ORC - Placer Group accessioned by Filler application

Short Description:

Need to carry in laboratory orders and results messages (OML, ORL, OUL, ORU) the identifier assigned by the filler application to a Placer Group (i.e. to the promise responding to this order group).

Use Case:

For mostlaboratories in Europe the laboratory requisition received on paper or electronically is usually a list of panels and tests ordered together by a physician for one common purpose (diagnostic, follow-up, pre-operative, prognostic …). This requisition is named the “Placer Group” both in V3 and v2.x.It shall be mentioned in the laboratory messaging with the ordering provider.

In v2.X this entity is represented by ORC-4 “Placer Group Number”, which carries the unique identifier assigned to that Placer Group by the placer application. In Europe, the LIS on the laboratory side accessions this Placer Group, and assigns a unique identifier to it, hence a “Placer Group Filler Number” which appears on every paper report produced by the LIS and is also present in every results message sent by the LIS to the ordering system as well as to any other intended recipients.

Moreover, the one-way electronic messaging “Lab results to EHR”, with the requisition coming to lab on paper (as in the HITSP Lab results to EHR use case)and the results sent on the wire, is quite common in Europe. In this use case there is scarcely a “placer group placer number” and the only significant identifier representing the placer group is the “Placer Group Filler Number”, which is necessarily communicated to the intended results recipients. Thus, in case of further human dialog needed between the recipient caregiver and the lab staff, the caregiver can reference this number to the lab, to make sure both parties talk of the same object.

This explains why, lab information systems at least in Europe, need to communicate their own number assigned to the placer group. This is for example the reason why LIS in the Netherlands have been misusing HL7 v2.x in the past years, using OBR-2 and OBR-3 as order group numbers, rather than order numbers. This is also one of the brakes to HL7 standard adoption by French labs.

Proposed solution:

In ORC segment, upgrade data type of ORC-4 “Placer Group Number” from EI to EIP.

The first subcomponent will be, as it has always been, the number assigned to the placer group by the placer application. The second component will be the number assigned to the same object by the filler application. Both subcomponents are optional.

Version 3 Mapping:

This number would be the id of the Fulfiller Promise responding to a Placer Group, which does not seem to be modelized in HL7 V3 LAB, R1 Result Topic, and should be added in R2.

This should be also taken in account when designing the promise messages responding to the Composite Order.

Justification of the proposal:

The other possible solutions could have been:

  • Change every order&observation message structure to insert a new segment on top of the OBSERVATION_REQUEST and SPECIMEN segment groups. This solution is far too invasive on the standard, and threatening backward compatibility
  • Append a new field to ORC segment, named “Placer Group Filler Number”, using data type EI. But then, nothing in the message would suggest that the two identifiers are paired.

The upgrade of data type EI to EIP appears to be the least invasive change, the most harmless for existing implementations, and the most consistent one for future implementations that will use this feature.

Detail of the solution:

All changes take place in chapter 4 (section numbering and content is taken from v2.7):

Section 4.5.1 (ORC segment tabular description)

SEQ / LEN / C.LEN / DT / OPT / RP/# / TBL# / ITEM# / ELEMENT NAME
1 / 2..2 / ID / R / 0119 / 00215 / Order Control
2 / EI / C / 00216 / Placer Order Number
3 / EI / C / 00217 / Filler Order Number
4 / EIP / O / 00218 / Placer Group Number

Section 4.5.1 ORC Use notes

a)placer order groups

The Standard supports a mechanism to collect several orders together in a group. Most often this is used to represent an "ordering session" for a single patient. A common use case is the grouping of laboratory batteries and tests ordered together by a physician for a patient with a common diagnostic goal (e.g. preoperative blood testing, diabetes follow-up …)

An order group is a list of orders (ORCs) associated with an ORC-4-placer group number. A group is established when the placer supplies a placer group number with the original order. or when the filler accessions the order group and supplies a filler group number with the received order. The order group may be identified by the placer or by the filler or by both applications. The order group consists of all the ORCs and order detail segments that have the same placer group number. Orders can be removed from the group using cancel, or added using the replacement or parentchild mechanisms, or using the assign number/number assigned mechanism. New orders cannot otherwise be added to the group.

Section 4.5.1.4 (Placer Group Number)

4.5.1.4 ORC-4 Placer Group Number (EIP) 00218

Components: <Placer Assigned Identifier (EI)> ^ <Filler Assigned Identifier (EI)>

Subcomponents for Placer Assigned Identifier (EI): <Entity Identifier (ST)> & <Namespace ID (IS)> & <Universal ID (ST)> & <Universal ID Type (ID)>

Subcomponents for Filler Assigned Identifier (EI): <Entity Identifier (ST)> & <Namespace ID (IS)> & <Universal ID (ST)> & <Universal ID Type (ID)>

Definition: This field contains a unique identifier for the Placer Group as referenced by the Placer application, the Filler application, or both. A Placer Group is a set of orders grouped together by the placer application, and subsequently identified by the placer application and/or by the filler application.

Components: <Entity Identifier (ST)> ^ <Namespace ID (IS)> ^ <Universal ID (ST)> ^ <Universal ID Type (ID)>

Definition: This field allows an order placing application to group sets of orders together and subsequently identify them. It is a case of an Entity Identifier data type (2.A.28).

The Within each of the two Subcomponents, the first component is a string that uniquely identifies all order groups from the given (placer or filler) application. A limit of fifteen (15) characters is suggested but not required. It is assigned by the placer application and may come from the same series as the placer order number of the ORC, but this is not required. The second through fourth components constitute a (placer or filler) application ID identical to the analogous components of ORC-2-placer order number or ORC-3-filler order number . Order groups and how to use them are described in detail in Section 4.5.1, "ORC – Common Order Segment."