Experience with a simplification of the petroff method for laboratory diagnosis of mycobacteria in sputum.

In the original Petroff procedure sputum is digested with NaOH and the centrifuged deposit neutralized with HCl before culturing. A modification in which digestion is arrested by dilution with water and the sediment is seeded on buffered media is simpler, quicker, safer and in our hands seems to give a greater number of positive smears and cultures for mycobacteria with less overgrowth by contaminants. The usefulness of regular smear examinations for excluding tuberculosis in nonspecific chest complaints is questioned.