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ACID-FAST SMEAR, MICROSCOPIC EXAMINATION OF AFB

Synonym(s):

​Acid-fast bacilli Smear, AFB Smear, TB Smear, Mycobacterial Smear, Ziehl-Neelsen Stain for Mycobacteria, ZN-stain for Mycobacteria

Lab Section Category

Description

Indications

Specimen Required

​Sputum, bronchoalveolar lavage, CSF, body fluid, tissue, pus etc

Storage and Transport

Method

​Smear prepared from digested, decontaminated and concentrated sample.


Screening: Auramine O stain. Fluorescent microscopy.
Confirmatory: Ziehl Nielsen stain.

Test Results

​Acid-fast bacilli seen (with quantitation) / No Acid-fast bacilli seen
Quantitation according to United States Centers for Disease Control and Prevention (CDC method)


Number of AFB seen  Report
Fuchsin stain (1000x) Fluorochrome stain (450x)  
0 0 No AFB seen
1-2/300F 1-2/70 F Doubtful *
1-9/100F 2-18/50F 1+
1-9/10F 4-36/10F 2+
1-9/F 4-36/F 3+
>9/F >36/F 4+

* Not considered positive. Smears are repeated from either the same or a second specimen.

Reference Interval / Value

Turnaround Time

​8 - 24 hours

Day(s) Test Set up

​Monday – Saturday

Remarks

Change History Notes

Others

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