Best Practices for Interoperable Data Exchange Using LOINC

1. Best Practices for Interoperable Data Exchange Using LOINC Ming-Chin (Mark) Lin, MD Stanley M. Huff, MD

2. Introduction • Two primary use cases • Sharing data between and among different institutions for patient care • Aggregating data between and among different institutions for clinical research, quality improvement, public health surveillance, etc. (secondary use) • Use LOINC codes as the linguafranca for the data sharing

3. Introduction (continued) • Mark’s work comparing LOINC usage across ARUP, Regenstrief, and Intermountain • What is truth? • If local codes from different sites are mapped to the same LOINC code, how do we know they are really the same test? • If local codes from different sites are mapped to different LOINC codes, how do we know they are really different tests? • Extensional definitions • Comparison of names (substance, timing, property, specimen), units of measure, mean value, standard deviation, coded values, co-occurring tests, etc. • Results: We found about a 4% error rate in mapping • And that is us! What is it like for “regular” facilities?

4. Introduction (continued) • Analyzing the errors lead to additional questions • Can we classify the errors? • What is the ultimate goal of mapping? • Can we define “best practices” for mapping so that everyone doing mapping can achieve greater accuracy?

5. Principles/Goals in Choosing Best Practices • Optimize for patient safety, interoperability, and secondary use of data • Anticipate change - Make the process as easy as possible when new codes are created, technology changes, or when errors are corrected • Make the practices understandable and reproducible • Have the least possible impact on LOINC staff

6. Approach • State best practices to encourage movement to better processes • We expect this to take time • Don’t try to mandate anything (we don’t have any authority to do that) • Not following best practices is not considered “non compliance” to standards • We may need to change some LOINC content to better support best practices

7. Proposed Process • Create specific best practice guidelines for difficult situations and common errors • Consider a few questions each meeting • As agreements are made, add the best practices as a section in the LOINC manual • Example issues (please contribute your issues) • Specificity of analytes • Best approach for sending method specific data • Best practice for value of quantities and interpretations • How to deal with pre and post coordinated specimen type • How to deal with pre and post coordinated challenge conditions • Use of Acnc and Titr • Etc.

8. Proposal #1 Request a new code when analyte/component details don’t match LOINC exactly

9. Examples • A new local test is for Avian pox virus Ab.IGG • Not a match for Avian pox virus Ab • A new local test is for Avian paramyxovirus 10 Ab • Not a match for Avian paramyxovirusAb • A new local test for 11-Deoxycortisol.free SCnc • Not a match for 11-Deoxycortisol SCnc • Many, many examples where there is a parent-child relationship between items. These are never a match. Always request a new code.

10. Proposal #2 Always send method information as an independent element in the OBX segment.

11. “Fit for Purpose” or “Good Enough” mapping versus “Best Practice” • Example: Tests where the name includes a specific method at site A are mapped to methodless tests at site B • Works for the known use case • Either estimated weights or scale weights may be good enough for a particular study • This represents a loss of information when data moves from A to B

12. Proposed Best Practice • Always capture the method with the data if it is known • Best practice: Always map to the methodless LOINC code but always send the method as part the value of OBX.17 Observation Method • Related policy: The LOINC Committee will encourage and help develop a coded value set for methods • Allowed practice: Map to the LOINC code that precoordinates the method in the code • Discouraged practice: mapping tests where the method is known to methodless LOINC codes

13. Examples • Local test: Hepatitis C virus Ab.IgG by EIA • Best: send EIA as method in OBX • OBX|1|CE|16936-7^Hep C virus^LN|…|EIA|… • Allowed: Send precoordinated code for EIA method • OBX|1|CE|57006-9^Hep C virus EIA^LN|…||… • Discouraged: Method not sent • OBX|1|CE|16936-7^Hep C virus^LN|…||…

14. Proposal #3 Always map to the Quantitative code even if the lab is only sending the interpretation.

15. Proposed Best Practice • Always map to the quantitative LOINC code • Related policy: The LOINC Committee will discourage or deprecate the use of nominal or ordinal LOINC codes for concentrations • Send numbers when they exist as the value of OBX 5 • Send interpretations when they exist as the value of OBX 8 • One or the other or both of the numeric value and the interpretation can exist in a data instance

16. Examples • Local test: Cocaine in blood, with values of “positive” and “negative” • Best: Map to Cocaine Qn and send interpretive value in OBX.8 (Interpretation, was previously abnormal flag) • OBX|1|CE|72405-4^Cocaine MCncBldQn^LN|||||positive| • Anticipates future send of value and interpretation • OBX|1|CE|72405-4^Cocaine MCncBldQn^LN||4.0|ng/ml||positive| • Discouraged: Map to ACncOrd and send interpretation in OBX.5 • OBX|1|CE|16633-0^Cocaine ACncBldOrd^LN||positive||||

17. Discussion

18. Degrees of Interoperability • Degree I: Exact equivalence without translation • Same code, unit of measure, and value set • Data are mutually substitutable in all contexts of use • Degree II: Exact equivalence after translation • Unit of measure conversion (need UCUM) • Mass concentration to substance concentration conversion (need the molecular weight) • Pre and post coordination translation • Method as part of LOINC code versus method sent somewhere else in the message • Peak or trough as part of LOINC code versus peak and trough sent somewhere else in the message • Data are mutually substitutable in all contexts of use after translation

19. Degrees of Interoperability (cont) • Degree III: Context specific subsumption • A parent-child relationship exists between tests at the different institutions • Method specific tests roll up to methodless tests • IgM or IgG antibodies roll up to generic antibody • Data are mutually substitutable only in a specific context of use even after translation • Degree IV: No interoperability • No comparable data or information exists between or among institutions

20. Similar EDs should have similar LOINC codes, different LOINC codes mean inconsistency.