At-Home In-Vitro Test Report
1.1.0 - STU 1.1

At-Home In-Vitro Test Report, published by HL7 International / Orders and Observations. This guide is not an authorized publication; it is the continuous build for version 1.1.0 built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/home-lab-report/ and changes regularly. See the Directory of published versions

## Technical Guidance

### Modeling

#### US Core Laboratory Report vs. US Core Diagnostic Report

The US Laboratory Observation Profile is intended to record or update single laboratory results (though it can also contain component results - see Multiplex Tests). An At-Home In-Vitro Test and Result is a “one at a time” test that is performed and resulted. Each test and result consists of a single test kit. A test kit can be a Multiplex Assay test that serves as a single test to diagnose infection caused by multiple viruses. Only one Observation is allowed per DiagnosticReport - that one Observation can contain multiple hasMembers that reference the results of the multiplex assay tests. The US Core Diagnostic Report Profile is used to group and summarize test results by reference. Public health agencies in most cases today, can only receive and record HL7 V2 messages. The V2 Lab Report message, by consensus, has been mapped to Diagnostic Report. Therefore, this guide has leveraged the US Core Diagnostic Report Profile to send this single result. In addition, it was necessary to leverage the FHIR SupportingInfo extension to hold answers to questions patients are asked by the app when recording or uploading their test results.

#### Multiplex tests

Multiplex Assay tests that serve as a single test to diagnose infection caused by multiple viruses (e.g. CDC Flu SC2 Multiplex Assay for SARS-CoV-2, influenza A, and/or influenza B viruses), use multiple Observation.hasMember to record each type of test in a reference to another Observation.

### Serial Testing

Based on updated guidance from FDA advising that tests be repeated multiple times conditioned on symptoms, the guidance to record this is to use Observation - Patient Question Answer to ask whether patient has previously taken a test and can then determine other tests and their sequence by finding other tests taken by patient and using date.

### RESTful FHIR Interactions Quick Start Guidance

Please see the US Core Quick start sections of each US Core profile for an overview of search and read operations for that profile.

### SMART App Launch

Please see SMART App Launch for guidance around SMART apps including IDs. This flow is not the same as an App that integrates with an EHR - so the sequence diagram is likely simpler.

### Extended Operations on the RESTful API

Please see Extended Operations on the RESTful API for guidance on a set of common interactions (read, update, search, etc.) performed on a repository of typed resources. These interactions follow the RESTful paradigm of managing state by Create/Read/Update/Delete actions on a set of identified resources.

### FHIR Bundle Resource

Given that the COVID-19 At-Home In-Vitro Test Report use case consists of a single test or series of tests, independently run by a patient, and is resulted from a "Lateral Flow Assay" device and then collected and/or sent by an App, there is no database (e.g. EHR database) from which referenced resources can be queried and returned. As such, any resource representing the lab result itself, "ask at order" (AOE) answers, etc. will need to be packaged together into a Bundle resource. As outlined in the Scope and Usage section of the Resource Bundle, the primary “bundling” function for this use case is “Sending a set of resources as part of a message exchange".

### Using OIDs as Identifiers

A numeric or alphanumeric string that is associated with a single object or entity within a given system. One type of identifier is an OID (object identifier). See the FHIR identifier data type guidance for further details on using OIDs as Identifiers, specifially the paragraph that discusses the case when the identifier value itself is naturally a globally unique URI.