R&D News: HPA scientists design new test to identify TB cases
Rapid detection of the TB bacteria (Mycobacterium tuberculosis) will ensure quick treatment for patients and could dramatically reduce the incidence and consequences of TB in the UK and worldwide if practised universally, according to HPA.
According to the scientists, the standard identification test for TB can take anything up to eight weeks to grow and identify the bacteria. Other rapid molecular tests currently available target a particular element (called IS6110) which is normally present in TB bacteria.
However, research has shown that this element is sometimes only present in very low amounts or in some cases lacking altogether in some strains of TB currently circulating. This has the effect of potentially lowering test sensitivity overall.
The scientists said that to combat this problem, HPA scientists have now developed a new ultra rapid test which substantially increases the sensitivity of the test, enabling detection of the presence of the bacteria in a sample within an hour.
The new technique is a single DNA molecule identification test which uses real-time polymerase chain reaction (PCR). PCR is a technique used in molecular biology to amplify copies of a piece of DNA and generate millions of copies of that particular DNA sequence, enabling more DNA to be tested.
In 2008 in the UK, 8,655 cases of TB were reported. The main burden of disease was concentrated in major urban areas with 39 percent of cases reported in London.
Almost three quarters of cases continue to occur in people born outside the UK (72 percent) and those aged 15-44 years (61 percent). Most of the non-UK-born patients were diagnosed two or more years after entry into the UK (77 percent).
Cath Arnold, head of the genomic services unit, at HPA said: “We're excited to have developed this new test because it means we can potentially diagnose someone at a TB clinic within an hour and start them immediately on the treatment they need. This new test could really have an impact where it is most needed.
“More than two thirds of TB infections in the UK are in non-UK born residents and other hard to reach groups concentrated in urban areas. Some of the population groups affected by tuberculosis include homeless people and transient non-UK-born patients who often travel between countries potentially disrupting treatment. This combined with the current long wait for a diagnosis can affect a patient's health outcomes and increase the risks of onward transmission of the infection.”
Trials are currently planned in laboratories across the UK being rolled out over the next year to evaluate the test further against those currently used and additional research looking at streamlining the process is also needed.
Justin McCracken, CEO of HPA, said: “Reducing the stress of waiting for test results and diagnosing a patient immediately will certainly benefit the way TB is treated in UK. This is truly pioneering research and we look forward to the results of future trials that will hopefully result in the roll out a new test that will have an impact on the incidence of the infection not only in the UK but globally.”
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