Tuberculosis

Exam Cram

• Organism: mycobacterium tuberculosis

• Presentation: night sweats, fevers, haemoptysis,

• CXR: upper lobe cavitating lesions

• Lymph biopsy: central cavitating necrosis

• Management: RIPE- Rifampicin, Isoniazid, Pyrazinamide, Ethambutol (6 months)

Outline

Background

• Tuberculosis causes significant global mortality and morbidity

Assessment

History

• Respiratory: haemoptysis, sob, cough

• Systemic: night sweats, fevers, weight loss

• Risk factors- foreign travel

Examination

• Focal respiratory crackles

• As per location, e.g. cutaneous- rash

Investigations

• CXR- upper lobe consolidation

• CT- necrotic lymph mass

• Mantoux test- previous infection or vaccination

• Gold interferon- test of choice for vaccinated

• Sputum- high specificity, poor sensitivity

• Bronchial lavage- high specificity and better sensitivity

Diagnosis

Diagnostic criteria: largely clinical

Differentials: sarcoidosis- non necrotic lymphadenopathy

Classification: as per site & symptoms

Management

Acute: RIPE

• Isoniazid & rifampicin: 6 months

• Pyrazinamide & ethambutol: 2 months

Med Reg Notes

Classification by Site

Locations

Any location can be effected by tuberculosis

• Pulmonary

• Skin

• Urinary tract

Diagnosis

Unfortunately no investigation is straightforward in TB- all of them can be falsely negative. 

Mantoux Test

Injection of tuberculin (tuberculosis antigen) under skin and examine immune reaction

If positive suggests immune response to TB either from previous infection or vaccination. Therefore is a reasonable screening test in the unvaccinated. 

Gold Interferon

Investigation of choice for vaccinated. Again possible to be falsely negative. 

Chest XR

Typically shows upper lobe cavitating lesions

Commonly used in occupational health as non invasive screening tool for TB. 

Sputum culture and sensitivity

High chance of being falsely negative. However if positive, it has the added benefits of giving antibiotic sensitivities. 

x3 Cultures should be sent

Bronchial Lavage

Invasive procedure but can produce lavage containing responsible TB organism and hence facilitate sensitivies. 

Management

Duration

Location Duration (total)

Pulmonary TB 6 months- isoniazid & rifampicin, 2m pyrazinamide & ethambutol

"Latent" TB 3 months- isoniazid & rifampicin

Also seen isoniazid 6m (incidental positive skin prick)

PEP 3 months- isoniazid & rifampicin (post exposure prophylaxis)

CNS TB 12 months, 2m RIPE mx, prednisolone

Spinal TB 12 months

Pott's Syndrome 12 months

Multidrug restistant 12 months under ID advice

Comments

• Pott's Syndrome is a vertebral fracture caused by TB in situ

• Latent TB requires an ID specialist to make that distinction

Antibiotics

Standard therapy is: RIPE

• Rifampicin

• Isoniazid

• Pyrazinamide

• Ethambutol

Side Effect Profiles

These are common MCQs so worth learning!

Rifampicin: orange urine, CYP450 inducer, induces cortisol metabolism, hepatitis, vomiting

Isoniazid: peripheral neuropathy, hepatitis

Pyrazinamide: Gout ++, hepatitis

Ethambutol: Gout +, hepatitis, optic neuritis

20% have an asymptomatic rise in creatinine- continue drugs and monitor as usually resolve. 

Comments

Pyridoxine can used to treat isoniazid peripheral neuropathy.

Tuberculosis Peritonitis

• Peritoneal aspiration: lymphocytosis

• SAAG: classically < 11 but can be > 11 if also portal HTN

References

1. Dr Ria Smith·Infectious Diseases·May 27, 2021·Last updated:September 17 (2024) Tuberculosis (TB): Symptoms, signs, management, Geeky Medics. Available at: https://geekymedics.com/tuberculosis-tb/ (Accessed: 06 October 2024).

2. https://cks.nice.org.uk/topics/tuberculosis/

Written in 2025