Derek Thaczuk
January 05, 2007
A systematic review of studies in low- and middle-income countries has
found reports of latent TB infection among 33% to 79% of all health care
workers in these settings. Most health care facilities examined had no
specific TB control measures in place. The review is published in the
January edition of the on-line journal PLoS Medicine.
Fully one-third of the world’s population is latently infected with
Mycobacterium tuberculosis. About 10% of infected people develop
active tuberculosis (TB), a potentially fatal infection. Since TB is
very easily spread by people with active pulmonary infection, health
care workers are at great risk for contracting it. In developed,
higher-income countries, prevalence rates of latent TB infection among
health care workers range between 5% and 55%. Since the introduction of
widespread TB infection-control measures, the annual risk of infection
in these settings has dropped to between 0.1% and 1.2% (from 0.1% to 10%
in studies published before 1995).
In lower-income countries, where 90% of the world’s TB cases occur,
there is very little money for infection control. A research team from
India, Canada and the US recently conducted a systematic review of
published studies to estimate the risk of TB among health care workers
in “low- and middle-income countries” (LMICs - defined as those with a
gross national per-capita income lower than $10,066 USD in 2004) in
Africa, Asia, South and Central America. They found that the prevalence
of latent TB infection among health care workers in these countries was
reported as, on average, 54% (range 33% to 79%). Estimates of annual
risk ranged from less than 1% to 14%. Certain work locations (e.g.
emergency and TB inpatient facilities, and labs) and occupations (e.g.
nurses, radiology technicians and patient attendants) were at higher
risk.
The team calculated that “after accounting for the incidence of TB in
the relevant general population, the excess incidence of TB…
attributable to being a [health care worker] ranged from 25 to 5361
cases per 100,000 people per year.”
The researchers reached these conclusions by extracting data from 51
English-language studies, published in 42 articles, and contacting TB
experts worldwide. They acknowledge that “only studies where there was a
high incidence” may have been published, skewing the results higher, and
that the omission of non-English studies may have biased the results.
(However, English abstracts of several non-English studies showed
comparable results.)
Another major limitation was the lack of data on latent TB in these
countries at large, making it difficult to compare health care workers
to the general population. However, the review showed that TB prevalence
increased with time spent in the profession, likely reflecting
cumulative exposure, and incidence in health care workers was “generally
higher than the estimated TB rates in the general population.”
The researchers concluded that risk reduction “should be a high priority
because occupational TB leads to the loss of essential, skilled [health
care workers]”, and that “well-designed field studies are urgently
needed to evaluation whether the TB-control measures that have reduced
TB transmission … in high-income countries will work and be affordable
in LMICs.”
http://www.aidsmap.com/en/news/641D6748-3BA0-400D-A69D-8EFB0D98C15F.asp
