LOINCActiveObservation

LOINC Code 43138-7: Population size Investigation

43138-7 is a LOINC code used to identify Population size Investigation 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 Population size. It is commonly used with the system or sample type ^Population.

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 Population size. It is commonly used with the system or sample type ^Population.

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: Investigation

What it does not mean

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

Key facts

  • Population size Investigation
  • Population size
  • CLIN; Cnt; Count; Number; Point in time; QNT; Quan; Quant; Quantitative; Random

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

Population size InvestigationPopulation size InvestPopulation sizeCLINPopulation size, InvestigationNumPt

Frequently asked questions

Code details

Code43138-7
SystemLOINC
Display namePopulation size Investigation
DescriptionPopulation size
Short namePopulation size Invest
ComponentPopulation size
PropertyNum
TimingPt
System (specimen)^Population
ScaleQn
MethodInvestigation
ClassCLIN
Example units#
StatusACTIVE
Order/ObservationObservation

Flags

BillableNo
Valid clinical useNo

Source

SourceLOINC
Version2.82
Releasemain
First released2.16
Last changed2.48

Consumer names

Population size, Investigation

Part names

Population sizeNumPt^PopulationQnInvestigationNumber (count)Point in time (spot)

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 43138-7 | HealthAssure