2018-08-20 - OBSERVABLE Meeting

In case it helps inform further consideration of Item 5 (Observables for various flavours of 'snapshot' systolic and diastolic BP readings...), here is a cumulative report of how often, in a UK Primary Care setting and over the last six years, each of the various 'BP Observation' related codes was entered as a new EPR item. Or, more accurately, how often some code in some terminology was entered but for the same basic underlying clinical idea as the SNOMED codes quoted here, since none of this data was captured using SNOMED codes natively - my particular task is to work out how to migrate this historically captured data across to SNOMED, hence the recommendation to the IE that it consider the discrepancy between the set of codes for systolic vs diastolic BP.

In essence, the vast majority of the recording (70% of 1 billion data points) was recorded as a pair of data items, coded as one diastolic plus one systolic BP reading observation, and at a rate equivalent to one composite BP observable per citizen per year. It isn't necessarily the case that all these are true 'in clinic' random BP measurements; given current good clinical practice of now preferring to monitor BP via an average of serial (preferably ambulatory) readings over random clinic readings, there ought to be very many more uses of the codes for these average readings than there are, which causes me to suspect that many of the unspecified readings are actually averages.

A further 27% is recoded using an 'its a BP' code, which we may imagine will have a less directly computable and graphable text entry such as '120/80 mmHg'  attached to it, or alternatively possibly sometimes a qualitative result like 'normal'.

The remainder - 1.5% of the total volume but still 16M data items - are a variety of other ways of stating or recording actual, or occasionally target, BP. 

SNOMED CT SNOMED TERM TOTAL 
1091811000000102 Diastolic arterial pressure  371,506,330  (observable entity)
72313002 Systolic arterial pressure  371,500,780  (observable entity)
163020007 O/E - blood pressure reading  290,944,800  (finding)
24184005 Raised blood pressure reading  2,463,660  (finding)
413606001 Average home systolic blood pressure  1,089,750  (observable entity)
413605002 Average home diastolic blood pressure  1,072,710  (observable entity)
75367002 Blood pressure  1,061,230  (observable entity)
407554009 Sitting systolic blood pressure  1,033,910  (observable entity)
407555005 Sitting diastolic blood pressure  1,024,250  (observable entity)
163025002 O/E - BP reading normal  837,370  (finding)
400974009 Standing systolic blood pressure  775,530  (observable entity)
400975005 Standing diastolic blood pressure  753,840  (observable entity)
314463006 24 hour blood pressure  443,890  (observable entity)
163035008 Sitting blood pressure reading  436,130  (observable entity)
314449000 Average 24 hour systolic blood pressure  412,220  (observable entity)
314462001 Average 24 hour diastolic blood pressure  408,110  (observable entity)
163034007 Standing blood pressure reading  374,540  (observable entity)
163027005 O/E - BP reading raised  353,960  (finding)
315613000 Target diastolic blood pressure  336,220  (observable entity)
335661000000109 Self measured blood pressure reading  309,290  (observable entity)
315612005 Target systolic blood pressure  281,290  (observable entity)
2004005 Normal blood pressure  268,880  (finding)
314461008 Average day interval diastolic blood pressure  265,850  (observable entity)
314446007 Average day interval systolic blood pressure  264,340  (observable entity)
198081000000101 Ambulatory systolic blood pressure  209,070  (observable entity)
198091000000104 Ambulatory diastolic blood pressure  205,000  (observable entity)
163026001 O/E - BP borderline raised  198,840  (finding)
314445006 Average night interval systolic blood pressure  156,270  (observable entity)
314956000 Borderline blood pressure  156,190  (finding)
314460009 Average night interval diastolic blood pressure  156,120  (observable entity)
313005002 O/E - BP reading: no postural drop  125,240  (situation)
407556006 Lying systolic blood pressure  94,350  (observable entity)
407557002 Lying diastolic blood pressure  92,250  (observable entity)
163033001 Lying blood pressure reading  55,100  (observable entity)
170582005 O/E - check high BP  39,880  (finding)
271649006 Systolic blood pressure  38,280  (observable entity)
163032006 O/E - BP stable  37,240  (finding)
271650006 Diastolic blood pressure  33,850  (observable entity)
271870002 Low blood pressure reading  30,290  (disorder)
163029008 O/E - BP reading:postural drop  28,890  (finding)
502541000000105 [D]Blood pressure raised, hypertension not diagnosed  27,270  (context-dependent category)
314440001 Average systolic blood pressure  22,100  (observable entity)
314453003 Average diastolic blood pressure  21,360  (observable entity)
163023009 O/E - BP reading low  14,330  (disorder)
271648003 Postural drop in blood pressure  13,700  (finding)
163028000 O/E - BP reading very high  11,380  (finding)
314464000 24 hour systolic blood pressure  10,070  (observable entity)
163024003 O/E - BP borderline low  9,320  (disorder)
170581003 O/E - initial high BP  9,150  (finding)
45007003 Low blood pressure  9,020  (disorder)
928021000000108 Baseline blood pressure  8,340  (observable entity)
314465004 24 hour diastolic blood pressure  8,190  (observable entity)
170573004 Pre-treatment BP reading  7,910  (regime/therapy)
271871003 BP reading labile  6,830  (finding)
271651005 Stable blood pressure  6,080  (finding)
6797001 Mean blood pressure  5,300  (observable entity)
163036009 O/E - blood pressure decreased  4,510  (finding)
163021006 O/E - BP unrecordable  2,780  (finding)
163037000 O/E - BP labile  2,600  (finding)
251080003 Labile blood pressure  2,250  (finding)
314448008 Maximum 24 hour systolic blood pressure  2,100  (observable entity)
314459004 Maximum 24 hour diastolic blood pressure  2,060  (observable entity)
716579001 Baseline systolic blood pressure  1,800  (observable entity)
271645000 Blood pressure unrecordable  1,740  (finding)
716632005 Baseline diastolic blood pressure  1,700  (observable entity)
163022004 O/E - BP reading very low  1,040  (disorder)
314447003 Minimum 24 hour systolic blood pressure  920  (observable entity)
314456006 Minimum 24 hour diastolic blood pressure  920  (observable entity)
314439003 Maximum systolic blood pressure  680  (observable entity)
314443004 Maximum night interval systolic blood pressure  670  (observable entity)
314457002 Maximum night interval diastolic blood pressure  670  (observable entity)
38936003 [D]Blood pressure abnormal, not diagnostic NOS  600  (finding)
314452008 Maximum diastolic blood pressure  600  (observable entity)
314438006 Minimum systolic blood pressure  290  (observable entity)
314451001 Minimum diastolic blood pressure  290  (observable entity)

Per my action item associated with agenda item 5 above, the requester responded:

"Thank you for your query. I've discussed the above with Jeremy Rogers so considering your options for future requirements the following would be beneficial:

• Random systolic arterial blood pressure
• Random diastolic arterial blood pressure

But to manage current and historical data it would be beneficial to be able to record ‘Diastolic arterial pressure’ as it may not be known if this is random or an average reading.

This would enable the ability to record Diastolic arterial pressure to complete the already available 72313002|Systolic arterial pressure (observable entity)| concept.

The more generic concepts 271649006 | Systolic blood pressure (observable entity) and 271650006 | Diastolic blood pressure (observable entity) suggested don’t specify arterial pressure therefore may have been used to record venous pressure, impacting the data recorded and how this is retrievable in the record?"

CC: Farzaneh Ashrafi, Daniel Karlsson, Jeremy Rogers