LONDON: Health experts are calling for faster testing of the 9 million people worldwide estimated to be infected with tuberculosis each year after a study in China found drug-resistant strains were rife.
The study, published in the New England Journal of Medicine on Wednesday, gives the first nationwide estimate of the scale of the tuberculosis (TB) problem in China, where there are more than a million new infections every year.
It found that one in 10 Chinese patients newly diagnosed or recently treated for TB had a drug-resistant strain of the highly contagious lung disease.
Around 0.5 per cent of new cases - equating to 5,000 people a year - were diagnosed with extensively drug-resistant TB, which experts say is almost incurable.
The survey of more than 4,000 Chinese patients, conducted in 2007, follows a warning from the World Health Organisation last year that multi drug-resistant and extensively drug-resistant forms of TB are also spreading at an alarming rate in Europe.
The infection is caused by the bacterium Mycobacterium tuberculosis and destroys patients' lung tissue, causing them to cough up the bacteria, which then spreads through the air and can be inhaled by others.
Faster testing of newly diagnosed cases could improve survival rates of patients with drug-resistant forms of TB as well as slowing the development and spread of those strains.
Cases of multi drug-resistant (MDR-TB) and extensively drug-resistant TB (XDR-TB) are already spreading fast, with about 440,000 new cases a year worldwide. MDR-TB is resistant to first-line antibiotic treatments while XDR-TB is resistant to first and second-line treatments.
Experts say about 7 per cent of patients with straightforward TB die, and that death rate rises to about 50 per cent of patients with drug-resistant forms.
Upsets the Old Dogma
Richard Chaisson and Eric Nuermberger, both professors at the Johns Hopkins University School of Medicine in the United States, said the proliferation of these drug-resistant forms posed an “enormous challenge” to eradicating TB.
In a commentary on the China survey, they said among the most worrying findings was that most of the estimated 110,000 drug-resistant cases found were in people newly diagnosed with TB, suggesting drug-resistant bacteria were being transmitted from person to person.
This “upsets the old dogma”, they said, that drug-resistant TB occurred mostly in people who did not respond to first-line treatments, or in infected people who relapsed after previous drug treatment.
The experts said the study underlined the urgent need for faster testing of newly diagnosed cases to find out whether the patients had a drug resistant form of TB.
Current laboratory tests for TB, while relatively cheap at less than $5 per person, take several weeks to show bacterial growth in saliva samples.
Same-day results can be achieved with high-tech molecular tests, but they dramatically increase costs to up to $40 per person.
Treating even normal TB is a long and unpleasant process, with patients required to take a combination of powerful antibiotics for 6 months. Many patients fail to correctly complete the course of medicines, a factor which has fuelled the emergence of drug-resistance.
Treatment regimes for MDR-TB and XDR-TB can stretch to two or more years, costing up to $16,000 in drugs alone and up to $200,000 to $300,000 per patient if isolation hospital costs, medical care and other resources are taken into account.
In the same journal on Wednesday, researchers said they may have a new weapon against drug-resistant TB after trials of an experimental drug from Japanese drugmaker Otsuka found people treated with it and standard anti-TB medicines for eight weeks were more likely to see the bacteria disappear from their saliva than those who got just the standard drugs.
This result was “significant but modest”, Chaisson and Nuermberger said, and any potential new antibiotic was good news. But they said what TB doctors really needed was better information about which drug combinations worked best, when to use newer antibiotics, in what dose and order, and for how long.