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 55477-4: E2 4 Hr post Unsp challenge [Moles/Vol]

Name: LOINC Code 55477-4: E2 4 Hr post Unsp challenge [Moles/Vol]
Creator: HealthAssure Clinical Team
Published: 2026-05-21T08:59:37.765Z

55477-4 is a LOINC code used to identify E2 4 Hr post Unsp challenge [Moles/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 Estradiol^4H post XXX challenge. It is commonly used with the system or sample type Ser/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 Estradiol^4H post XXX challenge. It is commonly used with the system or sample type Ser/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

What it does not mean

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

Key facts

Estradiol (E2) [Moles/volume] in Serum or Plasma --4 hours post XXX challenge
Estradiol^4H post XXX challenge
17-beta estradiol; 4h p chal; After; CHEMISTRY.CHALLENGE TESTING; E2; Level; Oestradiol; p chal; Pl; Plasma; Plsm; Point in time; PST; QNT; Quan; Quant; Quantitative; Random; SerP; SerPl; SerPlas; Serum; Serum or plasma; SR; Substance concentration

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

E2 4 Hr post Unsp challenge [Moles/Vol]Estradiol (E2) [Moles/volume] in Serum or Plasma --4 hours post XXX challengeEstradiol 4h p chal SerPl-sCncEstradiol^4H post XXX challengeCHALEstradiol 4 hr after challenge, BloodSCnc

Frequently asked questions

Code details

Code55477-4

SystemLOINC

Display nameE2 4 Hr post Unsp challenge [Moles/Vol]

DescriptionEstradiol^4H post XXX challenge

Short nameEstradiol 4h p chal SerPl-sCnc

ComponentEstradiol^4H post XXX challenge

PropertySCnc

TimingPt

System (specimen)Ser/Plas

ScaleQn

ClassCHAL

Example unitspmol/L

StatusACTIVE

Order/ObservationObservation

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released2.27

Last changed2.36

Consumer names

Estradiol 4 hr after challenge, Blood

Part names

Estradiol^4H post XXX challengeSCncPtSer/PlasQnSubstance ConcentrationPoint in time (spot)Serum or Plasma

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.