Old tuberculosis

Published on 05/05/2015 by admin

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Last modified 22/04/2025

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109 Old tuberculosis

Instruction

Examine this patient’s chest.

Salient features

History

• Fever and night sweats

• Malaise, fatigue, anorexia

• Weight loss

• Cough with sputum.

Examination

These patients tend to have signs of common chest diseases but signs are not cut and dried. There are several reasons for this, such as pleural thickening (Fig. 109.1), thoracotomy and pneumonectomy, associated COPD, associated chest infection, plombage or phrenic nerve crush.

image

Fig. 109.1 Right-sided pleural thickening and calcification, with reduction in volume of the right hemithorax, in previous tuberculosis.

(With permission from Albert et al. 2008.)

Diagnosis

Following are two examples of findings and diagnosis.

Patient 1

The candidate was asked to examine the chest from the front, as a result of which the old thoracotomy scar was not seen. The patient was wheezy. The trachea was deviated to the right. Percussion note was stony dull from the right second intercostal space downwards. Wheeze was present on the left side. This patient had a right pneumonectomy with COPD in the left lung. The candidate’s diagnosis of right-sided pleural effusion with underlying collapse and left-sided COPD was accepted.

Patient 2

The trachea was central. A phrenic nerve crush scar was seen. Percussion note was dull in the left infra-axillary region and there were associated crackles. The diagnosis of pleural thickening with associated chest infection was accepted; that of pleural effusion was not.

Questions

How would you manage a patient with old tuberculosis?

Old TB requires no antituberculosis treatment. However, the patient may require symptomatic treatment for wheeze and shortness of breath.

In which groups of patients is the risk of tuberculosis high?

• Asian and Irish immigrants

• The elderly

• Immunocompromised individuals, particularly those with AIDS

• Alcoholics

• Occupations at risk: doctors, nurses, chest physiotherapists.

Advanced-level questions

Would you isolate a patient with newly diagnosed, sputum-positive, pulmonary tuberculosis?

Yes. Segregation in a single room for 2 weeks is recommended for patients with smear-positive TB. Barrier nursing, however, is unnecessary. Adults with smear-negative or non-pulmonary disease may be in a general ward. A child with TB should be segregated until the source case is identified, as this person may be visiting the child.

How are contacts investigated?

• Inquiry into bacille Calmette–Guérin (BCG) vaccination site

• Tuberculin test or Mantoux. The test consists of 0.1 ml (5 tuberculin units) of PPD (purified protein derivative) administered intracutaneously, usually in the volar surface of the forearm. The reaction is read 48 to 72 h after injection (although a reading obtained up to 1 week later is accurate). The size of the reaction is determined by measurement of the induration (not erythema) across the forearm at the site of the injection. This test is not 100% sensitive for infection with Mycobacerium tuberculosis, and even among patients with confirmed TB and no apparent immunosuppression, 10–20% will have negative results on tuberculin skin tests.

• Whole-blood interferon-γ assay (based on the release of interferon-γ from T lymphocytes in response to stimulation with M. tuberculosis PPD).

• Chest radiography examination. A chest radiography is considered abnormal if it reveals parenchymal abnormalities; chest radiographys showing pleural thickening or isolated calcified granulomas are not considered to be suggestive of previous TB. Patients with abnormal chest radiography, especially those with opacities occupying >2 cm2 of the upper lobe, should be evaluated for active TB by sputum examination before therapy for latent TB is initiated.

How is latent tuberculosis diagnosed?

High risk patients. Induration of ≥5 mm in diameter on a tuberculin skin test is used to diagnose latent TB. This group includes persons with HIV infection, close contacts of persons with active TB, persons with an abnormal chest radiography showing upper-lobe fibrosis consistent with previous TB, and immunosuppressed patients who have been receiving the equivalent of at least 15 mg/day prednisone for at least 1 month.

Intermediate risk patients. Induration of ≥10 mm should be used to define latent infection.

To whom would you offer BCG vaccination?

BCG vaccination is offered to previously unvaccinated, persistently Heaf test-negative or grade 1 contacts aged <35 years unless there is a special occupational, travel or ethnic risk. Patients with known or suspected HIV infection should not be offered the vaccination.

What are the indications for chemoprophylaxis?

• Chemoprophylaxis may be given to those with strongly positive Heaf test reactions but no clinical or radiological evidence of TB (Thorax 1994;49:1193–1200).

• Chemoprophylaxis should be given to children <5 years who are close contacts of a smear-positive adult irrespective of their tuberculin test result.

• If chemoprophylaxis is not undertaken, follow-up with periodic chest radiography examinations for 2 years is recommended in all these groups.

Which rapid test allows early diagnosis of tuberculosis?

Polymerase chain reaction.

What questions would you ask an HIV-positive patient to exclude tuberculosis?

If they have cough (of any duration), fever (of any duration) or night sweats lasting 3 weeks or more during the previous 4 weeks. This accurately rules out TB in majority of HIV-positive patients. Adding chest radiography to symptom screening further improves sensitivity (N Engl J Med 2010;362:707)

When should antiretroviral therapy be started in a patient with tuberculosis and HIV infection?

Initiation of antiretroviral treatment during TB therapy in patients with confirmed TB and HIV coinfection reduces mortality by ~56%. The death rate rose from 5.4/100 person-years to 12.1/100 person-years when initiation of antiretroviral therapy was delayed until the completion of TB therapy. The interval between the completion of TB therapy and the initiation of antiretroviral therapy is important; a considerable number of deaths in a sequential therapy group occurs during this period.

What do you know about genes encoding interleukin and susceptibility to tuberculosis?

Human genetic studies have implicated both IL12B (the gene encoding interleukin-12β) and NOD2 in increased susceptibility to mycobacterial disease, and mouse mutants lacking Nod2, Ripk2 or Infg (encoding interferon-γ) are highly susceptible to TB. (Note: Mycobacterium tuberculosis induces mainly Th17 responses. To rid the body of fungi and certain extracellular bacteria requires inflammation of the type engendered by Th17 cells).

Robert Koch (1843–1910), Institute for Infectious Diseases, Berlin, was awarded the 1905 Nobel Prize for Medicine for his investigations and discoveries in relation to TB.

Kary Mullis of the USA was awarded the Nobel Prize for developing the technique of PCR.

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