Sputum microscopy and tuberculosis
Claps and bricks
Sputum smear microscopy has been the primary method for diagnosis of pulmonary tuberculosis in low- and middle-income countries, which is where nearly 95 per cent of TB cases and 98 per cent of deaths due to TB occur.
It is a simple, rapid and inexpensive technique which is highly specific in areas with a very high prevalence of tuberculosis.
It also identifies the most infectious patients and is widely applicable in various populations with different socio-economic levels. Hence, it has been an integral part of the global strategy for TB control.
However, sputum smear microscopy has significant limitations in its performance. The sensitivity is grossly compromised when the bacterial load is less than 10,000 organisms/ml sputum sample. It also has a poor track record in extra-pulmonary tuberculosis, pediatrics tuberculosis and in patients co-infected with HIV and tuberculosis.
DNA test and TB
TB Overcoming old order microscopy-hurdles
In 1995, nucleic acid amplification tests (NAATO) ware initially approved to be performed on respiratory specimens from patients with smear-positive AFB and clinical features of tuberculosis (TB) Nucleic acid amplification test sensitivity and specificity in diagnosing MTB has been reported to be as high as 99% and 98%, respectively, resulting in a higher MTB detection rate and shorter time to treatinent Initiation. Nucleic acid amplification tests of respiratory specimens from patients with suspected pulmonary TB has been recommended by the US Centers for Disease Control and Prevention (CDC)
Searching TB by its DNA in Rural Indian villages
Affordability
While 25.01 per cent of the population is multidimensionally poor in the country, the poverty ratio is as high as 32.75 per cent in rural areas. This is against 8.81 per cent of the population in urban areas.
The pattern is the same in states and Union Territories in varying degrees – a greater proportion of the poor in villages than in urban areas except for Delhi, which is predominantly a city state.
– Indivjal Dhasmana New Delhi December 5, 2021 23:29 IST BUSINESS STANDARD
Feasibility
While seeking Tb by its DNA seems to be the ultimate form of Tb diagnostics, formidable infra cost by way of CAPEX, stable electric supply and educated manpower severely challenge their inclusion in resource limited rural India.
TB screening in rural India
The need
- DNA based detection
- Amplified DNA for sensitivity
- Rapid
- Instruments?
- Sequencer | Real Time PCR | Thermal cyoler
- Anything frugal-like, just a heating box for 30 minutes?
