The Guilty, the Innocent, and the SNOMED Shuffle Attributes in transition

Currently accepted attributes  Causative agent  Associated etiologic finding  Temporally follows

Causative agent  Asserts A definitely caused by B  Accepts as values: Organisms Substances Physical forces

Examples Leprosy Causative agent Mycobacterium leprae Polybrominated biphenyl poisoning Causative agent Polybrominated biphenyl High altitude cerebral edema Causative agent Low air pressure Causative agent High altitude

Associated etiologic finding  Also asserts A definitely caused by B  Accepts as values Findings Disorders

Examples:  Graft failure due to thrombosis Associated etiologic finding Thrombosis  Iron deficiency anemia Associated etiologic finding Iron deficiency

Temporally follows  Asserts that A occurred after B  Neither asserts nor excludes causal relationship between A and B  Accepts as values Findings Disorders Procedures

Examples  Post-measles encephalitis Temporally follows Measles  Post-operative hemorrhage Temporally follows Surgical procedure

Problems and limitations:  Causality vs. association not always clear  Confusion between Associated etiologic finding and Temporally follows  Lack of generic “associated with” attribute  Cannot define a procedure as cause of a disorder or finding

Causality attributes appropriate if:  A is known to be caused by B  Causality keywords: due to caused by induced by resulting from

Ambiguous associations  Causality unclear in many cases  Keywords: associated with in with modified by during complicating secondary to

So how do I say: “A associated with B” ?  Use Temporally follows (old solution)  Use Associated with (proposed new solution)  DON’T! (preferred solution)

Temporally follows = associated with?  PRO Previously recommended Uses existing attribute  CON A and B may occur simultaneously Loss of “A POST B” as distinct meaning

Associated with  Proposed new attribute  Neither asserts nor excludes causality  Would be parent of: Causative agent Associated etiologic finding Temporally follows

Associated with  Pro: Unambiguous way to express ambiguous associations  Con Not yet accepted Potential overlap with Temporally follows

Proposed use of Associated with:  Will be used to express A + B without specifying nature of relationship between A and B  Examples: Tuberculosis in pregnancy AIDS with pneumonia

Why bother?  Good question! We DO NOT recommend using “Associated with” to post-coordinate concepts If you cannot specify the nature of the relationship between two concepts, do not conjoin them Enter as separate diagnoses or findings

Temporally follows vs. Associated with:  Potential overlap Both concepts neither assert nor exclude causality Temporally follows has been previously used to mean “associated with” Proposed new attribute hierarchy does not clearly define distinction between Temporally follows (may become “Sequela of”) and Associated with in use.

Temporally follows vs. Associated etiologic finding If A caused B, then by definition B preceded A (if only by a nanosecond). The lag in time between A and B, however, is often inapparent or insignificant.  Associated etiologic finding stresses causality  Temporally follows stresses time sequence

Proposed guideline: Use Temporally follows only when A necessarily follows B by a clinical significant period of time.  Keywords: after following post subsequent to

Example 1 Post-viral encephalitis Temporally follows Viral infection Occurs after resolution of viral infection Compare to: Viral encephalitis Causative agent Virus

Example 2 Post-operative hemorrhage Temporally follows Surgical procedure Compare to: Intra-operative hemorrhage Associated with Surgical procedure

Example 3 Post-streptococcal glomerulonephritis Temporally follows Streptococcal infection Associated etiologic finding Streptococcal infection If association is BOTH temporal and causal, both attributes are used.