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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3063_Библиотеки_им_академика_М_И_Перельмана
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A positive PPD test should never be considered as a result of the Bacille Calmette-Guérin
administration. This patient is considered to have a positive PPD because of the size of the
induration of the reaction.
A PPD test is generally considered to be positive if the induration >10 mm; in an HIV-positive
patient, however, anything >5 mm is considered positive. (Other conditions which lower the
cutoff for a positive reaction to 5 mm are steroid use, organ transplantation (recipients), close
contact with those who have active TB, and chest x-ray findings consistent with old (nonactive)
TB.)
Treatment Plan
Discussion
TB is caused by Mycobacterium tuberculosis, which is spread from person to person through
the air. It usually affects the lungs (primary or pulmonary TB), but can also affect other parts of
the body, such as the brain, kidneys, and spine. Not everyone infected with TB bacteria
becomes sick. As a result, 2 TB-related conditions exist: latent TB and active TB.
The Mantoux test consists of intradermal injection of 0.1 mL of PPD in the forearm. The
injection site is evaluated in 48-72 hours after injection. The reading is based on the diameter
of the induration/swollen area (not the red area). Measure perpendicularly to the long axis of
the forearm.
Isoniazid and vitamin B6 for 9 months1.
Persons with latent TB infection have no symptoms and do not feel sick; they are infected
with M. tuberculosis but do not have active TB disease.
The only sign of TB infection is a positive reaction to the tuberculin skin test or TB blood
test.
Persons with latent TB infection are not infectious and cannot spread TB infection to others.
201
Current recommendations from the CDC as to what constitutes a positive reading take into
account the degree of clinical suspicion of latent TB infection. Never place a PPD first in
acutely symptomatic patients.
What is the “booster effect”? Some patients, especially the elderly who were infected with
TB in the distant past, may no longer react to a TB skin test (‘amnestic’). The PPD may
boost their immune system enough so that they react to subsequent skin tests. The “2-step
testing” assesses the responses to skin-test antigens to which a cell-mediated, delayed-type
hypersensitivity (DTH) response is expected.
Two interferon-gamma release assays (IGRAs) are available in the United States:
QuantiFERON
®
–TB Gold In-Tube test (QFT-GIT)
—
T-SPOT
®
TB test (T-Spot)
—
The QuantiFERON was approved by the FDA in 2005 as a means of diagnosing TB. An
alternative to skin testing. it is performed by incubating the patient’s blood for 16-24 hours
with synthetic peptides representing 2 TB specific antigens. The antigens will stimulate
interferon-gamma release from the patient’s WBCs, which is then measured by ELISA.
Results are reported as positive, negative, or indeterminate.
FDA-approved in 2008, the T-SPOT is a unique, single-visit blood test for TB screening,
also known as an interferon gamma release assay; it is the only blood test for latent TB that
has demonstrated both sensitivity and specificity exceeding 95%.
Advantages of IGRAs: patient does not need to return for a read, results are available within
24 hours, there is no booster phenomenon, and there is no reader bias. Also, the result is not
affected by prior BCG vaccination, and not affected by HIV status.
In patients presumed to have latent TB, it is essential to rule out active TB. If latent TB
treatment is given to someone with active TB, there is a serious risk of developing drug-
resistant strains of TB.
There are 4 (CDC 2014) treatment regimens:
9 months of isoniazid (gold standard; 93% effective)
—
6 months of isoniazid is also acceptable based on cost-effectiveness, patient compliance,
and drug toxicity
—
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A positive PPD skin test indicates an exposure to TB, not necessarily an active infection.
About 10% of healthy individuals who have a positive PPD test develop active TB in their
lifetime. Most cases (>90%) occur within the first 2 years after a negative test converts to a
positive test.
PPD Conversion:
>5 mm Close contacts of active TB, HIV-positive, steroid users
>10 mm Patients from endemic areas; health care workers; and those living in shelters,
long-term facilities, and jails. Also, patients with chronic diseases, e.g.,
silicosis, diabetes, alcoholics, renal failure, and cancer
>15 mm Patients with no risk factors
Final Diagnosis
Positive PPD skin test; latent TB
4 months of rifampin for those who are unable to take INH or had exposure to INH-
resistant TB
—
3 months (12 dose) regimen of weekly rifapentine and isoniazid—
In order to become infected with TB, you need consistent exposure to the contagious person
for a long time. For that reason, you’re more likely to catch TB from a relative than a
stranger.
Latent TB is assumed by most doctors today to be the normal or regular strain of TB. There
are 3 other types of TB recognized in the world today:
Multi-drug resistant tuberculosis (MDR TB)1.
Extensively drug resistant tuberculosis (XDR TB)2.
Totally drug resistant tuberculosis (TDR TB)3.
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Case 5
Chief Complaint
Fever, chills, and productive cough for 3 months
History and Physical Examination
A 39-year-old homeless man presents with a several-month history of a productive cough.
He also reported nightly fevers to 39.5 C (103.1 F) associated with chills. During the past
6 months he has had a 20-lb weight loss. He is a nonsmoker, and his medical history is
significant for a hospitalization for pneumonia 4 months ago. He was lost to follow-up
after discharge.
His T is 38.4 C (101.1 F), BP 105/60 mm Hg, pulse 88/min, and respirations 20/min. He
is thin and unkempt-appearing in no acute distress. He has bitemporal wasting, poor
dentition, and multiple 1- to 2-cm mobile cervical lymph nodes. His cardiac and
pulmonary examinations are normal. Examination of the abdomen is benign, and
extremities are normal.
Differential Diagnosis
Tuberculosis1.
Lung abscess2.
Bronchiectasis3.
Lung cancer4.
Pneumonia5.
205
Initial Management
Setting: emergency department (patient may come to the clinic initially but should be
transferred to the hospital setting promptly)
Initial Diagnostic Plan Results
Cavitary lesion in right upper lobe
Further Diagnostic Plan Results
Rare acid-fast bacilli seen
Assessment
Given the chronicity of the patient’s symptoms in association with fever, weight loss, and
hemoptysis, tuberculosis must be highly considered in the differential diagnosis. Although a
primary lung cancer may present similarly (with a cavitary lung lesion), this would be less
likely given the patient’s age and lack of smoking history.
Treatment Plan
Begin antituberculous drug therapy with 4 agents: isoniazid (INH), rifampin, pyrazinamide,
ethambutol, which are used with vitamin B6 for the first 2 months. After that, isoniazid and
rifampin are continued for 4 months, making it a 6-month total.
Further Results (Weeks Later)
Chest x-ray
Respiratory isolation and sputum for acid-
fast bacillus stain and culture
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Culture is positive for M. tuberculosis.
Discussion
TB must be suspected in patients who present with the classic findings of cough, fever, and
weight loss in association with an infiltrate on chest x-ray. When there is clinical suspicion for
TB, respiratory isolation must be promptly instituted regardless of whether an initial sputum
smear reveals acid-fast bacilli.
All cases of TB must be reported to the Department of Health as a measure of infection control.
Given the recent emergence of multi-drug-resistant strains, the current recommendation is to
begin therapy with 4 drugs until the specific drug sensitivities become available. Directly
observed therapy programs (DOT), available in most inner cities, have improved the
compliance rates with multiple drug regimens.
The purified protein derivative (PPD) skin test was not used in this case because it is used as a
screen of asymptomatic patients. The PPD is not used to make a diagnosis of TB in acutely ill
patients such as are described here.
For most patients, the duration of therapy is 6 months total.
Epidemiology
TB is still a leading cause of death in the world. The World Health Organization (WHO)
estimates that about 1/3 of the world’s population is infected. The global incidence of active
TB is increasing, mainly due to TB associated with HIV infection.
Sites of TB disease
Lungs (80–85%)—
Pleura—
Central nervous system—
207
Lymphatic system
—
Genitourinary system
—
Bones and joints
—
Peritoneum
—
Terminology for TB
Ghon focus is a primary lesion usually subpleural caused by TB.
—
If the Ghon focus also involves infection of adjacent lymphatics and hilar lymph nodes, it
is known as the Ghon’s complex.
—
When a Ghon’s complex undergoes fibrosis and calcification, it is called a Ranke
complex.
—
The lungs are the major site for M. tuberculosis infection. Clinical manifestations of
pulmonary TB include:
Primary TB
—
Reactivation TB
—
Laryngeal TB
—
Endobronchial TB
—
Pulmonary complications of TB include:
Hemoptysis
—
Pneumothorax
—
Bronchiectasis
—
Extensive pulmonary destruction
—
Lung cancer
—
Chronic pulmonary aspergillosis
—
Manifestations of active TB:
Fever
—
Night sweats
—
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Weight loss—
Chronic cough (>3 weeks)—
Hemoptysis—
Local signs/symptoms for extrapulmonary disease—
Suspect the diagnosis of active TB in:
High-risk group—
Worrisome chest x-ray—
Consistent symptoms—
Isolate early
Airborne precautions—
Negative pressure ventilation room—
Use an N-95 respirator—
Diagnosis for active TB
Chest x-ray / CT chest—
Infiltrates typically upper lobe or superior segments of lower lobes—
Sputum for AFB stain and culture × 3—
Note: CXR can be normal in HIV (+) patients—
Diagnosis of extrapulmonary TB
Pleural—
Pleural fluid stain/culture
Adenosine deaminase
Mycobacterium tuberculosis PCR
QuantiFERON Gold on the fluid
Pleural biopsy (gold standard)
Meningitis
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Final Diagnosis
Active TB
CSF stain/culture
—
Meningeal biopsy
—
The first successful treatments for TB were surgical. They were based on the observation
that healed TB cavities were all closed. Surgical management was therefore directed at
closing open cavities in order to encourage healing. These procedures were all used in the
pre-antibiotic era.
There also exists a misconception that the purpose was to deprive the organism of oxygen;
however, it is well known that TB survives anaerobic conditions. Plombage involved
inserting porcelain balls into the thoracic cavity to collapse the lung underneath and thus
reduced the need for a disfiguring operation.
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