The Basics of Tuberculosis

Tuberculosis is an airborne bacterial infection caused by an organism called myobacterium tuberculosis. It’s spread through the air from person to person such as when someone with pulmonary tuberculosis coughs or sneezes. If inhaled, these droplets can easily infect a nearby individual such as a family member or healthcare worker. Note that though it is primarily an infection of the lungs, it can affect other organs and body systems as well.

Commit the basics of tuberculosis to memory by listening to episode 218 of the Straight A Nursing podcast after you’ve read this article.

Tuberculosis pathophysiology

Myobacterium tuberculosis is a rod-shaped bacterium (also known as a bacillus) that is transmitted via airborne droplets. Once inhaled, it lodges in the lungs, causing an inflammatory response. As the inflammation progresses, immune cells seal off the bacilli and this forms a lesion called a tubercle. The involved lung tissue becomes necrotic and scar tissue develops around the tubercle, isolating it where it can remain dormant for life in a healthy individual. This is considered a latent TB infection. 

In most people with healthy immune systems, the infection remains latent and they never experience any symptoms of illness. However, in immunocompromised individuals and about 5-10% of latent cases, the bacteria causes active disease. This is referred to as TB disease and, if left untreated, can be fatal.

Tuberculosis risk factors

According to the World Health Organization, tuberculosis mostly affects adults, but individuals at any age are at risk. However, those with a weakened immune system are at higher risk. In fact, individuals with HIV are 18x more likely to develop active disease than the general population. Other conditions that put someone at risk are severe kidney disease, malnutrition, organ transplant, head and neck cancer, and long-term use of corticosteroids. Another key population at higher risk are those living in crowded conditions such as homeless shelters, prisons and even college dorms.

Now that you know some of the basic pathophysiology and risk factors, let’s go through tuberculosis using the Straight A Nursing LATTE method. 

L: How does the patient with tuberculosis LOOK?

While latent TB has no outward signs, the hallmark signs/symptoms of active TB infection are:

• A persistent and productive cough lasting more than three weeks 
• Unexplained weight loss and lack of appetite
• Night sweats
• Fever – some sources state it usually occurs in the afternoon
• Abnormal fatigue
• Swollen lymph nodes
• Shortness of breath, hemoptysis and chest pain can develop as the disease progresses.

A: How do you ASSESS a patient with tuberculosis?

• Get a full set of vital signs, paying special attention to oxygen saturation and temperature 
• Auscultate lungs – you  may hear coarse crackles or bronchial breath sounds which indicate consolidation has occurred
• Palpate lymph nodes to assess for swelling
• Weigh the patient and assess for recent, unexplained weight loss
• Assess travel history, possible exposures, living conditions and for any conditions that weaken the immune system (in other words, are they at risk?)

T: What TESTS will be ordered for a patient with tuberculosis?

• The definitive test for tuberculosis is detecting the pathogen via a culture. Cultures can be obtained from sputum, pleural fluid, a tissue biopsy, or bronchoalveolar lavage. 
• An acid fast bacilli smear may be conducted though false negatives are common enough that a negative smear does not indicate NO disease is present. Additionally, false positives can also occur. For this reason, it is considered a standard practice in the U.S. to run three specimens. 
• Another commonly used test is the IGRA – interferon gamma release assay. You’ll often see this referred to by its more common name which is the QuantiFERON-TB test. This is a blood test that detects the presence of a specific interferon in both active and latent infection.
• A nucleic acid amplification test can also be conducted. A positive result in an individual at risk for TB is typically considered sufficient for diagnosis.
• A tuberculin skin test can also detect infection and is used to support a diagnosis of TB. In other words, if the test is positive, this is supportive of a diagnosis of active TB. However, if the test is negative, it doesn’t rule out active infection.  
• Imaging may be utilized as part of the patient’s initial evaluation. This could be a chest x-ray or chest CT. 
• Because drug-resistant TB is considered a public health crisis, positive samples will be tested for susceptibility to antibiotics and can take from one week to one month, depending on the medium used.

Tuberculin skin test

All healthcare workers (and nursing students) in the U.S. must get a tuberculin skin test annually. You may also hear this called a Mantaux test or PPD – all three terms are used interchangeably. The test is conducted by injecting a small amount of a tuberculin derivative intradermally on the inner aspect of the forearm. The skin test is evaluated 48 to 72 hours later for the presence of induration, which is thickening of the skin. If present, the area of induration is measured:

• If 5 or more millimeters, this is considered a positive result in someone at high risk for TB such as those with HIV, organ transplant, compromised immune systems or had recent contact with an infected individual.
• If the induration is 10 or more millimeters this is considered positive in anyone from a country where TB is prevalent, anyone who abuses drugs, or anyone with a medical condition that puts them at risk (such as severe renal disease or diabetes).
• If the induration is greater than 15 millimeters, this is considered a positive result for anyone, even with no risk actors. 

T: What TREATMENTS will be provided for someone with tuberculosis?

The mainstay of treatment is medication, which can involve combination therapy of up to four medications for an extended period of time – typically 6 to 12 months. Because of the high risk for drug-resistance to develop, adherence to the regimen is crucial. For this reason, most (if not all) individuals undergoing drug therapy for TB will participate in what is called directly observed therapy (DOT). In directly observed therapy, an individual from the public health department or a healthcare worker directly observes the patient taking the medication either in person or via a telehealth visit.

Treatment for drug-susceptible strains is usually combination therapy that can include up to four medications (PIER) – pyrazinamide, isoniazid, ethambutol and rifampin. 

• Pyrazinamide (PZA) – This drug can cause liver damage, so teach your patients to avoid alcohol and report any signs of hepatic involvement such as yellowing of the skin or malaise. 
• Isoniazid (INH) – Teach the patient to take isoniazid on an empty stomach and that concurrent use of B6 (pyridoxine) helps prevent neurotoxicity. They should report any tingling of the extremities or signs of hepatic involvement.
• Ethambutol (EMB)…ethambutol can cause optic neuritis, which is inflammation of the optic nerve and can cause visual loss and loss of color perception. 
• Rifampin ( RIF) – This medication turns the urine and other secretions orange. You’ll need to advise the patient to report signs of hepatotoxicity with this one as well.

Drug-resistant tuberculosis is more difficult to treat and will include additional medications. A common therapy utilized is BPAL therapy which includes the drugs bedaquiline, pretomanid and linezolid. 

Other treatment interventions are: 

• Oxygen therapy may be needed, depending on the severity of the disease.
• Avoid the spread of infection by placing the patient on airborne precautions in a negative pressure room and wearing an N95 mask. Though this can vary by facility, patients are generally left on airborne precautions until they have three consecutive negative sputum smears taken at least eight hours apart, been taking their medication for two weeks and improving clinically.

E:  How do you EDUCATE the patient/family?

The key teaching points for tuberculosis are going to be around the medication regimen and avoiding the spread of infection. 

• Patients must complete the entire course of treatment, even if they begin to feel better 
• DOT helps prevent the development of drug-resistant strains and is not punitive. 
• A common NCLEX-style question about rifampin will be centered on teaching your patient to expect orange colored urine and secretions.
• Patients taking medication should avoid alcohol and acetaminophen for the duration of the regimen. 
• Female patients who are taking oral contraceptives should utilize an additional form of birth control as rifampin can reduce their effectiveness.
• The signs of liver damage can include fatigue, nausea, vomiting, loss of appetite, dark-colored urine, abdominal pain, jaundice and unexplained bruising. 
• To prevent the spread of infection outside the hospital, the patient should avoid crowds or confined spaces such as public transport. They should also wear a surgical mask when around others and limit or avoid exposure to children or immunocompromised individuals. 
• Though not widely used in the US, there is a vaccine for TB – the BCG vaccine. It is typically administered to children and infants in countries where TB is prevalent, but it does not always prevent infection. 
• Teach your patient with latent TB that it turns into active infection in about 5 to 10% of cases. They should know the signs/symptoms of active infection so they can report them to their physician immediately.

I hope this overview of tuberculosis helps you prepare for NCLEX, clinical and nursing school exams! For more respiratory topics, click here.

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