Limit of detection, limit of quantification and limit of blank

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Limit of detection, limit of quantification and limit of blank

Transcript Of Limit of detection, limit of quantification and limit of blank

Eurachem

A FOCUS FOR ANALYTICAL CHEMISTRY
IN EUROPE

Limit of detection, limit of quantification and limit of blank
Elvar Theodorsson

LoB, LoD, LoQ
• Limit of blank (LoB), limit of decision, limit of detection (LoD) and limit of quantitation (LoQ) and are concepts and terms used to describe the lowest concentration of a measurand that can be reliably measured by a particular measurement procedure .
• The literature in this area has previously been and is unfortunately still confusing regarding concepts, nomenclature and methods.
• The approach recommended here is primarily based on recent recommendations by Eurachem
https://www.eurachem.org/images/stories/Guides/pdf/MV_guide_2nd_ed_EN.pdf

CLSI - IFCC

Imprecision profile

Common notion of limit of quantitation in clinical chemistry
• The concentration at which imprecision (coefficient of variation) of the method is 5%
However
• Medical laboratories are already and increasingly faced with the question of the possible presence of a measurand for medical (tumor markers, infectious agents, carcinogens, pollutants) or legal reasons (drugs of abuse). More formal understanding of the detection limit and limit of quantitation is therefore needed

Detection limit is basically a familiar concept

Absence of disease Absence of measurand = blank

Persons with disease Measurand present

Detection limit is basically a familiar concept

Positive test Negative test

Participants

With disease True positives

Without disease False positives (type I error)

False negatives True negatives (type II error)

Total with disease

Total without disease

[Sensitivity] [Specificity]

Total positive
Total negative

[PPV] [NPV]

Three levels
• Decision limit, limit of blank, critical value
• CCα (term used in the EU directives) • LOD
• Limit of Detection, minimum detectable value, detection limit, CCβ (term used in the EU directives)
• LOQ • quantification limit, quantitation limit, limit of quantitation, limit of determination, reporting limit, limit of reporting and application limit.
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Critical value in clinical chemistry
• The concept critical value in the context of detection should be used with care in clinical chemistry since it is most commonly used to denote the concentration at which the laboratory needs to notify the clinic in an extraordinary manner
LimitDetectionDiseaseDetection LimitQuantitation