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.

LOINCActiveBoth

LOINC Code 2557-7: Lecithin/Sphingomyelin (Amn fld) [Mass ratio]

Name: LOINC Code 2557-7: Lecithin/Sphingomyelin (Amn fld) [Mass ratio]
Creator: HealthAssure Clinical Team
Published: 2026-05-25T17:13:11.347Z

2557-7 is a LOINC code used to identify Lecithin/Sphingomyelin (Amn fld) [Mass ratio] 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 Lecithin/Sphingomyelin. It is commonly used with the system or sample type Amnio fld.

Reviewed by HealthAssure Clinical TeamUpdated 25 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 Lecithin/Sphingomyelin. It is commonly used with the system or sample type Amnio fld.

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: Both

What it does not mean

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

Key facts

Lecithin/Sphingomyelin [Mass Ratio] in Amniotic fluid
Lecithin/Sphingomyelin
AF; Amn; Amn fl; Amnio; Amniotic flu; Amniotic fluid; c470; Chemistry; Choline phosphoglyceride; Mass concentration ratio; Mass ratio; MCRto; Phosphatidylcholine; Point in time; QNT; Quan; Quant; Quantitative; Random; SPH

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.

Related SNOMED CT concepts

705114005SNOMED CT mapping for Lecithin/Sphingomyelin (Amn fld) [Mass ratio] (2557-7)

Related observations and tests

SNOMED_CT 705114005high

LOINC Code System

Source: LOINC-SNOMED cooperation package

Common synonyms

Lecithin/Sphingomyelin (Amn fld) [Mass ratio]Lecithin/Sphingomyelin [Mass Ratio] in Amniotic fluidLecithin/Sphingomyelin AmnLecithin/SphingomyelinCHEMLecithin/Sphingomyelin, Amniotic fluidMRto

Frequently asked questions

Code details

Code2557-7

SystemLOINC

Display nameLecithin/Sphingomyelin (Amn fld) [Mass ratio]

DescriptionLecithin/Sphingomyelin

Short nameLecithin/Sphingomyelin Amn

ComponentLecithin/Sphingomyelin

PropertyMRto

TimingPt

System (specimen)Amnio fld

ScaleQn

ClassCHEM

StatusACTIVE

Order/ObservationBoth

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released1.0

Last changed2.73

Consumer names

Lecithin/Sphingomyelin, Amniotic fluid

Part names

Lecithin/SphingomyelinMRtoPtAmnio fldQnMass RatioPoint in time (spot)Amniotic fluid

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.