Use of LOINC for interoperability between organisations poses a risk to safety
Authors: Alexis B Carter, Monica E de Baca, Hung S Luu, W Scott Campbell, Michelle N Stram
Journal: The Lancet Digital Health (2020)

Jacob McKnight and colleagues1McKnight J Wilson M Banning P et al.Effective coding is key to the development and use of the WHO Essential Diagnostics List.Lancet Digit Health. 2019; 1: e387-e388Summary Full Text Full Text PDF Scopus (3) Google Scholar extol the positive impact of WHO's Essential Diagnostics List and assert that Logical Observation Identifiers Names and Codes (LOINC) will benefit its implementation.1McKnight J Wilson M Banning P et al.Effective coding is key to the development and use of the WHO Essential Diagnostics List.Lancet Digit Health. 2019; 1: e387-e388Summary Full Text Full Text PDF Scopus (3) Google Scholar The absence of robust interoperability for laboratory test results is problematic, but flaws in LOINC render them unsafe for interoperability between organisations. The original purpose of LOINC was to assign unique, unrelated and non-hierarchical codes to laboratory result names so that tests done at different laboratories could be aggregated, independent of local naming practices. Unlike the hierarchical coding systems SNOMED CT and ICD-10, the flat structure of LOINC precludes data aggregation of related granular concepts under a more general structure. LOINC also do not have a computable infrastructure to enable logical inferences and relationships between parts, terms, and concepts. To achieve data aggregation, LOINC must be mapped with absolute precision and accuracy. Using LOINC to search for tests increases the risk of error and has restricted utility. Appropriate test names and intuitive search keywords are more sensible.2Hickner J Thompson PJ Wilkinson T et al.Primary care physicians' challenges in ordering clinical laboratory tests and interpreting results.J Am Board Fam Med. 2014; 27: 268-274Crossref PubMed Scopus (80) Google Scholar Using the search feature on the LOINC website will disabuse the notion that patients without medical backgrounds could accurately compare tests using LOINC. The continuous updates to LOINC are difficult to maintain. Manufacturer-provided codes have increased duplication and overlap. Non-specific codes and overlapping or unspecified specimen types create confusion. Single results might require multiple codes, and many tests have no code. A coagulation and cardiac markers proficiency testing programme survey showed inaccurate assignment of codes for nearly 20% of tests.3Stram M Seheult J Sinard JH et al.A survey of LOINC code selection practices among participants of the College of American Pathologists' Coagulation (CGL) and Cardiac Markers (CRT) Proficiency Testing Programs.Arch Pathol Lab Med. 2010; 144: 586-596Crossref Scopus (2) Google Scholar As an electronic health record increases its number of interfaced reference laboratories, proportionally greater percentages of results might display inaccurately or misleadingly with little or no means of detection by health-care providers.4Lin MC Vreeman DJ McDonald CJ Huff SM A characterisation of local LOINC mapping for laboratory tests in three large institutions.Methods Inf Med. 2011; 50: 105-114Crossref PubMed Scopus (29) Google Scholar, 5Bhargava A Kim T Quine DB Hauser RG A 20–year evaluation of LOINC in the United States' largest integrated health system.Arch Pathol Lab Med. 2020; 144: 478-484Crossref PubMed Scopus (5) Google Scholar The human resources required to ensure safe use for interoperability preclude many systems from using LOINC, even between multiple sites of a single organisation where local control can mitigate some of the flaws. Although US laboratories are required to use LOINC to encode laboratory result names, they are not required to use them for interoperability. Coding orders and observations are neither mandated nor done by most organisations. We believe that use of LOINC is not universal, is difficult to implement, and is unsafe for inter-organisational interoperability. Currently, there are no interoperability alternatives to LOINC other than current methods of manual mapping to ensure accurate charting. Complexity in medicine and pathology increase daily with new discoveries and laboratory tests. Until a viable alternative exists, safe interoperability will continue to require manual mapping by those with expertise in laboratory medicine. We declare no competing interests. Effective coding is key to the development and use of the WHO Essential Diagnostics ListThe WHO new Essential Diagnostics List (EDL) aims to provide a structure for identifying, promoting, and increasing the supply and availability of the most effective and important in-vitro diagnostics (a full list of the included diagnostics is available in the appendix). The first edition of the EDL was published in November, 2018, but many revisions are expected given both its novelty and its importance in setting goals for health policy makers globally. It has no international antecedents, but the intention is to build on the success of WHO's well established Essential Medicines List. Full-Text PDF Open AccessUse of LOINC for interoperability between organisations poses a risk to safety – Authors' replyWe thank Alexis Carter and colleagues for the opportunity to revisit this important topic. The use of diagnostic coding systems is a contentious area and represents a further reason why the WHO Essential Diagnostics List (EDL) team should engage the community of specialists in this field before publication of the next edition. Full-Text PDF Open Access