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 49929-3: Protein in pleural fluid/Protein in serum (S/P+Pleur fld) [Relative ratio]

Name: LOINC Code 49929-3: Protein in pleural fluid/Protein in serum (S/P+Pleur fld) [Relative ratio]
Creator: HealthAssure Clinical Team
Published: 2026-05-21T08:59:33.944Z

49929-3 is a LOINC code used to identify Protein in pleural fluid/Protein in serum (S/P+Pleur fld) [Relative 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 Protein.plr fld/Protein.serum. It is commonly used with the system or sample type Ser/Plas+Plr fld.

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 Protein.plr fld/Protein.serum. It is commonly used with the system or sample type Ser/Plas+Plr 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: Observation

What it does not mean

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

Key facts

Protein in pleural fluid/Protein in serum

Protein.plr fld/Protein.serum

Chemistry; PF/S PROT ratio; Pl; Plasma; Pleural; Pleural fluid; Plsm; Point in time; PR; Prot; Prot Plr; Prot PlrSerPl; QNT; Quan; Quant; Quantitative; Random; Relative ratio; Ser; SerP; SerPl; SerPl+Plr; SerPlas; Serum; Serum or plasma; SR; thoracentesis fluid

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

Protein in pleural fluid/Protein in serum (S/P+Pleur fld) [Relative ratio]Protein in pleural fluid/Protein in serumProt Plr/SerPlProtein.plr fld/Protein.serumCHEMProtein in pleural fluid/Protein in Serum, S/P+Pleur FldRelRto

Frequently asked questions

Code details

Code49929-3

SystemLOINC

Display nameProtein in pleural fluid/Protein in serum (S/P+Pleur fld) [Relative ratio]

DescriptionProtein.plr fld/Protein.serum

Short nameProt Plr/SerPl

ComponentProtein.plr fld/Protein.serum

PropertyRelRto

TimingPt

System (specimen)Ser/Plas+Plr fld

ScaleQn

ClassCHEM

Example unitsRatio

StatusACTIVE

Order/ObservationObservation

Flags

BillableNo

Valid clinical useNo

Source

SourceLOINC

Version2.82

Releasemain

First released2.22

Last changed2.73

Consumer names

Protein in pleural fluid/Protein in Serum, S/P+Pleur Fld

Part names

Protein.plr fld/Protein.serumRelRtoPtSer/Plas+Plr fldQnRelative RatioPoint in time (spot)Serum or Plasma and Pleural 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.