Risk-set exposure and covariate ascertainment

Anchor measurements to index times

Anchor all members of a matched set to the case event time. Store person and set identifiers separately and preserve the date of specimens or measurements used to reconstruct prior exposure.

Flow diagram

Risk-set exposure and covariate ascertainmentF1.S1Anchor measurements to index timeF1.S2Define exposure windowsF1.S3Measure covariates consistentlyF1.S4Resolve repeated-person recordsF1.S5Version ascertainment rulesF1.N1Index-time measurement dictionaryVariableWindowSourceLagMissingnessExposureConfoundersEffectmodifiersF1.N2Assumptions and rationaleF1.N3Method and protocol evidenceF1.S0 Start flowRisk-set exposure and covariateascertainmentF1.S999 End flowEnd flow

Steps

Anchor measurements to index time

Use the case event time for each matched set.

Define exposure windows

Specify lookback, lags, recent exposure and unavailable history.

Measure covariates consistently

Use equivalent opportunities for cases and sampled controls.

Resolve repeated-person records

Retain episode and set identifiers when a person appears more than once.

Version ascertainment rules

Record measurement sources, coding and missingness handling.

Risk-set exposure and covariate ascertainment

End flow

Tables and supporting information

Index-time measurement dictionary

Index-time measurement dictionaryVariableWindowSourceLagMissingnessExposureConfoundersEffectmodifiers

Do not use information recorded after the matched index time to define baseline exposure.

Assumptions and rationale

Unequal ascertainment or future-information leakage can compromise the sampled comparison.

Method and protocol evidence

Attach the protocol, methodological sources and versioned software specification supporting these decisions. Record citations and provenance; do not enter participant identifiers.

Sources