Tuberculosis

Definition/diagnostic criteria TB is an infectious disease primarily affecting the lungs (pulmonary TB), but it can also affect other parts of the body (extrapulmonary TB). It is caused by bacteria from the Mycobacterium tuberculosis complex. The diagnostic criteria typically involve a combination of clinical assessment, radiological findings, and microbiological testing.

Active disease describes where there is evidence of symptomatic or progressive disease of the lung and/or other organs. If left untreated, one person with active pulmonary TB may infect as many as 10 to 15 people every year.

Latent disease is defined as a state of persistent immune response to stimulation by Mycobacterium tuberculosis antigens, with no evidence of clinically active TB (the person is asymptomatic and not infectious.)

Epidemiology TB remains a significant public health issue globally. In 2021, the annual TB incidence in England was 7.8 per 100,000. 76.4% of cases were in people born outside the UK. The disease is more prevalent in urban areas and is correlated with depravation.

Diagnosis
Clinical features of active disease:

• Pulmonary TB: Common symptoms include a persistent cough, weight loss, night sweats, and fever. Shortness of breath and haemoptysis are late signs.
• Extrapulmonary TB: Symptoms can vary significantly depending on the specific areas of the body it affects. Manifestations include lymphadenopathy (lymphatic TB), bone or joint pain (joint or skeletal TB), abdominal or pelvic pain (genitourinary or gastrointestinal TB), urinary symptoms (genitourinary TB), sterile pyuria (renal TB) meningitis symptoms (TB meningitis).

Investigations: If a person has suspected active tuberculosis (TB) infection arrange hospital admission if the person is highly symptomatic, systemically unwell, or has complex social needs such as homelessness. Arrange urgent referral to the local multidisciplinary TB team to confirm the diagnosis and ongoing management if hospital admission is unnecessary.

Investigations will include a chest X-ray, respiratory sputum samples (microscopy for acid-fast bacilli, mycobacteria culture, and specialist molecular tests/drug sensitivity testing, depending on local laboratory protocols) and additional investigations (e.g imaging, bronchoscopy and lavage) depending on the site of suspected disease.

Latent TB can be screened for using a Mantoux test or Interferon-gamma release assay (IGRA) test.

Treatment Antibiotic drug treatment with combination regimens — usually 6 months of isoniazid (with pyridoxine) and rifampicin, supplemented in the first 2 months with pyrazinamide and ethambutol. Treatment success is usually defined by completion of therapy with negative follow-up sputum smears.

Treatments for latent TB are determined based on the person’s clinical circumstances.

Prognosis The prognosis for TB, if treated effectively, is generally good. However, factors such as drug resistance, HIV co-infection, and other comorbidities can complicate treatment and affect outcomes.