diagnosis of tuberculosis using a dual gene target detection approach
Ehsan Aryan1, Fatemeh Estaji1,
Mahdi Kouhi-Noghondar1, Masoud Yousefi1, Zahra Meshkat1, Mohammad
Derakhshan1 and Bamdad Riahi-Zanjani2
Since conventional methods for diagnosis of
tuberculosis (TB) are
insensitive or time-consuming, a large number of PCR-based assays have
been introduced in recent years for rapid and sensitive diagnosis of TB
using different gene targets. The present study aimed at detecting two
popular targets, IS6110 and mpt64, simultaneously in clinical specimens
to improve the value of molecular diagnostics for Mycobacterium
tuberculosis complex (MTBC).
Resistance Research Center, Mashhad University of Medical Sciences,
Mashhad, Islamic Republic of Iran, 2Medical Toxicology Research Center,
Mashhad University of Medical Sciences, Mashhad, Islamic Republic of
In a cross-sectional study, specimens were collected from 167 patients
suspected of having TB who referred to Qaem hospital, Mashhad, Iran.
They fell into two TB (107 patients) and non-TB (60 patients) groups.
Using a 10-fold serial dilution of MTB DNA, analytical sensitivities of
IS6110- and mpt64-PCR were respectively ≥5 fg and ≥1 pg
equivalent to 200 and one copies of purified MTB DNA/reaction. Using a
10-fold serial dilution of MTB cells, the analytical sensitivity of
both assays was ≥170 CFU/ml relatively equivalent to 40 MTB
cells/reaction. Overall diagnostic sensitivities of IS6110- and
mpt64-PCR were 77.6% (CI, 68.5-85.1%) and 74.8% (CI, 65.5-82.7%),
respectively (p=0.72). According to our results, if both assays are
carried out on each clinical specimen, the overall sensitivity would
increase to 90.7% (CI, 83.5-95.4%) which is significantly higher than
that of IS6110-PCR (p=0.0005) and mpt64-PCR (p=0.0001) when are
Although IS6110 is a repetitive gene in MTB genome compared to mpt64,
its detection in clinical specimens by PCR is not significantly more
sensitive than that of mpt64. Remarkably, performing two PCR assays on
a clinical specimen each targeting IS6110 and mpt64 can significantly
improve the diagnostic value of PCR for TB.
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