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Tuberculosis: diagnosis and care

Vikki Knowles, BSc (Hons), RN.

Clinical Nurse Specialist - Respiratory Medicine, Department of Respiratory Medicine, Kingston Hospital. With acknowledgement to Carol Hart, MBE, TB Nurse Specialist, Kingston Hospital

Tuberculosis (TB) remains the leading infectious cause of adult death in the world today, with eight million people developing active disease and three million deaths occurring each year as a result (NRTC, 2000).

Tuberculosis (TB) remains the leading infectious cause of adult death in the world today, with eight million people developing active disease and three million deaths occurring each year as a result (NRTC, 2000).

The resurgence of the disease in industrialised countries means all health professionals should be alert to the possibility of TB when faced with unexplained chest symptoms. The disease had been considered to be on the decline in the UK, but the number of people diagnosed with TB rose between 1987 and 1990, to just over 7000 annual cases reported, an increase of 20% (Rose, 1999).

Although numbers have now stabilised, they are not falling. The largest increase has occurred in the London region, which has seen 40% of cases, with numbers doubling over the past 10 years (TB Focus Group, 2000).

Recognising the disease
TB primarily affects the lungs. The signs and symptoms can be ambiguous, mimicking many other chest conditions, such as pneumonia or asthma, which often leads to a delay in identifying the condition (see box). The subsequent delay in starting treatment can facilitate the spread of the disease.

Diagnosis
A patient who presents with a persistent cough, is unresponsive to treatment, has persistent chest symptoms or unexplained weight loss should be investigated for TB (see box).

Any suspicious chest X-ray should prompt further action, including referral to either a chest or infectious diseases physician. The chest X-ray will usually show shadowing in the apical regions of the lungs in TB, but may also show enlargement of the hilar glands; in advanced cases, cavitation of the lungs may be detected.

Sputum specimens should be collected if TB is suspected and tested for acid-fast bacilli (AFB). Three specimens are required and should be collected on three subsequent mornings, as the number of organisms in each specimen is often very small. Patients who have sputum that tests positive to the bacilli are contagious. However, not all patients with TB will have positive smears, so sputum is also sent for culture. The culture results will give the absolute identification of the organism and identify drug sensitivities.

Sputum cultures will take a minimum of eight weeks before results are available, as TB is a slow-growing organism. Patients who are unable to produce any sputum may be referred for bronchoscopy and lavage to obtain sputum for culture.

Blood tests including full blood count, urea and electrolyte levels, erythrocyte sedimentation rate and liver function tests. The tuberculin skin test can help identify whether the individual has been exposed to TB. It is important to remember that patients who have HIV may fail to react to the tuberculin skin test, but a negative result does not exclude a diagnosis of the disease (Interdepartmental Working Group on Tuberculosis, 1998).

Patient management
Once diagnosis has been confirmed it is important to initiate anti-TB treatment, which usually consists of a combination of drug regimens to ensure that drug resistance does not occur.

Because TB is a notifiable disease, any cases must be reported to the public health authorities so that contact tracing and screening can be initiated. Treatment is then commenced and is given for at least six months. This initially consists of a combination of four drugs - rifampicin, isoniazid, pyrazinamide and ethambutol - that will be taken for two months while awaiting culture results and is followed by at least four months of further treatment with isoniazid and rifampicin alone (BTS, 1998).

Before treatment for TB was available, about half of those affected died. However, although treatment is extremely effective it is not without problems, such as drug side-effects and compliance issues.

The main three drugs used to treat TB - rifampicin, isoniazid and pyrazinamide (usually given in combination as Rifater) - are all hepatotoxic. The patient will need regular liver function blood tests to ensure no damage is occurring. The drugs can cause other side-effects (see box above), which can interfere with compliance if steps are not taken to address them (NRTC, 2000).

Ideally, the medication should be taken daily, all together, on an empty stomach. Patients require a great deal of support during this period, as adherence to the drug regimen is the main determinant of successful treatment. Poor compliance can lead to problems such as the development of multiresistant TB (BTS, 1998).

Other factors can also affect adherence. For example, patients from groups such as the homeless who have no regular access to the health services, patient's whose first language is not English or those who originate from areas where a diagnosis of TB carries a stigma may all have additional problems in managing treatment.

Safeguards have been set up to ensure that vulnerable people with TB receive the recommended treatment where there are concerns about adherence. Directly observed therapy (DOT) is one method of ensuring that the medication is taken as prescribed, as it is done under the supervision of the nurse. This can take place in the hospital and has been shown in New York, USA, to be an effective way of ensuring patients follow their medication regimen (BTS, 2000). It is often more convenient to adopt an intermittent regimen of three times weekly medication, rather than daily treatment, when DOT has been implemented, which is just as effective.

Nursing care
Most patients who develop TB are nursed at home and it is important to adopt a multidisciplinary approach to ensure a successful outcome. The team should include the consultant physician, the TB nurse specialist, the GP and the social worker. When patients have a dual diagnosis of HIV and TB it is important for the HIV and TB teams to maintain strong links.

Patients are only considered to be contagious if their smear is positive to TB.

Once admitted to hospital these patients are isolated for the first two weeks of treatment, but full barrier nursing is not necessary. Patients admitted to hospital who develop or are known to have multidrug-resistant TB should be nursed in negative-pressure ventilated rooms. All patients who develop multidrug-resistance TB should also be admitted to hospital and remain in a negative-pressure ventilation room until they are non-infectious (BTS, 2000).

When TB treatment is initiated the nurses will need to provide general health education and health promotion to reinforce the importance of adhering to treatment, linking up closely with the TB nurse specialist who will provide continuity of care once the patient is discharged. The TB nurse will also monitor any side-effects and spend time with the patient and their family to address any concerns. The continuing support of the TB nurse is crucial, as adherence is most likely to fail six to eight weeks after the start of treatment.

Conclusion
TB remains a significant problem today and it is vital that health-care staff are aware of the need to screen and identify patients for this condition. Failure to recognise the problem allows infectious patients to remain in the community, increasing the risk of spreading the disease.

TB can be controlled through a combination of early diagnosis, prompt treatment, preventive care for those likely to have been infected recently and, finally, prevention through BCG vaccination, which provides about 75% protection in the UK.

CAUSES AND RISK FACTORS
- TB is an infection caused by Mycobacterium tuberculosis. In 75% of cases it affects the lungs, but it can infect sites such as the cervical lymph glands, bone, the renal system, and can cause meningitis.

- It is spread through droplet infection but generally requires about eight hours' close contact for the infection to be contagious (NRTC, 2000).

- Around 90% of people with TB will not develop signs of illness, as their natural defences will protect them (NRTC, 2000). About 10% of those exposed will go on to develop clinical disease, with half of these doing so within five years (NRTC, 2000). Of the remaining 5%, the primary infection will relapse at a later stage in their life (NRTC, 2000).

- People who are immunocompromised are more likely to develop TB - having diabetes, cancer treatment or taking high-dose oral steroids are predisposing factors (BTS, 1998). Other factors are poor social conditions and being homeless; the refugee community is also more vulnerable. These social groups also have more difficulty accessing health services.

- The presence of HIV is the greatest risk to developing the disease, and TB is now the commonest cause of death in patients with AIDS worldwide (TB Focus Group, 2000).

SIGNS AND SYMPTOMS
- Cough

- Haemoptysis

- Night sweats

- Fatigue/weakness

- Anorexia and weight loss

- Low-grade fever

- Persistent chest infection symptoms

DIAGNOSIS
- Chest X-ray

- Three sputum tests for acid-fast bacilli

- Blood tests should include full blood count, urea and electrolytes, liver function test and erythrocyte sedimentation rate

DRUGS AND POSSIBLE SIDE-EFFECTS
Rifampicin

- Hepatotoxic

- Stains urine and secretions orange

- Interferes with oral contraceptive pill

Pyrazinamide

- Hepatotoxic

- Severe skin irritation

- Nausea and vomiting

Isoniazid

- Hepatotoxic

- Peripheral neuropathy

Ethambutol

- Toxic effects on the eye

British Thoracic Society. (1998)Chemotherapy and management of tuberculosis in the UK: Recommendations 1998. Thorax 53: 536-548.

British Thoracic Society. (2000)Control and prevention of tuberculosis in the United Kingdom: Code of practice. Thorax 55: 887-901.

Interdepartmental Working Group on Tuberculosis (1998)The Prevention and Control of Tuberculosis in the United Kingdom. London: Department of Health.

National Respiratory Training Centre. (2000)Respiratory Course for Hospital Nurses. Warwick: NRTC.

Rose, A.M.C. (1999)National TB survey in England and Wales: final results. Thorax 54: (suppl 3), A5.

TB Focus Group. (2000)TB Focus (Chelsea and Westminster Hospital, December). Moreton, Wirral: Priory Lodge Education.

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