LOINCObservation

LOINC Code 4666-4: Osmotic fragility Ql (RBC)

4666-4 is a LOINC code used to identify Osmotic fragility Ql (RBC) 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 Osmotic fragility. It is commonly used with the system or sample type RBC.

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 Osmotic fragility. It is commonly used with the system or sample type RBC.

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: DEPRECATED
  • Order vs observation: Observation

What it does not mean

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

Key facts

  • Deprecated Osmotic fragility
  • Osmotic fragility
  • Erythrocytes; Frag; Fragil; HEMATOLOGY/CELL COUNTS; Number Fraction; OF; Ordinal; Osmo; Osmo Frag; Percent; Point in time; QL; Qual; Qualitative; Random; Red blood cells; Red blood corpusles; Screen

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

Osmotic fragility Ql (RBC)Deprecated Osmotic fragilityDeprecated OF Fr RBCOsmotic fragilityHEM/BCOsmotic fragility, Red blood cellsNFr

Frequently asked questions

Code details

Code4666-4
SystemLOINC
Display nameOsmotic fragility Ql (RBC)
DescriptionOsmotic fragility
Short nameDeprecated OF Fr RBC
ComponentOsmotic fragility
PropertyNFr
TimingPt
System (specimen)RBC
ScaleOrd
ClassHEM/BC
StatusDEPRECATED
Order/ObservationObservation

Flags

BillableNo
Valid clinical useNo

Source

SourceLOINC
Version2.82
Releasemain
First released1.0
Last changed2.46

Consumer names

Osmotic fragility, Red blood cells

Part names

Osmotic fragilityNFrPtRBCOrdNumber FractionPoint in time (spot)Red Blood Cells

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.

LOINC Code 4666-4 | HealthAssure