I checked all the loinc numbers in the map_to file. There 2810 records. If I check the all the values in the first column LOINC against the LOINC table I get a match of 2355. If I match the second column MAP_to against the LOINC table I get 2377 matches. I expect a full match on the second colum. Is there someone who can explain why there is not a full match or what is the use of this file?