How to mask specific elements in HL7?

Question

Currently I am learning how to work with HL7 and how to parse it in python. Now I was wondering what happens if a value in a HL7 segment contains a pipe sign, eg '|'. How is this sign handled? If there is no masking, it would lead to a crash of the HL7 parser. Is there a masking possibility?

Answer 1

\\F\\

You should read the relevant sections of chapter 2 of the version 2 standard about how escaping works in version 2.

Answer 2

The HL7 structure has defined escape sequences for the separators like | . When you look at a HL7 message, the used five delimiters are right after the MSH:

MSH|^~\&

• | is the Field separator F
• ^ the component separator S
• ~ is the repetition separator (for the second level elements) R
• \\ is the escape character E
• & is the sub-component separator T

So to escape one of the special characters like | , you have to take the escape character and then add the defined letter (F,S, etc.)

So in above case, to escape the | you would have to put \\F\\ . Or escaping the escape character is \\E\\ .

If you like you can also change the delimiters after the MSH completely, but I don't recommend that.