A 24-year-old man undergoes a routine medical check-up to become a volunteer in the ER. PPD skin test shows an induration diameter of 9 mm. Sputum and chest X-ray are done; they are negative for tuberculosis. He is otherwise healthy and has no fever, cough, or other symptoms of Mycobacterium tuberculosis infection.
Question
What is the most appropriate explanation for the doubtful tuberculin test in this patient?
1 Sputum and chest X-ray report could be wrong.
2 Adequate sputum samples were not supplied.
3 He was given BCG vaccination earlier in life.
4 He may suffer from chronic cavitary lesion in the lung.
5 He has an active tubercular infection.