"If a minister can do it, it can’t be that hard," said South African Health Minister Aaron Motsoaledi, demonstrating the new GeneXpert test for TB (photo: Lettie Ferreira).
One of the most striking actions announced by Minister Motsoaledi during last week's launch of South Africa's new direction on TB control
was the roll out of the GeneXpert
MDR/RIF test for TB to become the
first-line test to diagnose active TB throughout South Africa.
TB diagnosis system automates sample processing on sputum providing real time
PCR results. It promises to revolutionise the field by diagnosing both TB and
rifampicin-resistance in under two hours (even in most smear-negative cases) —
potentially a ‘while you wait’ test, so that a person could be tested,
diagnosed and started on treatment on the same day.
In addition, since the test also detects the presence of
rifampicin resistance, which generally indicates MDR-TB, people who present to
care with MDR-TB could receive a diagnosis and be put onto effective treatment
months earlier than under the current protocols.
Another major selling point is that the GeneXpert doesn’t
require a sophisticated laboratory set-up or a highly trained lab technician to
run this test — nurses or other staff could be trained to perform the test. In
fact, at the start of the day, the Minister himself demonstrated performance of
the test in front of the media, noting that 54 people had been trained in the
previous two weeks to perform the GeneXpert test in South Africa — 55 including
“If a minister can do it, it can’t be that hard,” he said,
smiling for the cameras.
Perhaps even more striking, the test the Minister ran was
not performed on the small desktop unit that has been piloted at several sites
in South Africa.
Instead, Prince Mshiyeni Hospital
has been outfitted with the new ‘Infinity G-48’ machine, which performs 48
tests at a time, or approaching 200 on an 8-hour shift. This machine, which
costs 2.8 million Rand (over US $400,000) is the only such machine in Africa,
and one of only five such machines outside of the United States. Meanwhile, one G-16
machine (at 600,000 Rand each) has been placed in each of South Africa’s
9 provinces, and 20 G-4’s (which cost around 120,000 Rand each) have been
placed in various sites across the country.
“Over the next 18 months, we will roll this out to the
length and breadth of the whole country; we will put them in the national
health laboratory services facilities,” said the Minister.
However, whether a country with such a huge burden of TB can
truly scale up the capacity to switch TB diagnosis entirely over to GeneXpert
systems in such a short time remains to be seen, and what it will actually cost
is anyone’s guess. In addition to the equipment cost, the cost of each TB test
is approximately $16 per test (for the reagent, not including the operator
time). At present, South
Africa performs about 4.6 million smear
microscopy tests to diagnose somewhere over 400,000 TB cases each year.
Accordingly, the Treatment Action Campaign continued to call for price
reductions from the manufacturer in its World TB Day statement.
Presumably, fewer GeneXpert tests will be required than the
two or three smears needed to diagnose TB because of their higher sensitivity —
only one test would be required for each person being tested for TB, unless
smear-negative TB is suspected.
According to Romain Prieur, Senior Manager for Tuberculosis
at Cepheid, the company that makes GeneXpert, the test is only 75% sensitive in
people with smear-negative TB, a second test increases sensitivity by about
10%, a third test, by another 5%.
Although the Department of Health (DOH) only plans one test
per person, a second test may be warranted to reach 85% sensitivity in
populations at greater risk of smear negative TB — such as people with HIV or
children. But such operational issues are sure to be worked out as GeneXpert is
increasingly used in clinical practice.
See the following linked reports for further information: