Organisms and other observations/tests are reported using multiple OBX segments. The granularity expected for HL7 culture reports is one observation per organism.
All OBX segments which have the same observation ID and sub-ID are part of a single observation.
Each organism in a culture battery is assigned a unique OBX-4-observation sub-ID (and is therefore a separate observation). The organism name is given in OBX-5-observation value (results). It is recommended, but not required that the organism name may change over time, but the corresponding observation sub-ID never changes. (The observation ID will be identical for all organisms reported.)
Recommended:
OBX||CE|organism^413^L|1|^E. Coli||||||F <CR>
OBX||CE|organism^413^L|2|^S. Aureus||||||F <CR>
Not recommended:
OBX||CE|organism1^413^L|1|^E. Coli||||||F <CR>
OBX||CE|organism2^413^L|1|^S. Aureus||||||F <CR>
Each antimicrobial should be reported as a separate (OBX) observation where the Observation ID is a code for the antimicrobial. (OBXs for non-antimicrobials observations and related information may be present in the same battery.)
MIC and disk diffusion (Kirby Bauer) susceptibility results can be combined in the same OBX segment. An OBX can contain an MIC value (in OBX-5-observation value (results)) and OBX-8-abnormal flag that indicates whether the organism is sensitive, resistant, or intermediate (see HL7 table 0078- Abnormal flags under abnormal flag fields).
Or, an OBX can contain a disk diffusion result string (e.g., sensitive) in the Observation Results field and the disk diffusion interpretation in OBX-8-abnormal flags (e.g., S).
A susceptibility battery may only contain results corresponding to a single organism that has been previously reported in a culture battery.
The following is the preferred, but not required method of organizing data about antimicrobial susceptibility.
A susceptibility battery may only contain results corresponding to a single organism that has been previously reported in a culture battery.
A susceptibility battery is always a child order to a culture battery. OBR-29-parent number (parents filler order number) in the susceptibility OBR is equal to OBR-3-filler order number in the parent culture OBR and is used to link the two batteries logically.
The susceptibility battery also contains a linkage back to a particular organism in the culture battery. OBR-26-parent result of the susceptibility OBR contains two components--OBX-3-observation identifier (code only) and OBX-4-observation sub-ID of the OBX in the culture battery which contains the organism name.
The identity of an organism/isolate is expected to be refined over time. When an organism identification changes, the parent culture battery can be resent without resending the child susceptibility battery.
The case may occur where a susceptibility battery is reported on an organism which has not yet been identified. In this case, it is required that a placeholder OBX for the organism name be reported in the corresponding culture battery so that OBR-26-parent result in the susceptibility OBR will point to a valid organism OBX in the culture battery. Transmission of an organism OBX (in the culture battery) with the Sub-ID field valued must precede the susceptibility battery which uses the identical Sub-ID in OBR-26-parent result.
Discussion and examples:
Order micro results (blood culture)
MSH|^~\&|LAB1||DESTINATION||19910127105114||ORU^R03|LAB1003929
PID|||900329493||PETRSN~DAVID|||927
PV1||I|
ORC|NW|
OBR||A485388^OE|H29847^LAB1|BLOOD CULTURE|||
Result for culture
ORC|RE...
OBR||A485388^OE|H29847^LAB1|BLOOD CULTURE||...
OBX||FT|SDES^SOURCE||BLOOD-RAPID||||||F <CR>
OBX||FT|EXAM^MICROSCOPIC||GRAM POSITIVE COCCI IN GROUPS||||||F <CR>
OBX||FT|ORGANISM^IDENTIFIER|1|ISOLATE 1||||||F <CR>
Result for susceptibility
ORC|RE...
OBR||A485388^OE|H29848^LAB1|BT1^SUSCEPTIBILITY BATTERY|||||MC|to field
... 26|ORGANISM^1|||A485388&OE^H29847&LAB1|
OBX||CE|ACAPEN^PENICILLIN||0.5|R|||||F <CR>
OBX||CE|ACHNAF^NAICILLIN||1|R|||||F <CR>
OBX||CE|ACHCCLI^CLINDAMYCIN||<=0.1|S|||||F <CR>
Result for Culture ID
ORC|RE...
OBR||A485388^OE|H29847^LAB1|BLOOD CULTURE||...
OBX||FT|ORGANISM^IDENTIFIER|1|STAPH EPI||||||F <CR>
New result for culture ID
ORC|RE...
OBR||A485388^OE|H29847^LAB1|BLOOD CULTURE||...
OBX||FT|ORGANISM^IDENTIFIER|1|STAPH EPI SERO TYPE 3||||||F <CR>
Assumptions
1. All OBXs in the parent order must employ the same coding scheme.
2. The Sub-ID of the parent OBXs (result) cannot change.