What is False-negative tuberculin test is seen in all except: and explain in detail?
• Positive: A positive tuberculin test indicates hypersensitivity to tuberculoprotein, denoting infection with the tubercle bacilli or prior immunisation with BCG. The test becomes positive 4-6 weeks after infection or immunisation. Tuberculin allergy wanes gradually and disappears after 4-5 years in the absence of subsequent contact with the mycobacteria. In endemic areas, the allergy is maintained by repeated contacts with the bacilli. 
• Negative: Persons who have never had contact or been exposed to the tubercle bacilli are tuberculin-negative negative tests (anergy) may be seen in miliary tuberculosis, convalescence from some viral infections like measles, lymphoreticular malignancy, sarcoidosis, severe malnutrition, immunosuppressive therapy or impaired cell-mediated immunity. 
• False negative results may also be due to inactive PPD preparations and improper injection technique. 
• False positive reactions may be seen in infections with some relatated mycobacteria ('atypical' mycobacteria). 
 
Ref: Ananthanarayana 8th ed page 360