Ziehl-Neelsen (ZN) Stain Test

Synonyms

None

Purpose

Ziehl-Neelsen (ZN) stain is a rapid and practical method for detecting acid-fast bacilli (AFB). The test is usually ordered for people with symptoms of active tuberculosis.

Patient Preparation

The sputum should be evenly spread over the central area of the slide using a continuous rotational movement.

Samples

5 – 10ml of Sputum collected in a sterile screw-cap container. First morning specimens are preferred due to overnight accumulation of secretions. Refrigerate at 2°C to 8°C.

Reference Range

Sputum smear is graded as scanty”,” 1+”,” 2+”,” and 3+. No AFB seen while observing more than 300 fields reported as No AFB seen. 1-9 AFB/100 fields report the exact number. 10-99 AFB/ 100 fields reported as 1+. 1-10 AFB/field at least in 50 fields reported as 2+. More than 10 AFB/field at least in 20 fields reported as 3+

Results Turnaround

1 – 2days after receipt of samples.

Diseases / Diagnostic indicators

Detection of acid-fast bacilli (AFB) in stained and acid-washed smears examined microscopically may provide the initial bacteriologic evidence of the presence of mycobacteria the clinical specimen. Mycobacteria is associated with tuberculosis and leprosy.