Evaluation of Loopamp Assay for the Diagnosis of Pulmonary Tuberculosis in Cambodia

Abstract

The Loopamp™ MTBC kit (TB-LAMP) is recommended by WHO for Mycobacterium tuberculosis complex detection in low-income countries with a still low drug-resistant tuberculosis (TB) rate. This study is aimed at testing its feasibility in Cambodia on sputa collected from presumptive tuberculosis patients. 499 samples were tested at a smear microscopy center and 200 at a central-level mycobacteriology laboratory. Using mycobacterial cultures as reference, TB-LAMP results were compared with those of LED fluorescent microscopy (LED-FM) and Xpert® MTB/RIF. At the microscopy center, TB-LAMP sensitivity was higher than that of LED-FM (81.5% [95% CI, 74.5-87.6] versus 69.4% [95% CI, 62.2-76.6]), but lower than that of the Xpert assay (95.5% [95% CI 92.3-98.8]). At the central-level laboratory, TB-LAMP sensitivity (92.8% [95% CI, 87.6-97.9]) was comparable to that of Xpert (90.7% [95% CI, 85.0-96.5]) using stored sample. No significant difference in terms of specificity between TB-LAMP and Xpert assays was observed in both study sites. In conclusion, our data demonstrate that TB-LAMP could be implemented at microscopy centers in Cambodia to detect TB patients. In addition, TB-LAMP can be a better choice to replace smear microscopy for rapid TB diagnosis of new presumptive TB patients, in settings with relative low prevalence of drug-resistant TB and difficulties to implement Xpert assay.

Point-of-care test for tuberculosis - a boon in diagnosis

“…Several miniaturized LAMP techniques, such as microfluidic, electrochemical, paperbased, and digital methods, have been developed for rapid sample processing and screening of pathogens [19]. One of the studies evaluated the efficiency of the WHO-approved TB-LAMP kit in a sputum sample of TB patients in LMIC and indicated its potential to be used at microscopy centers in a resource-limited setting [20]. Similarly, another study demonstrated the good sensitivity and specificity of TB-LAMP for Mtb detection in LMICs [21].…”

Ultrafast, One-Step, Label-Based Biosensor Diagnosis Platform for the Detection of Mycobacterium tuberculosis in Clinical Applications

“…The SSM method is time-saving but lacks sensitivity. 7,9 Due to the time-consuming nature or low sensitivity of the traditional methods, developing an early diagnosis strategy is challenging, making it easy for TB patients to miss the optimal treatment window. In recent decades, many molecular methods, including conventional PCR and PCR-based techniques (namely, multiplex PCR, GeneXpert, and real-time PCR assays), have been used for the detection of MTB in clinical applications.…”

“…Mycobacterium culture, as a gold standard, is widely performed for the diagnosis of MTB. , Although mycobacterial culture is able to accurately identify MTB strains, the detection process is time-consuming (typically 4–8 weeks) and complicated (involving steps of isolation and identification), which cannot meet the demands of rapid detection. The SSM method is time-saving but lacks sensitivity. , …”

“…To address the issues of technical complexity and time consumption for PCR and PCR-based techniques, loop-mediated isothermal amplification (LAMP), a fast, reliable, simple, and sensitive detection method, has been established and used to detect many pathogens (e.g., bacteria, viruses, fungi, and parasites). − At present, conventional LAMP techniques have proven to be effective in detecting MTB, but the validation methods for LAMP amplicons usually involve agarose gel electrophoresis, visual detection, and real-time turbidity. ,, Although the above three validation methods have been proven to be effective for conventional single LAMP assays, they are difficult to use to accurately identify amplification products from multitarget LAMP assays (namely, multiplex LAMP). With the advancement of nanomaterials, a biosensor using gold nanoparticles has been developed and used in the field of molecular detection [nanoparticle-based lateral flow immunoassay (LFIA) biosensor].…”