The practical use of a Query by Field can be seen in the following example.

A transfusion service manager is approached by a technologist with a sample that has an illegible label and that was collected in L&D during the previous night. The manager remembers seeing other errors like this. She performs a Query by Field in MERS-TM, looking for the following data element values:

• errors occurring in sample collection (SC)
• event occurring between midnight and 8 a.m.
• event occurring in L&D department

The results showed that there were four other events in the prior three months that shared these characteristics. She presents this data to the head nurse in L&D for discussion with the nursing staff.