We use cookies to understand how you use our site and to improve your experience. This includes personalizing content and advertising. To learn more, click here. By continuing to use our site, you accept our use of cookies. Cookie Policy.

Features Partner Sites Information LinkXpress
Sign In
Advertise with Us
LGC Clinical Diagnostics

STANDARD DIAGNOSTICS INC.

Standard Diagnostics develops rapid diagnostic tests that make it possible to diagnose various diseases at an earlier... read more Featured Products: More products

Download Mobile App




Rapid TB Test Accuracy Compromised by Mycobacterial Diversity

By LabMedica International staff writers
Posted on 27 Jul 2016
Print article
Image: The Bioline TBAg MPT64 rapid immunochromatographic identification test for the M. tuberculosis complex (Photo courtesy of Standard Diagnostics).
Image: The Bioline TBAg MPT64 rapid immunochromatographic identification test for the M. tuberculosis complex (Photo courtesy of Standard Diagnostics).
Throughout the world, Mycobacterium tuberculosis (Mtb) is responsible for the vast majority of tuberculosis (TB) cases; however, there are several other closely related mycobacterial species that cause TB, all part of the Mycobacterium tuberculosis complex (Mtbc).

Diagnostics for rapid confirmation of positive liquid cultures presumptive of M. tuberculosis bacteria, based on the detection of the MPT64 antigen, and are being used in many TB diagnostic laboratories worldwide. The diagnostic performance of these tests in West Africa, where TB is uniquely caused by the geographically restricted Mycobacterium africanum (Maf 1 and 2) and M. tuberculosis lineages, has not been properly assessed.

An international team of scientists led by those from the Medical Research Council (MRC) Unit, (Serrekunda, The Gambia) collected sputum samples prospectively from individuals with suspected TB between April and October 2014 and were all initially screened for the presence of acid fast bacilli (AFB) by Auramine microscopy. They compared the abundance of mpt64 gene product in sputum samples of patients with untreated pulmonary TB caused by Maf 2, the strain common in The Gambia or Mtb.

The scientists then prospectively analyzed culture isolates from 173 patients with one of the rapid tests, the BD MGIT TBc Identification test kit (Becton Dickinson Microbiology Systems, Sparks, MD USA). They repeated the same analysis with all samples that had tested negative on day zero and a random set of those that had tested positive using the SD Bioline Ag MPT64 Rapid test (Standard Diagnostics, Yongin-si, Republic of Korea). They observed no significant difference between the two tests. Gene expression of mpt64 gene was performed using multiplex real-time polymerase chain reaction (qPCR).

The team found that 150 of the samples tested positive on day zero (the day when mycobacterial growth in culture was first recorded), with 23 (13.2%) testing negative at this time point. The accuracy was much higher (over 90%) for the Mtb samples, compared with less than 80% for the Maf 2 samples. At Day 10, 84% of Maf 2 samples tested positive compared with 98% of Mtb samples. By Day 90, 98% of both Mtb and Maf 2 samples tested positive. Based on these results, 22% of Maf 2 patients, and 10% of Mtb patients would have been wrongly classified as having non-TB mycobacteria if the tests had not been repeated after day zero. At the end of the 10-day window recommended by the BD MGITTM TBc ID manufacturer, 16% of all Maf 2 samples remained negative, compared with only 2% of Mtb samples.

The authors indicated that MPT64 tests need to be cautiously used in settings where Maf 2 is common. However, they also recognize that given the relatively low cost, limited technical expertise and shorter turnaround time associated with using rapid speciation tests compared to alternative speciation methods, MPT64 rapid tests will likely remain one of the preferred options for timely diagnosis of suspected TB despite the possibility of false negative results, and suggest that a negative MPT64 result would require confirmation by an alternative method. The study was published on July 7, 2016, in the journal PLOS Neglected Tropical Diseases.

Related Links:
Medical Research Council
Becton Dickinson
Standard Diagnostics
Platinum Member
COVID-19 Rapid Test
OSOM COVID-19 Antigen Rapid Test
Specimen Collection & Transport
Anti-Cyclic Citrullinated Peptide Test
GPP-100 Anti-CCP Kit
Gold Member
Xylazine Immunoassay Test
Xylazine ELISA

Print article

Channels

Clinical Chemistry

view channel
Image: Reaching speeds up to 6,000 RPM, this centrifuge forms the basis for a new type of inexpensive, POC biomedical test (Photo courtesy of Duke University)

POC Biomedical Test Spins Water Droplet Using Sound Waves for Cancer Detection

Exosomes, tiny cellular bioparticles carrying a specific set of proteins, lipids, and genetic materials, play a crucial role in cell communication and hold promise for non-invasive diagnostics.... Read more

Molecular Diagnostics

view channel
Image: The study showed the blood-based cancer screening test detects 83% of people with colorectal cancer with specificity of 90% (Photo courtesy of Guardant Health)

Blood Test Shows 83% Accuracy for Detecting Colorectal Cancer

Colorectal cancer is the second biggest cause of cancer deaths among adults in the U.S., with forecasts suggesting 53,010 people might die from it in 2024. While fewer older adults are dying from this... Read more

Hematology

view channel
Image: The Gazelle Hb Variant Test (Photo courtesy of Hemex Health)

First Affordable and Rapid Test for Beta Thalassemia Demonstrates 99% Diagnostic Accuracy

Hemoglobin disorders rank as some of the most prevalent monogenic diseases globally. Among various hemoglobin disorders, beta thalassemia, a hereditary blood disorder, affects about 1.5% of the world's... Read more

Industry

view channel
Image: These new assays are being developed for use on the recently introduced DxI 9000 Immunoassay Analyzer (Photo courtesy of Beckman Coulter)

Beckman Coulter and Fujirebio Expand Partnership on Neurodegenerative Disease Diagnostics

Beckman Coulter Diagnostics (Brea, CA, USA) and Fujirebio Diagnostics (Tokyo, Japan) have expanded their partnership focused on the development, manufacturing and clinical adoption of neurodegenerative... Read more
Copyright © 2000-2024 Globetech Media. All rights reserved.