Diagnosis of Tuberculosis

Frequently, both a chest X-ray and CT scan reveal images that make one suspect the disease is present.

When looking at a tissue biopsy, a characteristic type of inflammation (granulomas with necrosis) can also be suspected.

If the patient does not produce sputum during the diagnostic process for pulmonary tuberculosis, the gastric contents may be aspirated by a tube introduced through the nose, or respiratory secretions may be directly obtained from the patient through fibreoptic bronchoscopy.

A certain diagnosis is established when the causative microorganism (Mycobacterium tuberculosis) is found in respiratory secretions or in a sample obtained directly by puncture or biopsy of the affected organ.

After staining the samples, the microbe that causes tuberculosis can be seen under a microscope. Their genes are detected by microbiological genetic amplification procedures.

Finally, the tuberculosis microbe can be obtained by seeding clinical samples (respiratory secretions, biopsies, fluids) in special culture media. Because the microbe grows slowly, culture and antibiotic susceptibility test results may take several weeks.

No microbiological test is positive for all patients, so a precise diagnosis is sometimes difficult to obtain.