Simple imputation methods were inadequate for missing not at random (MNAR) quality of life data

Shona Fielding, Peter M Fayers, Alison McDonald, Gladys McPherson, Marion K Campbell, RECORD Study Group

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)
7 Downloads (Pure)


QoL data were routinely collected in a randomised controlled trial (RCT), which employed a reminder system, retrieving about 50% of data originally missing. The objective was to use this unique feature to evaluate possible missingness mechanisms and to assess the accuracy of simple imputation methods.

Those patients responding after reminder were regarded as providing missing responses. A hypothesis test and a logistic regression approach were used to evaluate the missingness mechanism. Simple imputation procedures were carried out on these missing scores and the results compared to the actual observed scores.

The hypothesis test and logistic regression approaches suggested the reminder data were missing not at random (MNAR). Reminder-response data showed that simple imputation procedures utilising information collected close to the point of imputation (last value carried forward, next value carried backward and last-and-next), were the best methods in this setting. However, although these methods were the best of the simple imputation procedures considered, they were not sufficiently accurate to be confident of obtaining unbiased results under imputation.

The use of the reminder data enabled the conclusion of possible MNAR data. Evaluating this mechanism was important in determining if imputation was useful. Simple imputation was shown to be inadequate if MNAR are likely and alternative strategies should be considered.
Original languageEnglish
Article number57
Number of pages9
JournalHealth and Quality of Life Outcomes
Publication statusPublished - 4 Aug 2008

Bibliographical note

We thank the patients who took part in the RECORD study, without whose help this study would not have been possible. The MRC funded the central organisation of RECORD, and Shire Pharmaceuticals Group plc funded the drugs, which were manufactured by Nycomed Ltd. The Health Services Research Unit is funded by the Chief Scientist Office of the Scottish Government Health Directorate. Shona Fielding is also currently funded by the Chief Scientist Office on a Research Training Fellowship (CZF/1/31). The views expressed are, however, not necessarily those of
the funding body.


Dive into the research topics of 'Simple imputation methods were inadequate for missing not at random (MNAR) quality of life data'. Together they form a unique fingerprint.

Cite this