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Extended-spectrum β-lactamase (ESBL) detection in serum/plasma by immunoassay

Published: August 9, 2026Updated: August 16, 2026

This test checks for the presence of ESBL-producing bacteria in your blood, which may make certain antibiotics less effective.

Quick summary

["ESBL detection helps guide antibiotic treatment if infections are suspected."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
85838-1
Short code
ESBL blaSHV gene Islt/Spm Ql
Synonyms
ESBL blaSHV gene Islt/Spm Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
molgen
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What This Test Measures

ESBL (extended-spectrum β-lactamase) is an enzyme produced by some bacteria that can resist common antibiotics like penicillin and cephalosporins. This test detects whether your blood contains bacteria that produce ESBL, which could affect how your doctor chooses antibiotics for infections.

Why It’s Done

Your doctor may order this test if you have symptoms of a bacterial infection, such as fever, chills, or signs of infection in a wound or urinary tract, especially if you’ve recently taken antibiotics or if the infection doesn’t improve with standard treatment.

Sample Collection

A blood sample is taken from a vein in your arm. The blood is processed to separate serum or plasma, which is then tested for ESBL-producing bacteria.

What to Expect Before the Test

No special preparation is needed, but inform your doctor about any recent antibiotics or allergies to medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

ESBL Screen (Serum/Plasma)

Frequently asked questions

When might I get my results?
Results are typically available within 24 to 48 hours, depending on lab processing times.
What does a positive result mean?
A positive result means your blood sample contains bacteria that produce ESBL, which may limit the effectiveness of certain antibiotics. Your doctor will discuss next steps, such as switching to a different antibiotic or further testing.
Can I take antibiotics before the test?
Yes, but inform your doctor immediately if you’ve taken antibiotics recently, as this may affect the test results.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy