title: Phenol-ammonium sulfate microscopy method for diagnosis of pulmonary tuberculosis.
abstract: BACKGROUND
  Collection and processing of sputum samples for the detection of acid fast bacilli (AFB) is hazardous for health-workers in developing countries with limited facilities. The phenol ammonium sulfate (PhAS) method involves smear microscopy and Ziehl-Neelson (ZN) staining of precipitates/ floccules formed in sputum samples when PhAS is added. The present study has been designed to assess the performance and safety of this method.
  
  
  METHODS
  The study was conducted from January 2011 to March 2011 at the Department of Microbiology, Lala Ram Sarup Institute of Tuberculosis and Respiratory Diseases, New Delhi. A total of 1038 sputum samples were subjected to ZN staining before and after treatment with PhAS. The smear microscopy results of the PhAS treated and untreated samples were compared. In addition, 200 representative samples were inoculated after processing by petroff's method directly for culture and after treatment with PhAS.
  
  
  RESULTS
  The sensitivity, specificity, positive predictive value and negative predictive value of the PhAS solution treated ZN smear microscopy method were found to be 98.8%, 88.5%, 98.0% and 92.7% respectively in comparison with direct smear microscopy. The overall correlation between the two methods was found to be 97.3%. None of the PhAS treated samples grew Mycobacterium tuberculosis on culture.
  
  
  CONCLUSIONS
  Sputum microscopy with PhAS solution is a safe, reliable and inexpensive alternative for direct microscopy. This method can be conveniently applied for usage in microscopy centers with limited bio-safety facilities.
authors.affiliation: Department of Microbiology, Lala Ram Sarup Institute of Tuberculosis and Respiratory Diseases, New Delhi 110030, India.
authors.forename: Ritu
authors.initials: R
authors.lastname: Singhal
authors.affiliation: Department of Microbiology, Lala Ram Sarup Institute of Tuberculosis and Respiratory Diseases, New Delhi 110030, India.
authors.forename: Manpreet
authors.initials: M
authors.lastname: Bhalla
authors.affiliation: Department of Microbiology, Dr. A.L.M (P.G) Institute of Basic Medical Sciences, University of Madras, Sekkizhar Campus, Taramani, Chennai 600113, Tamil Nadu, India.
authors.forename: Sujeet
authors.initials: S
authors.lastname: Chakraborty
authors.affiliation: Department of Microbiology, Lala Ram Sarup Institute of Tuberculosis and Respiratory Diseases, New Delhi 110030, India.
authors.forename: Niti
authors.initials: N
authors.lastname: Singh
authors.affiliation: Department of Pulmonary Medicine, Post Graduate Institute of Medical Research, Chandigarh, India.
authors.forename: Digamber
authors.initials: D
authors.lastname: Behera
authors.affiliation: Department of Microbiology, Lala Ram Sarup Institute of Tuberculosis and Respiratory Diseases, New Delhi 110030, India. Electronic address: ritugo@hotmail.com.
authors.forename: Vithal Prasad
authors.initials: VP
authors.lastname: Myneedu
keywords: Acid-fast; Ammonium-sulphate; Microscopy; Mycobacterium; Phenol; Sputum