Page 40 - PATIENT REGISTRY DATA FOR RESEARCH: A Basic Practical Guide

to the sixth and seventh digits' number) by referring to the 12-digit number on the person's

identification card.

Although it is always possible to have erred by determining someone's ethnicity by

basing on his/her name alone, the above-mentioned method is considered a more objective

way to determine a person's ethnicity, which makes it more relevant for the Malaysian

patients. Apart from this, it is usually possible to decipher a person's gender based on his/her

name alone. However, the researcher must also have to accept the fact it is also possible for a

deviation from the truth to occur if he/she is imputing a 'missing' gender by basing on the

person's name alone. Thus, it is necessary to declare such limitations in the study report or

manuscript in order to make them transparent to all the readers.

On the other hand, imputation is a technique which replaces the missing data with a

probable value which has been estimated by mathematical computations. There are many

imputation techniques which can be applied in patient registry databases, such as the single

imputation methods (including mean imputation, median imputation, conditional mean

imputation) and the multiple imputation methods (including hot decking method and multiple

imputation by chained equations). However, a full discussion of all these imputation

techniques is beyond the scope of this paper, and so the reader is advised to look up other

relevant sources for further information about these techniques.

The decision to apply imputation techniques to rectify the error caused by missing

data also depends on the objective of the study. In some technical reports, it is necessary to

report missing data in order to evaluate the competency of the registry for collecting

information. Hence, imputation will not be necessary in such instances. When imputation is

deemed necessary in other circumstances, then the researcher shall have to select an

appropriate imputation technique and to provide a valid justification for it.