Introduction
Tuberculosis (TB), also known as consumption,
wasting disease and the white plague, has impacted many people over the
centuries. The disease was not discovered to be contagious until 1865.
In 1882, the tubercule bacillus was discovered to cause the disease. The
twentieth century brought pharmaceutical treatments and turned TB from a
death sentence to a treatable disease. Part I of this course addressed
vaccinations, medical evaluations and an overview of screening and
diagnosis. Part II expands beyond those to address tools for screening
and diagnosis, as well as treatment options and protective measures.
Multiple-Puncture Test
Multiple-puncture test (tine test) is done by
puncturing the skin of the forearm with a set of short prongs or tines
coated with tuberculin. Multiple-puncture tests are easy to give, and
they are convenient because they do not require a needle and syringe.
However, in the multiple-puncture test, the amount of tuberculin that
actually enters the skin cannot be measured. Because the amount of
tuberculin can always be measured during a Mantoux test, this type of
test is more accurate and is the preferred method.
Positive reactions to multiple-puncture tests
should always be confirmed with a Mantoux test (except when there is
blistering at the site of the injection).
Chest X-ray
If a person has been infected with TB, but has
not developed disease, the chest X-ray usually will be normal. Most
people with a positive PPD have normal chest X-rays and continue to be
healthy. For such people, under certain circumstances, preventive
medication is recommended. However, if the germ has attached and caused
inflammation of the lungs, an abnormal shadow is usually visible on the
chest X-rays. For these people, diagnostic tests (a sputum test) and
treatment usually are appropriate.
A posterior-anterior radiograph of the chest is
the standard view used for the detection and description of chest
abnormalities. In some instances, another view (example: lateral,
lordotic) or additional studies (CT scans) may be necessary.
In pulmonary TB, chest radiographic
abnormalities are often seen in the apical and posterior segments of the
upper lobe or in the superior segments of the lower lobe. However,
lesions may appear anywhere in the lungs and may differ in size, shape,
density and cavitation, especially in HIV-positive and other
immunosuppressed persons.
In HIV-infected persons, pulmonary TB may
present atypically on the chest X-ray. For example, TB may cause
infiltrates without cavities in any lung zone, or it may cause
mediastinal or hilar lymphadenopathy with or without accompanying
infiltrates and/or cavities. In HIV-positive persons, almost any
abnormality may indicate TB. Many hospitals adapt strict isolation
policies in patients with HIV and chest X-ray abnormalities until TB is
excluded.
Old healed tuberculosis usually presents a
different radiologic appearance from active tuberculosis. On
radiographic findings, dense pulmonary nodules, with or without visible
calcification, may be seen in the hilar area or the upper lobes. Smaller
nodules, with or without fibrotic scars, are often seen in the upper
lobes. Upper-lobe volume loss often accompanies these scars. Nodules and
fibrotic lesions of old healed tuberculosis have well demarcated, sharp
margins and are often described as “hard”. Bronchiectasis of the
upper lobes is a nonspecific finding that sometimes occurs from previous
pulmonary tuberculosis. Pleural scarring may be caused by old
tuberculosis, but is more commonly caused by trauma or other infection.
Nodules and fibrotic scars may contain slowly
multiplying tubercle bacilli with the potential for future reactivation
to active tuberculosis. The risk of reactivation is significant, and
people who have nodular or fibrotic lesions consistent with findings of
old tuberculosis on chest X-ray and have a positive tuberculin skin test
reaction should be considered high priority candidates for treatment of
latent infection regardless of age. Conversely, calcified nodular
lesions (calcified granuloma) pose a very low risk for future
progression to active tuberculosis.
Abnormalities on chest X-rays may be suggestive
of, but never diagnostic of, TB. However, chest X-rays may be used to
rule out the possibility of pulmonary TB in a person who has a positive
reaction to the tuberculin skin test and no symptoms of disease.
Diagnostic Microbiology
Samples of sputum coughed up from the lungs can
be tested for TB germs. The sputum is examined under a microscope (a “sputum
smear”) for evidence of the TB organism. The organisms are then grown
in the laboratory to identify them as TB germs and to determine what
medications are effective in treating them. These studies are referred
to as a culture and sensitivity testing. State health department
laboratories and reference laboratories can perform such testing.
Persons suspected of having pulmonary or
laryngeal TB should have at least three sputum specimens examined by
smear and culture. It is best to obtain a series of early morning
specimens collected on three consecutive days. Specimens should be
obtained in an isolated, well-ventilated area.
A healthcare worker should coach and directly
supervise the person at least the first time sputum is collected.
Persons should be properly instructed in how to produce a good specimen.
Patients should be informed that sputum is the material brought up by
the lungs and that the mucus from the nose or throat and saliva are not
good specimens.
For patients unable to cough up sputum, deep
coughing may be induced by inhalation of an aerosol of warm, hypertonic
(5 percent -15 percent) saline. Patients should be given time -— 15
minutes is usually sufficient -— to produce sputum, which brought up
by a deep cough. Because induced sputum is very watery and resembles
saliva, it should be labeled “induced” to ensure that the laboratory
staff will not discard it.
During specimen collection, patients produce an
aerosol that may be hazardous to healthcare workers or other patients in
close proximity. For this reason, precautionary measures for infection
control must be followed during sputum induction, bronchoscopy or other
common diagnostic procedures.
Laboratory Examination
Detection of acid-fast bacilli (AFB) in stained
smears examined microscopically may provide the first bacteriologic clue
of TB. Smear examination is an easy and quick procedure: results should
be available within 24 hours of collection. However, smear examination
permits only the presumptive diagnosis of TB because the AFB in the
smear may be mycobacteria other than M. tuberculosis.
Furthermore, many TB patients have negative AFB smears. Positive
cultures for M. tuberculosis confirm the diagnosis of TB;
however, TB may also be diagnosed on the basis of clinical signs and
symptoms in the absence of a positive culture. Culture examinations
should be done on all specimens, regardless of AFB smear results.
Follow-up bacteriologic examinations are
important for assessing the patient’s response to therapy. At a
minimum, specimens should be obtained at monthly intervals until the
culture results convert to negative. Culture conversion is the most
important objective measure of response to treatment. Conversion is
documented by the first negative culture in a series of cultures.
Laboratories should report positive smears and
positive cultures within 24 hours by telephone or fax to the primary
healthcare provider. It is the responsibility of the primary healthcare
provider to promptly report all suspected or confirmed cases of TB to
the health department so that a contact investigation can be initiated
as quickly as possible.
Multi-drug Resistant Tuberculosis
Multidrug resistant tuberculosis --
characterized by the presence of bacteria resistant to at least
isoniazid and rifampin -- is increasing worldwide. Because large
populations of tuberculosis microorganisms always contain some mutants
naturally resistant to medications, a substantial population of
resistant microorganisms is always selected when a single medication is
used to treat a patient with a large population of microorganisms. This
occurs because only the microorganisms susceptible to the medications
are killed, leaving the resistant microorganisms to multiply. When the
microorganisms in a patient are resistant to all but one of the
medications given to that patient, the treatment has the same result as
when a single medication is given alone. Microorganisms with resistance
to at least the two important medications, isoniazid and rifampin, are
termed “multidrug-resistant”. This renders the patient extremely
difficult to treat. Therapy may need to be prolonged for up to two years
compared with the standard regimen for tuberculosis of six months. Using
a second line is difficult and expensive, as adverse effects are often
common.
Treatment of Tuberculosis
Isoniazid and rifampin are by far the most
important; isoniazid because it kills the great bulk of bacteria,
rapidly rendering the patient non-infectious within days of starting
treatment, and rifampin because it eliminates the persisting bacteria,
allowing for the treatment time to be shortened considerably. Treatment
with these two drugs alone for nine months will provide cure in 95
percent of cases. However patients should not be started on two drugs
alone in case resistance is present to one of them. The addition of
pyrazinamide for the first two months only allows treatment to be given
for as little as six months. If ethambutol only is given for the first
two months of treatment instead of pyrazinamide, the total time of
treatment should be nine months. Because of the emergence of more drug
resistant cases worldwide, the current recommendation is to give
four-drug therapy: pyrazinamide and ethambutol in addition to isoniazid
and rifampin until culture and sensitivity results are available.
In patients who have had previous treatment, a
more complex regimen may be needed initially. It is important that the
four-drug regimen is continued until culture and sensitivity results are
available.
Practical Management
Doctors treating tuberculosis should ideally be
part of the public health system. They should have access to first-class
bacteriological services providing excellent sputum smear
identification. They must have good quality drugs and should make sure
that the patient receives the drugs under direct supervision. This is
best provided by the patient attending a local clinic three times weekly
for directly observed therapy. Rifampin should always be given in a
combination tablet with isoniazid to prevent monotherapy resulting in
the emergence of drug resistance. Meticulous care must be taken over
recordkeeping. There should be a clinic register, which is to be kept up
to date with each patient’s attendance. This must agree with the
register kept in the bacteriological laboratory. There should be a
second separate record card for each patient, which is completed as the
patient is seen taking his medication. Regular quarterly and annual
returns should be made so that district services can know the incidence
of the disease on a regular basis and provide sufficient resources for
the good management of tuberculosis within the area for which they are
responsible.
The Solution
The practical solution must concentrate on the
completed correct treatment of the great majority of those suffering
from tuberculosis, particularly those that are sputum smear positive. It
is for this reason the World Health Organization is vigorously promoting
the direct observation therapy (DOTS) campaign. Nonadherence to
tuberculosis treatment is the major problem in TB control. Inadequate
treatment can lead to relapse, continued transmission, and the
development of drug resistance.
The current management of tuberculosis in many
parts of the world is poor. There is virtually no supervision of the
patient to ensure compliance. The result is that the patient is not
completely cured of the disease and another half-treated patient burdens
the community. Doctors who cannot treat tuberculosis properly should not
treat tuberculosis.
What can nurses do in developing an infection
control plan of action?
The primary emphasis must be on infection
control. The infection control plan should have three goals:
1. The use of administrative controls to reduce
the risk of exposure to persons with infectious tuberculosis.
2. The use of engineering controls to prevent
the spread and reduce the concentration of infectious droplet nuclei in
the air.
3. The use of personal respiratory protection in
areas where there is an increased risk of exposure to <I>M.
tuberculosis<$>, such as TB isolation rooms.
Administrative Controls
The use of administrative controls is the
primary strategy for infection control. Administrative controls are
measures intended primarily to reduce the risk of exposing uninfected
persons to persons who have infectious TB.
All healthcare facilities or settings must have
guidelines for the prompt detection of suspected TB cases. These
guidelines should include assigning supervisory responsibilities for TB
control.
Engineering Controls
The second level of the hierarchy is the use of
engineering controls to prevent the spread and reduce the concentration
of infectious droplet nuclei. Engineering controls are based primarily
on the use of adequate ventilation systems; these may be supplemented
with high-efficiency particulate air (HEPA) filtration and ultraviolet
germicidal irradiation (UVGI) in high-risk areas. These strategies are
designed to reduce the concentration of infectious droplet nuclei in the
air, prevent the dissemination of droplet nuclei throughout the
facility, or render droplet nuclei non-infectious by killing the
tubercle bacilli they contain.
TB can spread by airborne droplet nuclei that
remain suspended in and can be widely dispersed by air currents over
considerable distances. Patients must be placed in a monitored negative
pressure room that provides six to 12 air exchanges per hour.
Susceptible individuals should not enter the room unless they use their
personal respiratory protection.
Personal Respiratory Protection
The third level of the hierarchy is the use of
personal protection. In some settings such as TB isolation rooms,
administrative and engineering controls may not fully protect healthcare
workers from infectious droplet nuclei. Healthcare workers should use
personal (particulate) respirators in these settings. The Occupational
Safety and Health Administration (OSHA) requires the use of certified
respirators when respiratory protection is needed. Only particulate
respirators that have been certified by the National Institute for
Occupational Safety and Health (NIOSH) should be worn for TB protection.
Some people confuse surgical masks and personal
(particulate) respirators. Surgical masks are designed to prevent the
respiratory secretions of the person wearing the mask from entering the
air. Particulate respirators are designed to filter the air before it is
inhaled by the person wearing the respirator. Patients suspected of
having or known to have TB should never wear a respirator that has an
exhalation valve, because this type of respirator does not prevent
expulsion of droplet nuclei into the air.
The general population must be mobilized to
participate, including community organization as well as groups of
healthcare professionals. It is important to make clear to the
population that tuberculosis is curable and that there is no basis for
discrimination or stigma. Treatment must be given to every patient
confirmed as having tuberculosis, and must be given free of charge to
the patient. Community participation is essential to encourage
individuals with symptoms suggestive of tuberculosis to present
themselves to health services for diagnostic examination and to ensure
that tuberculosis patients continue to take their treatment until they
are cured.
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