What does this LOINC code represent?

This LOINC code identifies a lab observation, measurement, question, or clinical concept in a standardized format.

Is this enough to understand my test result?

No. The code identifies the test or observation, but the interpretation depends on the actual result, reference range, and clinical context.

LOINCActiveObservation

LOINC Code 16659-5: Corticotropin 2.5 Hr post Unsp challenge RIA (P) [Mass/Vol]

Name: LOINC Code 16659-5: Corticotropin 2.5 Hr post Unsp challenge RIA (P) [Mass/Vol]
Creator: HealthAssure Clinical Team
Published: 2026-05-21T11:17:26.379Z

16659-5 is a LOINC code used to identify Corticotropin 2.5 Hr post Unsp challenge RIA (P) [Mass/Vol] in laboratory and clinical observation data. You may see this code in lab systems, lab reports, EHR exports, interoperability feeds, or other structured clinical data exchanges. LOINC codes identify tests, measurements, observations, survey items, and clinical questions in a standardized way. It is associated with the component Corticotropin^2.5H post XXX challenge. It is commonly used with the system or sample type Plas.

Reviewed by HealthAssure Clinical TeamUpdated 21 May 2026

What is this code?

LOINC codes identify tests, measurements, observations, survey items, and clinical questions in a standardized way. It is associated with the component Corticotropin^2.5H post XXX challenge. It is commonly used with the system or sample type Plas.

When is it used?

Used in lab systems, EHRs, and clinical data exchange.
May identify a test, observation, survey item, or clinical document request rather than a diagnosis.
Status: ACTIVE
Order vs observation: Observation
Method: RIA

What it does not mean

The code identifies the observation or test, not the actual result.

Key facts

Corticotropin [Mass/volume] in Plasma by Radioimmunoassay (RIA) --2.5 hours post XXX challenge
Corticotropin^2.5H post XXX challenge
2.5h p chal; ACTH; Adrenocorticotrophic hormone; Adrenocorticotropin; After; c206; c74; CHEMISTRY.CHALLENGE TESTING; Cortrosyn; Level; Mass concentration; p chal; Pl; Plasma; Plsm; Point in time; PST; QNT; Quan; Quant; Quantitative; RADIOIMMUNOASSAY; Random; Rc206; Tumor marker

Where you may see this code

You may see this code in lab systems, lab reports, EHR exports, interoperability feeds, or other structured clinical data exchanges.

Common synonyms

Corticotropin 2.5 Hr post Unsp challenge RIA (P) [Mass/Vol]Corticotropin [Mass/volume] in Plasma by Radioimmunoassay (RIA) --2.5 hours post XXX challengeACTH 2.5h p chal Plas RIA-mCncCorticotropin^2.5H post XXX challengeCHALCorticotropin 2.5 hr after challenge, BloodMCnc

Frequently asked questions

Code details

Code16659-5

SystemLOINC

Display nameCorticotropin 2.5 Hr post Unsp challenge RIA (P) [Mass/Vol]

DescriptionCorticotropin^2.5H post XXX challenge

Short nameACTH 2.5h p chal Plas RIA-mCnc

ComponentCorticotropin^2.5H post XXX challenge

PropertyMCnc

TimingPt

System (specimen)Plas

ScaleQn

MethodRIA

ClassCHAL

Example unitspg/mL;ng/L

StatusACTIVE

Order/ObservationObservation

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released1.0l

Last changed2.40

Consumer names

Corticotropin 2.5 hr after challenge, Blood

Part names

Corticotropin^2.5H post XXX challengeMCncPtPlasQnRIAMass ConcentrationPoint in time (spot)PlasmaRadioimmunoassay (RIA)

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from LOINC. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.