Awareness is crucial to identifying pulmonary TB

TB remains prevalent and should not be missed, says Dr Raj Thakkar

TB remains prevalent throughout the world and growing antibiotic resistance is adding to the problem.

Without awareness among healthcare professionals cases may be missed, leading to potentially disastrous consequences for both the individual concerned and their contacts.

Diagnosis
Always be suspicious of TB in a patient who is in one of the at-risk categories, particularly if they have not received the BCG vaccination.

Risk factors for TB include poverty, overcrowded housing and immunodeficiency, including HIV. The prevalence of TB is also higher among immigrants. BCG vaccination is not 100 per cent protective and it is no guarantee that a patient is not already infected.

The features of TB are non-specific. They include malaise, fever, anorexia, weight loss and night sweats. Symptoms suggestive of pulmonary TB include a productive cough, haemoptysis and breathlessness. Malignancy should be excluded and other causes of cough should be considered.

TB may also present non-specifically in children and a low index of suspicion is required. The child may have a cough, but weight loss, failure to thrive or pyrexia of unknown origin may be the only presenting features.

When it is suspected, NICE guidelines suggest that a chest X-ray should be taken. A suspicious film warrants further investigation.

Three sputum samples — ideally spontaneously-produced — should then be sent for analysis, one of which should be a morning sample.

Direct microscopy and culture should be performed. Rapid diagnosis is provided by DNA/RNA probes and DNA testing. These tests should be carried out if results will alter management or when antibiotic sensitivities are required. Skin testing may be helpful in cases where sputum analysis is negative, as long as the patient has not had a BCG vaccination; a positive tuberculin test supports a diagnosis of TB.

Management
Management of pulmonary TB requires holistic care, motivated patients, dedicated healthcare workers and regular monitoring.

Combination drugs, contacting patients with regular follow-up and directly observing therapy all reduce treatment failure. The standard drug regimen consists of rifampacin and isoniazid for six months and additional ethambutol and pyrazinamide for the first two months. Pyridoxine may be used to protect those at risk of peripheral neuropathy.

Side-effects that should be discussed with patients include urine discolouration due to rifampacin and ethambutol-induced optic toxicity.

Emerging resistance
The British Thoracic Society has recommended alternative regimens for resistant TB. Resistance to both rifampacin and isoniazid confers multi-drug resistance (MDR TB). Such cases should be referred for specialist treatment.

More recently, extensively drug resistant TB (XDR TB) has emerged. Of 536 TB patients investigated in a recent South African study, 53 had XDR TB. All the patients were HIV positive and 52 died within 25 days.

Global analyses have demonstrated that 2 per cent of MDR TB is actually XDR TB.

NICE has drawn up a list of risk factors for drug-resistance, including a previous treatment for TB, contacts with resistant cases, poor compliance, originating from a high risk country, living in London and male gender.

Ensuring adherence to regimen using good quality anti-TB chemotherapy minimises resistance. Appropriate management of MDR TB, partly by avoiding the addition of further drugs one at a time, also reduces the risk of XDR.

In its comprehensive guidance on TB, NICE has drawn up criteria for those who qualify for BCG vaccination. The document also covers contact tracing, management of health-care workers and screening of immigrants.

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