Medknow Publications on behalf of Indian Association of Medical Microbiology
Abstract
Context: Search for a cost-effective, rapid and accurate test has
renewed interest in mycobacteriophage as a tool in the diagnosis of
tuberculosis (TB). There has been no reported data on the performance
of phage assay in a high burden, low-resource setting like Kanpur city,
India. Aims: To assess the sensitivity and specificity of the
FASTPlaque TBTM kit ability to impact the bacillary load in the phage
assay and its performance in the sputum smear sample negative cases.
Materials and Methods: The study involved a cross-sectional blinded
assessment of phage assay using the FASTPlaque TBTM kit on 68 suspected
cases of pulmonary TB against sputum smear microscopy by Ziehl-Neilsen
staining and culture by the LJ method. Results: The sensitivity,
specificity and positive and negative predictive values of the phage
assay were 90.7, 96, 97.5 and 85.7%, respectively. The assay was
negative in all the five specimens growing mycobacteria other than TB.
The sensitivity of the phage assay tended to decrease with the
bacillary load. Of the smear-negative cases, three were false negative,
and all of which were detected by the phage assay. Smear microscopy
(three smears per patient) had a sensitivity and specificity of 93 and
64%, respectively. Conclusions: The phage assay has the potential
clinical utility as a simple means of rapid and accurate detection of
live Mycobacterium tuberculosis bacilli; however, its performance has
been inconsistent across various studies, which highlights that the
assay requires a high degree of quality control demanding
infrastructure and its performance is vulnerable to common adversities
observed in "out of research" practice settings like storage, transport
and cross-contamination
