Background: Gastrointestinal illnesses and respiratory-related illnesses are common among
young children in Malaysia, especially those who are attending day care. During administration of
probiotic, the occurences of gastrointestinal and respiratory-related illnesses can be reduced. These
were observed by evaluation through a single questionnaire. However, currently no single tool exists
to simultaneously evaluate the domains of gastrointestinal and respiratory-related illnesses among
these young children. The current study aimed to develop a source questionnaire in English, translate
and validate into the Malay. Methods: Relevant domains of gastrointestinal and respiratory-related
illnesses were identified to generate items and formed a screening tool through literature reviews,
focus groups and opinions of experts. Results: The developed Basic Demographic and Lifestyle
Questionnaire (BDLQ) and Monthly Healthy Questionnaires (MHQ) showed item-level content
validity index (I-CVI) of 0.99 and 0.97, respectively, while the translated Malay versions showed I-CVI
of 1.00 and 0.99, respectively. Item-level face validity index (I-FVI) of 1.00 for both questionnaires
were obtained from 30 respondents showing that the items were clear and comprehensible.
Conclusion: This study showed good level of I-CVI and I-FVI in both developed questionnaires and
their Malay translated versions. These tools in English and Malay were valid and thus reliable to be
used for assessing gastrointestinal and respiratory-related illnesses in young children.