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Causes
Tuberculosis is caused by bacteria that spread from person to person through microscopic droplets released into the air. This can happen when someone with the untreated, active form of tuberculosis coughs, speaks, sneezes, spits, laughs or sings.[7] The Mycobacterium tuberculosis bacterium causes TB.[8] This rod-shaped bacterium, also called Koch's bacillus, was discovered by Dr. Robert Koch in 1882.
Characteristics
Tuberculosis is caused by bacteria that spread from person to person through microscopic droplets released into the air. This can happen when someone with the untreated, active form of tuberculosis coughs, speaks, sneezes, spits, laughs or sings.[7] The Mycobacterium tuberculosis bacterium causes TB.[8] This rod-shaped bacterium, also called Koch's bacillus, was discovered by Dr. Robert Koch in 1882.
Characteristics
- Mtb is a small, slow-growing bacterium that can live only in people. It is not found in other animals, insects, soil, or other nonliving things.
- Mtb is an aerobic bacterium, meaning it needs oxygen to survive. For this reason, during active TB disease, Mtb complexes are always found in the upper air sacs of the lungs
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TB Infection
When a person breathes in Mtb-contaminated air, the inhaled TB bacteria reach the lungs. This causes an Mtb infection. However, not everyone infected with TB bacteria becomes sick. The bacteria can remain dormant (asleep) for years and not cause any TB disease. This is called latent TB infection. People who have latent TB infection do not get sick and do not spread the bacteria to others. But, some people with latent TB infection eventually do get TB disease.
So it is important to get the appropriate treatment and get rid of the bacteria even in latent TB infection.
TB Disease
For someone to develop active TB disease, the following two events must take place:
The bacteria enter the body and cause an Mtb infection.
The immune system cannot stop the TB bacteria from growing and spreading after the initial infection.
The active bacteria multiply and destroy the tissue. A person with TB disease shows symptoms that vary, depending on where the TB bacteria are growing. In most cases, the bacteria attack the lungs.[9]
Approximately one third of the world's population is infected with Mycobacterium tuberculosis, the causative agent of tuberculosis. This bacterium has an unusual lipid-rich cell wall containing a vast repertoire of antigens, providing a hydrophobic impermeable barrier against chemical drugs.[10]
HOW TB IS SPREAD AND A PERSON IS INFECTED
TB can only be caught directly from someone with infectious TB in their lungs or throat. Although TB is spread through the air when people who have the disease cough or sneeze, it takes close and lengthy contact with an infectious person to catch the disease. So it’s unlikely that you’ll catch TB on public transport, for example. Not everyone with TB of the lungs is infectious, and as long as they are taking the proper treatment most people that were infectious become noninfectious quickly – generally after about two weeks – as long as they are taking the proper treatment. While anyone can catch TB, some groups of people are more at risk than others. These include people who:
• have lived in the same household or been in prolonged close contact with someone with infectious TB
• are living in unhealthy or overcrowded conditions, including those who are homeless or sleeping rough
• have lived, worked or stayed for a long time in an area with a high rate of TB, e.g. southeast Asia, sub Saharan Africa and some countries in eastern Europe
• may have been exposed to TB in their youth when the disease was more common in this country
• are the children of parents whose country of origin has a high rate of TB
• have been in prison
• are unable to fight off infection (immunosuppressed) due to illness (e.g. HIV infection) or treatment
• are dependent on drugs or misuse alcohol
• do not eat enough to stay healthy. [12]
Symptoms
When a person breathes in Mtb-contaminated air, the inhaled TB bacteria reach the lungs. This causes an Mtb infection. However, not everyone infected with TB bacteria becomes sick. The bacteria can remain dormant (asleep) for years and not cause any TB disease. This is called latent TB infection. People who have latent TB infection do not get sick and do not spread the bacteria to others. But, some people with latent TB infection eventually do get TB disease.
So it is important to get the appropriate treatment and get rid of the bacteria even in latent TB infection.
TB Disease
For someone to develop active TB disease, the following two events must take place:
The bacteria enter the body and cause an Mtb infection.
The immune system cannot stop the TB bacteria from growing and spreading after the initial infection.
The active bacteria multiply and destroy the tissue. A person with TB disease shows symptoms that vary, depending on where the TB bacteria are growing. In most cases, the bacteria attack the lungs.[9]
Approximately one third of the world's population is infected with Mycobacterium tuberculosis, the causative agent of tuberculosis. This bacterium has an unusual lipid-rich cell wall containing a vast repertoire of antigens, providing a hydrophobic impermeable barrier against chemical drugs.[10]
HOW TB IS SPREAD AND A PERSON IS INFECTED
TB can only be caught directly from someone with infectious TB in their lungs or throat. Although TB is spread through the air when people who have the disease cough or sneeze, it takes close and lengthy contact with an infectious person to catch the disease. So it’s unlikely that you’ll catch TB on public transport, for example. Not everyone with TB of the lungs is infectious, and as long as they are taking the proper treatment most people that were infectious become noninfectious quickly – generally after about two weeks – as long as they are taking the proper treatment. While anyone can catch TB, some groups of people are more at risk than others. These include people who:
• have lived in the same household or been in prolonged close contact with someone with infectious TB
• are living in unhealthy or overcrowded conditions, including those who are homeless or sleeping rough
• have lived, worked or stayed for a long time in an area with a high rate of TB, e.g. southeast Asia, sub Saharan Africa and some countries in eastern Europe
• may have been exposed to TB in their youth when the disease was more common in this country
• are the children of parents whose country of origin has a high rate of TB
• have been in prison
• are unable to fight off infection (immunosuppressed) due to illness (e.g. HIV infection) or treatment
• are dependent on drugs or misuse alcohol
• do not eat enough to stay healthy. [12]
Symptoms
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Although your body may harbor the bacteria that cause tuberculosis, your immune system usually can prevent you from becoming sick. For this reason, doctors make a distinction between:
Latent TB. In this condition, you have a TB infection, but the bacteria remain in your body in an inactive state and cause no symptoms. Latent TB, also called inactive TB or TB infection, isn't contagious. It can turn into active TB, so treatment is important for the person with latent TB and to help control the spread of TB in general. An estimated 2 billion people have latent TB.
Active TB. This condition makes you sick and can spread to others. It can occur in the first few weeks after infection with the TB bacteria, or it might occur years later.[11]
TB diagnosis depends on symptom screening of all patients (including HIV positive patients) presenting
to the health facility and contacts of people with laboratory confirmed pulmonary TB disease. All those
who have symptoms of TB disease must be investigated for TB.
Pulmonary TB
Latent TB. In this condition, you have a TB infection, but the bacteria remain in your body in an inactive state and cause no symptoms. Latent TB, also called inactive TB or TB infection, isn't contagious. It can turn into active TB, so treatment is important for the person with latent TB and to help control the spread of TB in general. An estimated 2 billion people have latent TB.
Active TB. This condition makes you sick and can spread to others. It can occur in the first few weeks after infection with the TB bacteria, or it might occur years later.[11]
TB diagnosis depends on symptom screening of all patients (including HIV positive patients) presenting
to the health facility and contacts of people with laboratory confirmed pulmonary TB disease. All those
who have symptoms of TB disease must be investigated for TB.
Pulmonary TB
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1) Symptoms
The main symptoms of pulmonary tuberculosis are:
• Persistent coughof 2 weeks or more or any duration if HIV positive
• Fever for more than 2 weeks
• Drenching night sweats
• Unexplained weight loss (more than 1.5 kg in a month)
A productive cough, often accompanied by systemic symptoms such as fever, night sweats or loss of weight, is the commonest presentation of pulmonary tuberculosis. Every patient with a positive symptom screen must be investigated appropriately. Not all those with TB will have a cough; therefore, a high index of suspicion is required, particularly in people who are HIV positive who may only have one of the above symptoms.
A history of contact with a person with PTB increases the likelihood of a TB diagnosis and symptoms such as weight loss need to be investigated.Some patients may present with chest pains (due to pleurisy, muscle strain), breathlessness (due to extensive lung disease or concomitant pleural effusion), localised wheeze due to local tuberculous bronchitis, or because of external pressure on the bronchus by an enlarged lymph node.
2) Physical signs
Physical signs may not be helpful in confirming the diagnosis, but it is important to examine the patient carefully. Some of the common signs are;
Fever – the body temperature may be high or irregular (greater than 38.5 degrees Celsius)
Pulse – the pulse rate may be raised because of fever
Chest – there may be no abnormal signs, crackles in the lung apices more pronounced on deep breathing; localised wheeze in local obstruction or pressure; dullness where there is effusion and in chronic disease there may be extensive fibrosis with the trachea pulled to one side.
All individuals suspected of having pulmonary tuberculosis should have at least one sputum specimen examined for bacteriological confirmation of TB disease using the rapid diagnostic tests.
Extra-pulmonary TB
The main symptoms of pulmonary tuberculosis are:
• Persistent coughof 2 weeks or more or any duration if HIV positive
• Fever for more than 2 weeks
• Drenching night sweats
• Unexplained weight loss (more than 1.5 kg in a month)
A productive cough, often accompanied by systemic symptoms such as fever, night sweats or loss of weight, is the commonest presentation of pulmonary tuberculosis. Every patient with a positive symptom screen must be investigated appropriately. Not all those with TB will have a cough; therefore, a high index of suspicion is required, particularly in people who are HIV positive who may only have one of the above symptoms.
A history of contact with a person with PTB increases the likelihood of a TB diagnosis and symptoms such as weight loss need to be investigated.Some patients may present with chest pains (due to pleurisy, muscle strain), breathlessness (due to extensive lung disease or concomitant pleural effusion), localised wheeze due to local tuberculous bronchitis, or because of external pressure on the bronchus by an enlarged lymph node.
2) Physical signs
Physical signs may not be helpful in confirming the diagnosis, but it is important to examine the patient carefully. Some of the common signs are;
Fever – the body temperature may be high or irregular (greater than 38.5 degrees Celsius)
Pulse – the pulse rate may be raised because of fever
Chest – there may be no abnormal signs, crackles in the lung apices more pronounced on deep breathing; localised wheeze in local obstruction or pressure; dullness where there is effusion and in chronic disease there may be extensive fibrosis with the trachea pulled to one side.
All individuals suspected of having pulmonary tuberculosis should have at least one sputum specimen examined for bacteriological confirmation of TB disease using the rapid diagnostic tests.
Extra-pulmonary TB
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Extra-pulmonary TB can present with non-specific symptoms such as unintentional weight loss (more
than 1.5 kg in a month), night sweats and fever for more than 2 weeks. Other symptoms depend on the site or organ affected. The most common types of extra-pulmonary tuberculosis are:
• TB lymphadenitis
• Tuberculous pleural effusion (usually single-sided)
• TB of the bones and joints
• Tuberculous pericardial effusion
• TB meningitis
• Disseminated / miliary tuberculosis
• Tuberculous empyema
• TB peritoneal effusion
Disseminated tuberculosis and tuberculosis meningitis are acute, severe forms of TB, often occurring soon after primary infection. They occur most commonly in children and young adults. These acute forms of TB are often fatal. When this form of disease is suspected, treatment should be commenced immediately without waiting for bacteriological proof of diagnosis. HIV positive patients particularly those with low CD4 counts may present with extra pulmonary disease. The presentation of extrapulmonary
TB is generally no different between HIV positive and HIV-negative patients, however,
differences do occur.
Appropriate investigations for extra-pulmonary TB include the following where these are available (usually only secondary or tertiary hospitals)
• Ultrasound examination may be suggestive of abdominal TB (lymphadenopathy, ascites and/or splenic hypodensities) or pericardial TB (pericardial effusion especially if there is stranding)
• TB blood culture
• Culture of tissue or fluid from fine needle aspirate or biopsy
• Histological examination of tissue
• Cytological examination[13]
DIAGNOSIS
Tests and diagnosis
During the physical exam, your doctor will check your lymph nodes for swelling and use a stethoscope to listen carefully to the sounds your lungs make while you breathe.
The most commonly used diagnostic tool for tuberculosis is a simple skin test, though blood tests are becoming more commonplace. A small amount of a substance called PPD tuberculin is injected just below the skin of your inside forearm. You should feel only a slight needle prick.
Within 48 to 72 hours, a health care professional will check your arm for swelling at the injection site. A hard, raised red bump means you're likely to have TB infection. The size of the bump determines whether the test results are significant. [14]
The tuberculin skin test
than 1.5 kg in a month), night sweats and fever for more than 2 weeks. Other symptoms depend on the site or organ affected. The most common types of extra-pulmonary tuberculosis are:
• TB lymphadenitis
• Tuberculous pleural effusion (usually single-sided)
• TB of the bones and joints
• Tuberculous pericardial effusion
• TB meningitis
• Disseminated / miliary tuberculosis
• Tuberculous empyema
• TB peritoneal effusion
Disseminated tuberculosis and tuberculosis meningitis are acute, severe forms of TB, often occurring soon after primary infection. They occur most commonly in children and young adults. These acute forms of TB are often fatal. When this form of disease is suspected, treatment should be commenced immediately without waiting for bacteriological proof of diagnosis. HIV positive patients particularly those with low CD4 counts may present with extra pulmonary disease. The presentation of extrapulmonary
TB is generally no different between HIV positive and HIV-negative patients, however,
differences do occur.
Appropriate investigations for extra-pulmonary TB include the following where these are available (usually only secondary or tertiary hospitals)
• Ultrasound examination may be suggestive of abdominal TB (lymphadenopathy, ascites and/or splenic hypodensities) or pericardial TB (pericardial effusion especially if there is stranding)
• TB blood culture
• Culture of tissue or fluid from fine needle aspirate or biopsy
• Histological examination of tissue
• Cytological examination[13]
DIAGNOSIS
Tests and diagnosis
During the physical exam, your doctor will check your lymph nodes for swelling and use a stethoscope to listen carefully to the sounds your lungs make while you breathe.
The most commonly used diagnostic tool for tuberculosis is a simple skin test, though blood tests are becoming more commonplace. A small amount of a substance called PPD tuberculin is injected just below the skin of your inside forearm. You should feel only a slight needle prick.
Within 48 to 72 hours, a health care professional will check your arm for swelling at the injection site. A hard, raised red bump means you're likely to have TB infection. The size of the bump determines whether the test results are significant. [14]
The tuberculin skin test
Tuberculin, a broth culture filtrate of tubercle bacilli, was first described in detail by Robert Koch in 1891, a year after he introduced it as a potential cure for tuberculosis. Although its purported curative properties proved unfounded, Koch observed that subcutaneous inoculation of tuberculin led to a characteristic febrile reaction in patients who had tuberculosis but not in those who did not have tuberculosis, giving rise to its use in the diagnosis of the disease. The technique was refined over the next 2 decades so that cutaneous or intradermal inoculation restricted the reaction to the skin. Subsequently, a standardized version of tuberculin, the
purified protein derivative (PPD), was introduced in 1934. In 1939, the batch of PPD known as PPD-S was produced by Seibert and Glenn. This batch remains the international standard for PPD to this day. [15]
Results can be wrong
The TB skin test isn't perfect. Sometimes, it suggests that people have TB when they really don't. It can also indicate that people don't have TB when they really do.
A false-positive test may happen if you've been vaccinated recently with the bacille Calmette-Guerin (BCG) vaccine. This tuberculosis vaccine is seldom used in the United States but is widely used in countries with high TB infection rates.
False-negative results may occur in certain populations — including children, older people and people with AIDS — who sometimes don't respond to the TB skin test. A false-negative result can also occur in people who've recently been infected with TB, but whose immune systems haven't yet reacted to the bacteria. [14]
purified protein derivative (PPD), was introduced in 1934. In 1939, the batch of PPD known as PPD-S was produced by Seibert and Glenn. This batch remains the international standard for PPD to this day. [15]
Results can be wrong
The TB skin test isn't perfect. Sometimes, it suggests that people have TB when they really don't. It can also indicate that people don't have TB when they really do.
A false-positive test may happen if you've been vaccinated recently with the bacille Calmette-Guerin (BCG) vaccine. This tuberculosis vaccine is seldom used in the United States but is widely used in countries with high TB infection rates.
False-negative results may occur in certain populations — including children, older people and people with AIDS — who sometimes don't respond to the TB skin test. A false-negative result can also occur in people who've recently been infected with TB, but whose immune systems haven't yet reacted to the bacteria. [14]
Blood tests may be used to confirm or rule out latent or active tuberculosis. These tests use sophisticated technology to measure your immune system's reaction to TB bacteria. QuantiFERON-TB Gold in-Tube test and T-Spot.TB test are two examples of TB blood tests.
These tests require only one office visit. A blood test may be useful if you're at high risk of TB infection, but have a negative response to the skin test, or if you've recently received the BCG vaccine.[14]
Peripheral venous blood samples are collected in tubes containing ethylenediamine tetra acetic acid (EDTA). Hematological tests are carried out using commercially available kits and done in the lab of HEOM using routine laboratory process.
The IGRA used is a whole blood assay, the QuantiFERON-TB Gold In-Tube kit (QuantiFERON-TB Gold In-Tube, Cellestis Ltd., Carnegie, Australia), performed according to the manufacturer’s recommendations. Cells are cultured in vitro with specific antigens: ESAT-6, CFP-10, and TB7.7. Samples are then incubated for 16–24 hours, centrifuged, and its supernatant were collected and stored in −80°C until use. IFN-γ levels in culture supernatants are assessed by ELISA. A positive test is defined as IFN-γblood concentration ≥0.35 international units (IUs)/mL [16]
These tests require only one office visit. A blood test may be useful if you're at high risk of TB infection, but have a negative response to the skin test, or if you've recently received the BCG vaccine.[14]
Peripheral venous blood samples are collected in tubes containing ethylenediamine tetra acetic acid (EDTA). Hematological tests are carried out using commercially available kits and done in the lab of HEOM using routine laboratory process.
The IGRA used is a whole blood assay, the QuantiFERON-TB Gold In-Tube kit (QuantiFERON-TB Gold In-Tube, Cellestis Ltd., Carnegie, Australia), performed according to the manufacturer’s recommendations. Cells are cultured in vitro with specific antigens: ESAT-6, CFP-10, and TB7.7. Samples are then incubated for 16–24 hours, centrifuged, and its supernatant were collected and stored in −80°C until use. IFN-γ levels in culture supernatants are assessed by ELISA. A positive test is defined as IFN-γblood concentration ≥0.35 international units (IUs)/mL [16]
![Picture](/uploads/4/8/0/7/48079199/7754505.jpg?295)
Imaging tests
If you've had a positive skin test, your doctor is likely to order a chest X-ray or a CT scan. This may show white spots in your lungs where your immune system has walled off TB bacteria, or it may reveal changes in your lungs caused by active tuberculosis. CT scans provide more-detailed images than do X-rays. [14]
If you've had a positive skin test, your doctor is likely to order a chest X-ray or a CT scan. This may show white spots in your lungs where your immune system has walled off TB bacteria, or it may reveal changes in your lungs caused by active tuberculosis. CT scans provide more-detailed images than do X-rays. [14]
![Picture](/uploads/4/8/0/7/48079199/3693322.jpg?250)
Sputum tests
If your chest X-ray shows signs of tuberculosis, your doctor may take samples of your sputum — the mucus that comes up when you cough. The samples are tested for TB bacteria.
Sputum samples can also be used to test for drug-resistant strains of TB. This helps your doctor choose the medications that are most likely to work. These tests can take four to eight weeks to be completed.
Sputum-based diagnosis
To establish a diagnosis of pulmonary tuberculosis, respiratory samples are submitted to the laboratory for microscopy (AFB smear) and for mycobacterial culture. NAA assays may also be used in the diagnostic algorithm. The technique used to obtain the respiratory sample strongly influences the ability to detect pulmonary tuberculosis. Expectorated sputum is generally the starting point. Three samples are collected on
three separate days and stained for AFB.Although, the utility of collecting three samples has been questioned the overall yield for smear and culture is superior to collecting fewer specimens . Samples are generally sent simultaneously for smear and culture, because culture data are essential for confirmation of the diagnosis. In resource poor
countries, the cost of culture is often too great, resulting in reliance solely on AFB smears.
The sensitivity of sputum AFB smears for detecting pulmonary tuberculosis is limited by the need for 5000 to 10,000 bacilli per milliliter to be present
in a specimen to allow detection. The sensitivity of expectorated sputum ranges from 34% to 80%; the sensitivity tends to be highest in patients who have cavitary disease and lowest in patients who have weak cough or less advanced disease. In no way does a negative sputum smear eliminate the diagnosis of active tuberculosis, particularly if the clinical suspicion is high. Instituting therapy in such cases often is warranted while awaiting culture results. If a patient is suspected of having pulmonary tuberculosis but is smear negative on expectorated sputum or is unable to produce sputum form testing (30% of patients in one series ,further diagnostic testing may be warranted. The optionsinclude sputum induction (SI), fiberoptic bronchoscopy (FOB), and perhaps gastric washings (GW). The following discussion refers specifically to patients who are expectorated sputum smear negative or who cannot produce an expectorated sputum sample.
Sputum induction
SI in the diagnosis of active disease was first described in 1961 by Hensler and colleagues They adapted an earlier technique used to obtainsputum for cytology in diagnosing lung cancer. Early studies compared SI with the well-established method of gastric aspiration]. In patients unable to expectorate or who had smear-negative sputum samples, SI was superior to GW in obtaining a suitable sample for culture, although the two techniques were noted to be complementary.GW probably adds to overall diagnosis, and, according to one author, its value has been underestimated in recent years . The role of GW in adults is probably quite limited, however. SI, on the other hand, has proven effective in patients clinically suspected of having pulmonary tuberculosis who are either unable to produce sputum or are sputum smear negative. SI has performed well in resource-poor countries with little added cost. In South Africa, SI performed on 51 patients yielded a suitable sample in 36. Fifteen of the 36 patients (42%) were smear positive, 12 of whom were ultimately culture positive as well. In Malawi, Parry and colleagues were able to obtain SI specimens in 73 of 82 patients. Eighteen of the 73 (25%) were smear positive, and 30 of 73 (42%) were culture positive. Similarly, of 1648 patients in China, 558 (34%) were smear positive on SI samples. The direct cost per SI in that study was 37 cents In these studies, SI provided early diagnostic yield significantly. SI also seems to be cost-effective in the resource-poor setting. the diagnosis of tuberculosis 255.
Conversely, in a retrospective review of 114 patients who had culture-positive M. tuberculosis infection at an urban hospital in New York, SI added little to overall diagnosis and was deemed costly by the investigators. In 1 year, they performed 1566 SIs yielding only 16 positive smears in 10 patients. At a cost of $28.65 per SI, the annual cost of $45,000 would indeed be difficult to justify. A study in the United Kingdom confirmed a low yield but suggested there might be a role for SI. Is there a role for SI in resource-rich countries? A large, prospective study from Montreal, Canada, assessed 500 patients who were either smear negative (5%) or could not produce sputum (95%) with repeated SI. An adequate sample was obtained in 99.8% of patients. The cumulative yield of SI for smear-positive samples with successive attempts was 64%, 81%, 91%, and, after four inductions, 98%. The culture yield also increased with each attempt from 70% to 91% to 99% to 100%. This study suggests that the use of repeated SI has a high yield in this setting and that repeated SI should be considered seriously in this subset of patients [15]
If your chest X-ray shows signs of tuberculosis, your doctor may take samples of your sputum — the mucus that comes up when you cough. The samples are tested for TB bacteria.
Sputum samples can also be used to test for drug-resistant strains of TB. This helps your doctor choose the medications that are most likely to work. These tests can take four to eight weeks to be completed.
Sputum-based diagnosis
To establish a diagnosis of pulmonary tuberculosis, respiratory samples are submitted to the laboratory for microscopy (AFB smear) and for mycobacterial culture. NAA assays may also be used in the diagnostic algorithm. The technique used to obtain the respiratory sample strongly influences the ability to detect pulmonary tuberculosis. Expectorated sputum is generally the starting point. Three samples are collected on
three separate days and stained for AFB.Although, the utility of collecting three samples has been questioned the overall yield for smear and culture is superior to collecting fewer specimens . Samples are generally sent simultaneously for smear and culture, because culture data are essential for confirmation of the diagnosis. In resource poor
countries, the cost of culture is often too great, resulting in reliance solely on AFB smears.
The sensitivity of sputum AFB smears for detecting pulmonary tuberculosis is limited by the need for 5000 to 10,000 bacilli per milliliter to be present
in a specimen to allow detection. The sensitivity of expectorated sputum ranges from 34% to 80%; the sensitivity tends to be highest in patients who have cavitary disease and lowest in patients who have weak cough or less advanced disease. In no way does a negative sputum smear eliminate the diagnosis of active tuberculosis, particularly if the clinical suspicion is high. Instituting therapy in such cases often is warranted while awaiting culture results. If a patient is suspected of having pulmonary tuberculosis but is smear negative on expectorated sputum or is unable to produce sputum form testing (30% of patients in one series ,further diagnostic testing may be warranted. The optionsinclude sputum induction (SI), fiberoptic bronchoscopy (FOB), and perhaps gastric washings (GW). The following discussion refers specifically to patients who are expectorated sputum smear negative or who cannot produce an expectorated sputum sample.
Sputum induction
SI in the diagnosis of active disease was first described in 1961 by Hensler and colleagues They adapted an earlier technique used to obtainsputum for cytology in diagnosing lung cancer. Early studies compared SI with the well-established method of gastric aspiration]. In patients unable to expectorate or who had smear-negative sputum samples, SI was superior to GW in obtaining a suitable sample for culture, although the two techniques were noted to be complementary.GW probably adds to overall diagnosis, and, according to one author, its value has been underestimated in recent years . The role of GW in adults is probably quite limited, however. SI, on the other hand, has proven effective in patients clinically suspected of having pulmonary tuberculosis who are either unable to produce sputum or are sputum smear negative. SI has performed well in resource-poor countries with little added cost. In South Africa, SI performed on 51 patients yielded a suitable sample in 36. Fifteen of the 36 patients (42%) were smear positive, 12 of whom were ultimately culture positive as well. In Malawi, Parry and colleagues were able to obtain SI specimens in 73 of 82 patients. Eighteen of the 73 (25%) were smear positive, and 30 of 73 (42%) were culture positive. Similarly, of 1648 patients in China, 558 (34%) were smear positive on SI samples. The direct cost per SI in that study was 37 cents In these studies, SI provided early diagnostic yield significantly. SI also seems to be cost-effective in the resource-poor setting. the diagnosis of tuberculosis 255.
Conversely, in a retrospective review of 114 patients who had culture-positive M. tuberculosis infection at an urban hospital in New York, SI added little to overall diagnosis and was deemed costly by the investigators. In 1 year, they performed 1566 SIs yielding only 16 positive smears in 10 patients. At a cost of $28.65 per SI, the annual cost of $45,000 would indeed be difficult to justify. A study in the United Kingdom confirmed a low yield but suggested there might be a role for SI. Is there a role for SI in resource-rich countries? A large, prospective study from Montreal, Canada, assessed 500 patients who were either smear negative (5%) or could not produce sputum (95%) with repeated SI. An adequate sample was obtained in 99.8% of patients. The cumulative yield of SI for smear-positive samples with successive attempts was 64%, 81%, 91%, and, after four inductions, 98%. The culture yield also increased with each attempt from 70% to 91% to 99% to 100%. This study suggests that the use of repeated SI has a high yield in this setting and that repeated SI should be considered seriously in this subset of patients [15]
![Picture](/uploads/4/8/0/7/48079199/9742461.jpg?250)
Treatment
The WHO advises supervised treatment, (e.g. directly observed treatment (DOT)), to ensure treatment adherence and completion. The current treatment regimen for new cases of pulmonary TB consists of a three to six month treatment regimen with four different drugs which are
with daily or three times weekly dosing under DOT. These different medicines may be combined into single Fixed Dose Combination (FDC) tablets to reduce pill burden. The treatment success rate for drug-sensitive patients with this regimen is high.
Patients with previously treated TB have a high chance of a drug-resistant strain of TB and require a different approach depending on the availability of drug-sensitivity testing (DST). Where DST is routinely available, a new treatment regimen should be commenced according to the results. In situations where DST is not routinely available, patients are treated empirically with an eight month retreatment regimen containing five first-line drugs or an MDR-TB regimen including second-line drugs. The MDR-TB regimen can last from 18 months to up to 30 months and contains at least four different drugs including the use of at least one injectable medicine but has a relatively low success rate Several of the first-line or second-line TB treatments can cause liver damage and show drug-drug interactions with HIV therapy (antiretroviral drugs, ARVs). In addition these regimens have a high pill burden and require commitment from the patient and care providers.
The current treatment for LTBI recommended by WHO consists of a six month treatment with daily or three-weekly intake of four different drugs (isoniazid, rifampicin, pyrazinamide, and ethambutol).3 The United States Centers for Disease Control (CDC) and the United Kingdom National Institute for Health and Clinical Excellence (NICE) have recently approved a three month once-weekly regimen of isoniazid plus rifapentin (CDC) or rifampicin (NICE). However, this novel treatment is not suitable for young children, pregnant women, and HIV-positive patients on ARVs.[18]
A number of new drugs are being looked at as add-on therapy to the current drug-resistant combination treatment including:
Completing treatment is essential
After a few weeks, you won't be contagious and you may start to feel better. It might be tempting to stop taking your TB drugs. But it is crucial that you finish the full course of therapy and take the medications exactly as prescribed by your doctor. Stopping treatment too soon or skipping doses can allow the bacteria that are still alive to become resistant to those drugs, leading to TB that is much more dangerous and difficult to treat.
To help people stick with their treatment, a program called directly observed therapy (DOT) is recommended. In this approach, a health care worker administers your medication so that you don't have to remember to take it on your own.
The WHO advises supervised treatment, (e.g. directly observed treatment (DOT)), to ensure treatment adherence and completion. The current treatment regimen for new cases of pulmonary TB consists of a three to six month treatment regimen with four different drugs which are
- Isoniazid
- Rifampicin
- pyrazinamide
- ethambutol
with daily or three times weekly dosing under DOT. These different medicines may be combined into single Fixed Dose Combination (FDC) tablets to reduce pill burden. The treatment success rate for drug-sensitive patients with this regimen is high.
Patients with previously treated TB have a high chance of a drug-resistant strain of TB and require a different approach depending on the availability of drug-sensitivity testing (DST). Where DST is routinely available, a new treatment regimen should be commenced according to the results. In situations where DST is not routinely available, patients are treated empirically with an eight month retreatment regimen containing five first-line drugs or an MDR-TB regimen including second-line drugs. The MDR-TB regimen can last from 18 months to up to 30 months and contains at least four different drugs including the use of at least one injectable medicine but has a relatively low success rate Several of the first-line or second-line TB treatments can cause liver damage and show drug-drug interactions with HIV therapy (antiretroviral drugs, ARVs). In addition these regimens have a high pill burden and require commitment from the patient and care providers.
The current treatment for LTBI recommended by WHO consists of a six month treatment with daily or three-weekly intake of four different drugs (isoniazid, rifampicin, pyrazinamide, and ethambutol).3 The United States Centers for Disease Control (CDC) and the United Kingdom National Institute for Health and Clinical Excellence (NICE) have recently approved a three month once-weekly regimen of isoniazid plus rifapentin (CDC) or rifampicin (NICE). However, this novel treatment is not suitable for young children, pregnant women, and HIV-positive patients on ARVs.[18]
A number of new drugs are being looked at as add-on therapy to the current drug-resistant combination treatment including:
Completing treatment is essential
After a few weeks, you won't be contagious and you may start to feel better. It might be tempting to stop taking your TB drugs. But it is crucial that you finish the full course of therapy and take the medications exactly as prescribed by your doctor. Stopping treatment too soon or skipping doses can allow the bacteria that are still alive to become resistant to those drugs, leading to TB that is much more dangerous and difficult to treat.
To help people stick with their treatment, a program called directly observed therapy (DOT) is recommended. In this approach, a health care worker administers your medication so that you don't have to remember to take it on your own.
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Prevention
Stopping the Spread of Tuberculosis
Anyone who comes into contact with an individual infected with tuberculosis bacteria is at risk of developing the disease, so one obvious solution is to steer clear of people who are sick, sneezing, and coughing. Follow these additional steps to help prevent the spread of tuberculosis infection:
Vaccines
The only available vaccine (Bacille-Calmette-Guérin, BCG) is almost 100 years old. This vaccine protects against severe progressive TB in children, but its protective effects in
adolescents and adults are variable. The vaccine is not suitable for use in HIV-positive children. New vaccines that are safe and effective against all forms of TB in all age groups, including the HIV-positive population, are needed.[18]
DISCLAIMER: This website is a part of academics and should be used only for educational purpose.
Stopping the Spread of Tuberculosis
Anyone who comes into contact with an individual infected with tuberculosis bacteria is at risk of developing the disease, so one obvious solution is to steer clear of people who are sick, sneezing, and coughing. Follow these additional steps to help prevent the spread of tuberculosis infection:
- People with tuberculosis infection should always cover their mouths when they cough or noses when they sneeze.
- People with latent tuberculosis infection — when there are no synptoms or active disease — should take medication to prevent it from becoming active tuberculosis disease
- People with TB should take all medications as required
- People at risk for or who have been in contact with people with tuberculosis infection should be tested[20]
Vaccines
The only available vaccine (Bacille-Calmette-Guérin, BCG) is almost 100 years old. This vaccine protects against severe progressive TB in children, but its protective effects in
adolescents and adults are variable. The vaccine is not suitable for use in HIV-positive children. New vaccines that are safe and effective against all forms of TB in all age groups, including the HIV-positive population, are needed.[18]
DISCLAIMER: This website is a part of academics and should be used only for educational purpose.