Table 1. Types of Missing Values.

Types of missing values	Description	Possible causes
Missing completely at random	Missing data occur completely at random without being influenced by other data.	Consent withdrawal, omission of major exams, death, discontinued follow-up and serious adverse reactions.
Missing at random	Missing data occur at a specific time point in conjunction with participant dissatisfaction with study outcomes and ongoing participation	Refusal to continue measurements.
Not missing at random	Missing data occur when a patient who is not satisfied with study outcomes performs the required measurements on his own, before the scheduled measurement.	If a patient finds the results of self-measurement dissatisfactory in addition to dissatisfaction related to the study, the patient may refuse further measurements.