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User guide
LOINC Users’ Guide Section 12 C
August 2023
This document is the third subsection of section 12 of the Users’ Guide for LOINC. LOINC is an international standard for identifying health measurements, observations and documents such as laboratory and clinical test results.

Section 12 of the Users’ Guide provides information to help users of LOINC make the best use of the standard. The LOINC code is a numeric code with a Mod 10 check digit. Section 12 C presents the 8-step algorithm for calculating a Mod 10 check digit. It also lists the 14 terms known to have invalid check digits and contains a link on how to calculate check digits for atypical identifiers.

Main sections:

• Algorithm for calculating a Mod 10 check digit

• Terms with invalid check digits

• Calculating the check digit for LOINC Parts, Answers, and other identifiers with characters
Access LOINC Users’ Guide: 12 C – Calculating Mod 10 Check Digits v2023

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