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Open Access 01-12-2020 | Research article

Summarizing the extent of visit irregularity in longitudinal data

Authors: Armend Lokku, Lily S. Lim, Catherine S. Birken, Eleanor M. Pullenayegum, on behalf of the TARGet Kids! Collaboration

Published in: BMC Medical Research Methodology | Issue 1/2020

Abstract

Background

Observational longitudinal data often feature irregular, informative visit times. We propose descriptive measures to quantify the extent of irregularity to select an appropriate analytic outcome approach.

Methods

We divided the study period into bins and calculated the mean proportions of individuals with 0, 1, and > 1 visits per bin. Perfect repeated measures features everyone with 1 visit per bin. Missingness leads to individuals with 0 visits per bin while irregularity leads to individuals with > 1 visit per bin. We applied these methods to: 1) the TARGet Kids! study, which invites participation at ages 2, 4, 6, 9, 12, 15, 18, 24 months, and 2) the childhood-onset Systemic Lupus Erythematosus (cSLE) study which recommended at least 1 visit every 6 months.

Results

The mean proportions of 0 and > 1 visits per bin were above 0.67 and below 0.03 respectively in the TARGet Kids! study, suggesting repeated measures with missingness. For the cSLE study, bin widths of 6 months yielded mean proportions of 1 and > 1 visits per bin of 0.39, suggesting irregular visits.

Conclusions

Our methods describe the extent of irregularity and help distinguish between protocol-driven visits and irregular visits. This is an important step in choosing an analytic strategy for the outcome.

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Title: Summarizing the extent of visit irregularity in longitudinal data
Authors: Armend Lokku
Lily S. Lim
Catherine S. Birken
Eleanor M. Pullenayegum
on behalf of the TARGet Kids! Collaboration
Publication date: 01-12-2020
Publisher: BioMed Central
Published in: BMC Medical Research Methodology / Issue 1/2020
Electronic ISSN: 1471-2288
DOI: https://doi.org/10.1186/s12874-020-01023-w

Keynote webinar | Spotlight on medication adherence

Springer Medicine

Summarizing the extent of visit irregularity in longitudinal data

Abstract

Background

Methods

Results

Conclusions

Keynote webinar | Spotlight on medication adherence

Springer Medicine

Abstract

Background

Methods

Results

Conclusions

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