, non-fatal, both) Effect estimates (EE)Relative Risk (RR) Odds Ratio (OR)Adjusted effect estimatesEffects vs population, follow-up periods, etc. (homogeneity)

Steps of a Cochrane Systematic ReviewClearly formulated questionComprehensive data searchUnbiased selection and abstraction processCritical appraisal of dataSynthesis of dataPerform sensitivity and subgroup analyses if appropriate and possiblePrepare a structured report

Avila / 90Cauley / 97Grodstein / 96Henderson / 91Lafferty / 94Wilson / 85Wolf / 96Lauritzen / 83Ettinger / 96Petitti / 87Sourander / 98Bush / 87Criqui / 98Folsom / 95Cohort Star TemplateSelection Comparability Outcome

Adam / 81Beard / 89Croft / 89Grodstein / 97Heckbert / 97LaVecchia / 87Mann / 94Pfeffer / 78Rosenberg / 76Rosenberg / 80Rosenberg / 93Ross / 81Sidney / 97Szklo / 84Talbott / 77Thompson / 89Case-Control Star TemplateSelection Comparability Exposure

Adjusted Effect Estimates for Coronary Heart Disease (All Events) (HRT: Estrogen Current Use)Case-Control Studies Selection Comparability Exposure

Adjusted Effect Estimates for Coronary Heart Disease (All Events) (HRT: Estrogen Past Use)Case-Control StudiesSelection Comparability Exposure

Adjusted Effect Estimates for Coronary Heart Disease (All Events) (HRT: Estrogen Ever Use)Case-Control StudiesSelection Comparability Exposure

Adjusted Effect Estimates for Coronary Heart Disease (All Events) (HRT: Estrogen + Progestin Ever Use)Case-Control StudiesSelection Comparability Exposure

Adjusted Effect Estimates for Coronary Heart Disease (All Events) (HRT: Estrogen Current Use)Cohort StudiesSelection Comparability Outcome

Adjusted Effect Estimates for Coronary Heart Disease (All Events) (HRT: Estrogen Ever Use)Cohort StudiesSelection Comparability Outcome

Current Development: Validity Face/content validityCriterion validitycompare to more comprehensive scalescompare to expert judgementConstruct validityexternal criteriaconvergent validitydivergent validityinternal structurefactorial validity

Current Development: Reliability Inter-rater reliabilityIntra-rater reliability

Future Development: Scoring Identify threshold score distinguishing between good and poor quality studies

The Newcastle-Ottawa Scale (NOS) for Assessing the Quality of Nonrandomized Studies in Meta-Analysiswww.lri.ca

NOS Quality Assessment Scales:Case-control studiesCohort studiesManual for NOS Scales