LOINCActiveObservation

LOINC Code 8636-3: Q-T interval corrected

8636-3 is a LOINC code used to identify Q-T interval corrected 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 QTC interval. It is commonly used with the system or sample type Heart.

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 QTC interval. It is commonly used with the system or sample type Heart.

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

Q-T interval corrected
QTC interval
The purpose of calculating a corrected QT interval (QTc) is to normalize each individual QT measurement from a given study to a single measurement that would represent the QT interval if the patient had a heart rate of 60 beats per minute. Several formulas are available to calculate QTc, including the Bazett formula and the Fridericia formula. Bazett's formula is used most commonly, but for situations in which the patient's heart rate is significantly elevated, the Fridericia formula may yield a more accurate QTc that reflects the QTc that would have been obtained were the patient in normal sinus rhythm. [PMID23972343] Use this LOINC code to report a QTc without specifying a method. For QTc by Fridericia use 76634-5, and for QTc by Bazett use 76635-2.
Cardiac; Cardio; Cardiology; EKG; EKG.MEASUREMENTS; Electrocardiogram; Heart Disease; Hrt; Point in time; QNT; Q-T interval corrected; 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

Q-T interval correctedQTC intervalEKG.MEASTimePtHeartQn

Frequently asked questions

Code details

Code8636-3
SystemLOINC
Display nameQ-T interval corrected
DescriptionQTC interval
Short nameQ-T interval corrected
ComponentQTC interval
PropertyTime
TimingPt
System (specimen)Heart
ScaleQn
ClassEKG.MEAS
Example unitss
StatusACTIVE
Order/ObservationObservation

Flags

BillableNo
Valid clinical useNo

Source

SourceLOINC
Version2.82
Releasemain
First released1.0h(3)
Last changed2.73

Part names

QTC intervalTimePtHeartQnQ-T interval correctedTime (e.g. seconds)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 8636-3 | HealthAssure