Observations on Clinical LOINC

1. Observations on Clinical LOINC CG Chute 29 Sept 2003

2. Reason for visit… • Chris likes LOINC • He whined about some structure issues • Stan said: “Whine not, tell us do.” • Here as a friend of LOINC 2

3. Why does Chris care aboutLOINC Structure Usual reasons for wanting to use LOINC: • Cohort identification and retrieval • Decision support triggers • Outcome research, Quality improvement • Etc. • All require aggregation! 3

4. Aggregation over LOINC Codes • Management of each axis/component • Collapse across axes combinations • Not always trivial – Sodium Component • Would be helped enormously with Axes ontologies • Underway for lab LOINC (Steindel, et al.) 4

5. Granularity of LOINC codes • Well-grounded in lab LOINC “The level of detail in the LOINC definitions was intended to distinguish tests that are usually distinguished as separate test results within the master file of existing laboratory systems.” • Less obvious basis for Clinical LOINC • No Silver Book 5

6. Information model vs. Terminology model • What role does a LOINC code play? • Fill in an HL7 message “slot” • What is the boundary between the message structure and the clinical LOINC structure? • Should the boundary rest on capacity for trivial aggregations? (gime all BPs) 6

7. Structure in Clinical LOINCon the 6-part information model • Virtually all Clinical LOINC tests invoke the 6-part information model • 0.3% (21) have blank System component • Liberal but inconsistent use of “subclass” (period separator) and subtype names • The term “class” is inconsistent • LOINC class vs. analyte class 7

8. Enumerations about Clinical LOINCNot homogeneous • 5851 Clinical entries in LOINC v2.09 • 5390 (92%) have PT as Time Aspect • Distribution of Scale: 47 DOC 27 MULTI 1555 NAR 1000 NOM 172 ORD 6 ORDQN 3037 QN 6 SET 8

9. Should the 6-part model dominate in clinical LOINC? • Some concepts are very simple • Body mass, NOS; Height… • Perhaps most are complex, with more than 6 components • Bearing aggregation logics in mind, should all period/carrot (./^) delimiters be strippable? 9

10. Compound ExpressionsAmong 5851 Clinical entries 10

11. Frequency of Compound ExpressionsWithin Component 11

12. Frequency of Compound ExpressionsWithin Component 12

13. Some Components with two ^ separators • DIFFUSION CAPACITY.CARBON MONOXIDE^^ADJUSTED FOR HEMOGLOBIN • DIFFUSION CAPACITY^^ADJUSTED TO BODY CONDITIONS • TIDAL VOLUME.EXPIRED.SPONTANEOUS^^UNCORRECTED FOR COMPRESSIBLE GAS VOLUME.SETTING • TIDAL VOLUME.EXPIRED.SPONTANEOUS^ON VENTILATOR^CORRECTED FOR COMPRESSIBLE GAS VOLUME • TIDAL VOLUME.SPONTANEOUS+MECHANICAL^ON VENTILATOR^CORRECTED FOR COMPRESSIBLE GAS VOLUME • TIDAL VOLUME.SPONTANEOUS+MECHANICAL^ON VENTILATOR^CORRECTED FOR COMPRESSIBLE GAS VOLUME/BODY WEIGHT • TIDAL VOLUME.SPONTANEOUS+MECHANICAL^ON VENTILATOR^UNCORRECTED FOR COMPRESSIBLE GAS VOLUME • VOLUME^AT 1.0 S POST FORCED EXPIRATION^POST BRONCHODILATION • VOLUME^AT 1.0 S POST FORCED EXPIRATION^PRE BRONCHODILATION • VIEWS^W CONTRAST.XXX TRANSHEPATIC^W HEMODYNAMICS 13

14. Some Components with five . Separatorsand one with six • CAPACITY.VITAL.FORCED.POST BRONCHODILATION/CAPACITY.VITAL.FORCED PREDICTED • VOLUME.AT 25-75% OF FORCED EXPIRATION.MEASURED.POST BRONCHODILATION/VOLUME.AT 25-75% OF FORCED EXPIRATION.PREDICTED • VOLUME.AT 25-75% OF FORCED EXPIRATION.MEASURED.PRE BRONCHODILATION/VOLUME.AT 25-75% OF FORCED EXPIRATION.PREDICTED • BLOOD FLOW.MAX.STENOSIS.INTERNAL CAROTID ARTERY/BLOOD FLOW.MAX.UNOBSTRUCTED.COMMON CAROTID ARTERY 14

15. Hasty generalizations • The sub-syntax of clinical LOINC name components is complex (.^+/) • Composition syntax is wildly inconsistent • Parsing these puppies may mandate a call to the SPCA – not pretty 15

16. On ontologies • There do not appear to be consistent sets of terms from which clinical LOINC names are composed • Anatomy, timing, setting, adjustments • There do not appear to be consistent sub-axes within complex component names 16

17. So, What does Chris want done about it? Not a simple or easy problem • We must solve information/terminology model boundary problem • Exemplar issue of sub-message boundary • Template • Archetype • CEM (Clinical Expression Module) 17

18. Once the miracle occurs(model boundaries agreed upon) Clinical LOINC would be well advised to • Recognize it is not analogous to lab test name structures (no Silver book master) • Have a terminology RIM • Entertain DMIMs • Where truncation of element implies aggregation • Define terminology tables to populate slots • Hierarchies which support aggregation 18

19. On syntax • The 6-part model may not be optimal for such complex expressions • DMIMs imply variable size and shape of components • Use of delimiters (.^+/) should be rigorously consistent or abandoned • And/or must always aggregate by truncation • Perhaps will require XML or OWL structures 19

20. Historical analog • HL7 V2 was simple, spare, and usable • V2 did not scale well to complexity of clinical enterprise • Consistent and comparable messages are not dependable among V2 implementations • V3 imposes more rigorous formalisms to achieve comparable and consistent information interchange 20

21. Clinical LOINC (and other variants) • It may be time to consider “V3” style re-casting of the venerable LOINC structure • A formal, subset-able, terminology model may be desirable • One may chose to invoke Description Logic formalisms within element hierarchies • Syntax should evolve to correspond 21