Diagnosing Tuberculosis Pamela Hepple Medecins Sans Frontieres UK

Diagnosis of pulmonary TB is done very differently according to context

In developed countries Symptom/resultTestTimeframe 1Cough/bloody phlegmX-ray/ CT scan1 day 2Cough/bloody phlegmSmear microscopy (concentrated) 2-3 days 3Cough/bloody phlegmSputum culture (liquid + solid media) 2-4 weeks 4Positive cultureDrug-sensitivity testing (1 st line) 1-2 weeks 5Multi-drug resistantDST (2 nd line)1-2 weeks

A typical patient can receive a diagnosis of MDR TB within 3 weeks, and a tailored drug regimen within 4 weeks. High-risk suspects can have molecular- based tests for diagnosis and drug-resistance which can give results within one day.

In most high-burden countries Symptom/resultTest/procedureTimeframe 1Cough/bloody phlegmSmear microscopy2-3 days (if TB programme is functional) 2Smear-positiveCategory I treatment6 – 8 months 3Smear-positive at 6 months Category II treatment6 – 8 months 4Smear-positive at end Category 2 treatment Culture and DST on solid media* 2 – 3 months

It can take up to 18 months for a patient to be diagnosed with MDR TB The vast majority of TB patients do not have access to culture or molecular diagnostic techniques, so will never be diagnosed with and treated for MDR TB Most patients rely on smear microscopy for TB diagnosis – 60% sensitivity at best Culture is gold standard – has 100% sensitivity