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Keratocyte count (from Tzanck smear)

Published: August 9, 2026Updated: August 17, 2026

A Tzanck smear is a microscopic examination of cells collected from a lesion, often used to identify abnormal cells like those found in herpes infections or other viral conditions.

Quick summary

["This test helps diagnose skin or mucous membrane infections by examining cell samples under a microscope."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
32187-7
Short code
Tzanck Smear Skin
Synonyms
Tzanck Smear Skin
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
22
Ref high
198
Critical range
0.5 N/A – 10000 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
tzanck-smear
CPT
82553
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 Is a Tzanck Smear Used For?

Tzanck smears are primarily used to detect herpes simplex virus (HSV) infections, including cold sores and genital herpes. They may also be used for other viral infections like varicella-zoster virus (chickenpox/shingles) or certain fungal or bacterial infections when cells are scraped from blisters or lesions.

How Is the Tzanck Smear Performed?

A healthcare provider gently scrapes cells from a blister or lesion and spreads them on a microscope slide. The sample is then stained and examined under a microscope to identify abnormal cells or viral particles.

What Does a Positive Tzanck Smear Indicate?

A positive result often shows multinucleated giant cells (characteristic of HSV) or inclusion bodies, which can confirm a viral infection. However, results alone may not always definitively diagnose the condition—additional testing (e.g., viral culture or PCR) may be needed for confirmation.

How Is the Test Interpreted?

Interpretation depends on the presence of specific cell types. For example, giant cells with intranuclear inclusions strongly suggest HSV infection. A healthcare provider will review the results in the context of your symptoms and medical history.

Reference range

Adult males: 22-198 U/L; Females: 22-198 U/LN/A

Specimen: serum

No special preparation required. Inform provider of any chest pain or symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Role in Diagnosis and Management

Short name

None

Frequently asked questions

Why might my doctor order a Tzanck smear?
Your doctor may recommend this test if you have symptoms like blisters, sores, or rashes that suggest a viral infection (e.g., cold sores, shingles, or herpes). It helps rule out infections that require specific treatments, such as antiviral medications for herpes.
What are the limitations of this test?
While Tzanck smears are useful for diagnosing certain viral infections, they are not always definitive. False negatives or positives can occur, especially if the sample is not representative of the infection. Other tests (like viral cultures or PCR) may be needed for confirmation.
Can this test be done at home?
No, Tzanck smears are performed in a clinical setting by a healthcare provider. You will need to visit a doctor or lab for the procedure, which involves collecting cells from a lesion under sterile conditions.
  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 17, 2026. · Read our editorial policy