Accurate and rapid diagnostic tests are critical for achieving control of coronavirus disease 2019 (covid-19), a pandemic illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Diagnostic tests for covid-19 fall into two main categories: molecular tests that detect viral RNA, and serological tests that detect anti-SARS-CoV-2 immunoglobulins. Reverse transcriptase polymerase chain reaction (RT-PCR), a molecular test, has become the gold standard for diagnosis of covid-19; however, this test has many limitations that include potential false negative results, changes in diagnostic accuracy over the disease course, and precarious availability of test materials. Serological tests have generated substantial interest as an alternative or complement to RT-PCR and other Nucleic acid tests in the diagnosis of acute infection, as some might be cheaper and easier to implement at the point of care. A clear advantage of these tests over RT-PCR is that they can identify individuals previously infected by SARS-CoV-2, even if they never underwent testing while acutely ill. Many serological tests for covid-19 have become available in a short period, including some marketed for use as rapid, point-of-care tests. The pace of development has, however, exceeded that of rigorous evaluation, and important uncertainty about test accuracy remains.
Although the use of LED-FM only marginally increased sensitivity, the considerable time saving ability combined with very good acceptance and ease of use makes it a reliable alternative to other conventional methods available.
Out of a total of 311 Mycobacterium tuberculosis isolates from sputum specimens subjected to first- and second-line drug-susceptibility testing (DST) at a hospital serving as a referral center for chronic tuberculosis (TB) cases in New Delhi, 232/311 (74.6%) isolates were found to be resistant to isoniazid and rifampicin. Among multidrug-resistant (MDR) isolates, 119/232 (51.3%) were resistant to four first-line drugs (streptomycin, isoniazid, rifampicin and ethambutol). Mono-resistance to isoniazid was observed in 18 (5.7%) isolates, while none of the isolates tested showed mono-resistance to rifampicin. 50/232 (21.5%) isolates met the definition of extensively drug resistant (XDR) TB, i.e., additional resistance to a fluoroquinolone and at least one of the three injectable second-line drugs: kanamycin, capreomycin, or amikacin. Spoligotyping of the XDR-TB isolates revealed 14 patterns; 39/50 (78%) isolates being grouped in three clusters vs. 11/50 (22%) isolates being unique. SIT1/Beijing represented the largest cluster (n=21, 42%), followed by SIT26/CAS1-Delhi (n=10, 20%) and SIT 53/T1 (n=8 isolates; 16%). This study corroborates recent observations from North India suggesting that both Beijing and CAS1-Delhi lineages constitute the bulk of XDR-TB isolates that are disseminating rapidly across a large geographical region in and around the capital city of India.
The involvement of Beijing and CAS1-Delhi clades in paediatric TB patients suggests that these two lineages play a major role in ongoing active transmission.
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