Pharmaceutical companies conduct longitudinalstudies on human subjects that often span several months. It is unrealistic to expect patients to KEEP every scheduled visit over such a long period of time.Despite every effort, patient data are not collected for some time points.

Eventually, these become missing VALUES in a SAS data set later. For reporting purposes,the most recent previously available VALUE is substituted for each missing visit. This is called the Last Observation Carried Forward (LOCF).LOCF doesn’t mean last SAS dataset observation carried forward.

It means last non-missing value carried forward. It is the values of individual measures that are the “observations” in this case. And if you have multiple variables containing these values then they will be carried forward INDEPENDENTLY.

Pharmaceutical companies conduct longitudinalstudies on human subjects that often span several months. It is unrealistic to expect patients to keep every scheduled visit over such a long period of time.Despite every effort, patient data are not collected for some time points.

Eventually, these become missing values in a SAS data set later. For reporting purposes,the most recent previously available value is substituted for each missing visit. This is called the Last Observation Carried Forward (LOCF).LOCF doesn’t mean last SAS dataset observation carried forward.

It means last non-missing value carried forward. It is the values of individual measures that are the “observations” in this case. And if you have multiple variables containing these values then they will be carried forward independently.