ZN Stain for TB
The Ziehl-Neelsen (ZN) stain is a bacteriological staining technique used in cytopathology and microbiology to identify acid-fast bacilli, particularly members of the Mycobacterium genus
It is a standard diagnostic tool for rapid TB diagnosis and is used globally
Indications of the Test
The ZN stain is used for the microscopic examination of clinical samples for acid-fast bacilli, which include Mycobacterium tuberculosis, the causative agent of tuberculosis.
No specific patient preparation is required for the ZN stain. However, it is essential to provide clear instructions to the patient for the collection of appropriate samples, such as sputum or cerebrospinal fluid (CSF).
Typical Reference Values
The ZN stain has a lower limit of detection of 5 × 10^3 organisms/mL and can detect 60% to 70% of culture-positive samples.
However, its detection rate is low, ranging from 0 to 20% for CSF specimens. A modified ZN stain has been developed to improve the detection rate, requiring only 0.5 ml of CSF specimens.
Turn Around Time
The turn around time for the ZN stain is typically short, as it is a rapid diagnostic tool. However, the exact time frame may vary depending on the specific laboratory and testing conditions.
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