LOINC is a standard that facilitates the exchange and pooling of laboratory tests for clinical care, outcomes management, and research. LOINC was established as universal identifiers for laboratory tests and other clinical observations. The laboratory portion of the LOINC database includes categories of chemistry, hematology, serology, microbiology (including parasitology and virology), and toxicology, as well as categories for drugs and the cell counts. Today, the LOINC standard is maintained by the Regenstrief Institute, Inc.
Although LOINC has been in use for the past 15 to 20 years, it is just now being accepted and used by labs and clinicians for cross‐walking information. All three labs that were involved in this study reported that they have capabilities to code and map LOINC and to send codes along with the results as part of the HL7 message. Large national laboratories indicate that, in general, they have mapped the vast majority of the codes to LOINC. In the context of information exchange, the issue of mapping laboratory codes from multiple sources to LOINC can be quite challenging because of the large number (2,000 to 5,000) of distinct test observations per laboratory.32
A recent study by the Regenstrief Institute demonstrated that approximately 800 laboratory codes could account for 99 percent of the test results stored in the clinical databases of their collaborating institutions.33 Consequently, by mapping a small subset of codes, a large fraction of patients would have all their laboratory test results mapped. However, EHR vendors and providers indicate that they rarely receive LOINC codes from clinical laboratories. We found that while the major labs support LOINC, a number of the smaller labs continue to use their own local codes and do not have any mapping to LOINC. In addition, even those labs that have made an effort to map tests to LOINC do not always transmit LOINC codes in results messages. Consequently, depending on the specific market, the labs themselves are not able to send LOINC codes in the results message or do not do so, even if they have the capability.
The labs we spoke with reported concerns that the EHR vendor software may not aggregate and interpret the LOINC mappings correctly, potentially resulting in errors or undefined values when the EHR system receives the information. Therefore, the major labs try to ensure that vendors who ask for LOINC codes know what it means and how to handle the LOINC mapping. Although there are a few examples of LOINC use by organizations such as the Veterans Administration, the Department of Defense, and Kaiser Permanente3435 providers included in the study noted that LOINC is not supported widely in practice, and CCHIT testing of EHRs is the only national driving force for its usage. LOINC codes are very granular and distinguish what type of testing method is used by the lab. For example, there are different LOINC codes for a white blood count that is done manually rather than automatically. While the relevance of the testing methods varies depending on the clinical context, the testing methods do not always materially impact the interpretation of the results by the provider. Thus, depending on the specific example, LOINC codes may also require the implementation of additional logic in the different clinical systems processing this information.
In some cases, the EHR vendors indicated that they have the capacity to map local codes to LOINC but given that the average provider receives results from at least two labs, this would still be a time‐consuming and costly process. EHR vendors also noted that their preference was to consolidate some of the LOINC codes in order to make the implementation more feasible. Today, programmers cannot single‐handedly complete the mapping because it requires extensive clinical knowledge that interface developers may not have. In addition, having a more abstracted version of LOINC would improve the usability and utility of the information being presented to providers.
Given the cost and other challenges with LOINC mapping experienced by labs and EHR vendors, most labs transmit local codes in lieu of standardized LOINC codes. While this approach allows the transmission of lab information to support patient care, it does not support true semantic interoperability between the laboratory information system and the EHR. Consequently, this may limit the ability for lab‐provider exchanges or HITSP standards to be leveraged for regional or nationwide HIE efforts.