What is the purpose of adding NALC to the NaOH digestion when processing clinical specimens for tuberculosis?

• A. To mucolytically liquefy mucus and allow reduction of NaOH
• B. To increase decontamination
• C. To kill non-tuberculous mycobacteria
• D. To fix the sample

Answer: (A)

NALC is a mucolytic that breaks down thick mucus in respiratory specimens, turning it into a more liquid, homogeneous suspension so the bacilli are released from mucus and clumps. In the NaOH digestion, this mucolysis allows the alkali to act more effectively but need not be as harsh, enabling a reduction in the effective NaOH exposure while still decontaminating the sample. The result is better recovery of Mycobacterium tuberculosis because the bacilli are released from mucus and survive the processing rather than being trapped or killed by excessive alkali. Thus, the main purpose is to mucolytically liquefy mucus and permit reduction of NaOH.