Evaluation of multiple imputation to address intended and unintended missing data in case-cohort studies with a binary endpoint

TL;DR

This study compares multiple imputation, inverse probability weighting, and their combination for handling missing data in case-cohort studies with binary outcomes, finding that combined MI and IPW approaches reduce bias especially in small samples.

Contribution

It provides the first comprehensive simulation comparison of MI, IPW, and their combination for binary outcomes in case-cohort studies with both intended and unintended missing data.

Findings

Combined MI and IPW approach is approximately unbiased in large samples.

MI-only or IPW-only methods exhibit larger biases in small samples.

The study supports using MI for handling missing data in binary case-cohort studies.

Abstract

Case-cohort studies are conducted within cohort studies, wherein collection of exposure data is limited to a subset of the cohort, leading to a large proportion of missing data by design. Standard analysis uses inverse probability weighting (IPW) to address this intended missing data, but little research has been conducted into how best to perform analysis when there is also unintended missingness. Multiple imputation (MI) has become a default standard for handling unintended missingness, but when used in combination with IPW, the imputation model needs to take account of the weighting to ensure compatibility with the analysis model. Alternatively, MI could be used to handle both the intended and unintended missingness. While the performance of a solely MI approach has been investigated in the context of a case-cohort study with a time-to-event outcome, it is unclear how this approach performs with binary outcomes. We conducted a simulation study to assess and compare the performance of approaches using only MI, only IPW, and a combination of MI and IPW, for handling intended and unintended missingness in this setting. We also applied the approaches to a case study. Our results show that the combined approach is approximately unbiased for estimation of the exposure effect when the sample size is large, and was the least biased with small sample sizes, while MI-only or IPW-only exhibited larger biases in both sample size settings. These findings suggest that MI is the preferred approach to handle intended and unintended missing data in case-cohort studies with binary outcomes.