Objective        To explore the methodology of the phage amplified biologically assay (PhaB assay) using a newly isolated and identified mycobacteriophage named Chy2

and to evaluate its clinical value for detecting Mycobacterium tuberculosis (MTB) in sputum samples.       Methods        The optimal concentration and time of phage-inactivation agents were observed by spot tests. The optimal time and titer of phage to infect MTB were confirmed by plaque counts. Fifty-eight clinical sputum samp

les were collected from patients suspected with tuberculosis (TB) with no previous history of TB treatment

and were detected by PhaB assay using phage Chy2 and D29

respectively. Modified Lowenstein-Jensen (L-J) culture method was used as the diagnostic standard.        Results        Ferrous ammonium sulfate (FAS) solution (6%) mixed with Chy2 for 5 min was able to completely inactivate the extracellular phages. Chy2 of 2.2×10

11

CFU/mL could infect MTB most effectively after incubating with MTB for 4 hours. PhaB assay using Chy2 to detect MTB in sputum samples only needed 48 hours

and had sensitivity

specificity

Youden index

positive predictive value (PPV) and negative predictive value (NPV) of 94.7%

85.0%

0.797

0.923 and 0.895

respectively

while the counterparts of D29 PhaB assay were 76.3%

95.0%

0.713

0.967 and 0.678

respectively. Chy2-PhaB assay had a higher sensitivity and NPV than D29-PhaB assay did (P0.05).       Conclusion        PhaB assay using Chy2 has been successfully established with a similar specificity and a higher sensitivity for detecting MTB in sputum as compared with D29

and has the potential to be a valuable

rapid and economic screening approach for detecting pulmonary TB.