When should a sputum specimen for acid-fast bacilli testing in TB be obtained?

The optimal time to collect a sputum specimen for acid-fast bacilli (AFB) testing in tuberculosis (TB) is early in the morning. This timing is significant because during the night, secretions and mucus accumulate in the lungs. Collecting a sample when the patient first wakes up ensures that the specimen is more concentrated and likely to contain the bacteria if present.

Morning specimens capture any pathogens that may have settled overnight, resulting in a higher yield for diagnostic testing. The process of collecting sputum should be done before the patient has eaten or engaged in any activities that could dilute the sample or affect its consistency, which can interfere with the results. Thus, early morning collection is standard practice in the diagnosis of TB through AFB testing.