Advised missing data method

Longitudinal analysis > Missings in predictor/covariate > MNAR > <50% missing data > <75% item missings

The missing data method should be applied to the the item scores in order to use the available item information. In this situation multiple imputation of the item scores can be performed and was shown to work well even in this MNAR missing data mechanism (Eekhout et al., 2014). However, the percentage of subjects with missing values cannot be too large.