What are the characteristics and persistence of a tuberculosis (TB) cough?

From the Guidelines

A tuberculosis (TB) cough is typically persistent, lasting more than 2-3 weeks without improvement, as stated in the International Standards for Tuberculosis Care 1. The characteristic features include a chronic, productive cough with mucus or phlegm that may contain blood (hemoptysis). The cough is often worse in the morning and can be accompanied by chest pain. Unlike typical respiratory infections, a TB cough doesn't resolve with standard antibiotics and persists despite treatment for other conditions. Other associated symptoms include fever, night sweats, fatigue, unintentional weight loss, and loss of appetite. The persistence of the cough is due to the slow-growing nature of Mycobacterium tuberculosis bacteria, which cause inflammation and damage in the lungs. This chronic inflammation leads to ongoing irritation of the airways, resulting in the persistent cough. Some key points to consider in the diagnosis of TB include:

• All persons with otherwise unexplained productive cough lasting 2–3 weeks should be evaluated for TB, as per Standard 1 of the International Standards for Tuberculosis Care 1.
• The diagnosis of sputum smear-negative pulmonary TB should be based on specific criteria, including at least three negative sputum smears and chest radiography findings consistent with TB, as outlined in Standard 5 of the International Standards for Tuberculosis Care 1. If someone experiences a cough with these characteristics lasting more than three weeks, especially with risk factors for TB exposure, they should seek medical evaluation promptly for proper diagnosis through sputum tests, chest X-rays, and other diagnostic methods. It's also important to note that effective anti-TB therapy can reduce infectiousness among persons who have active TB, but the period of time a patient must take effective therapy before becoming noninfectious varies between patients, as mentioned in guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care facilities 1.

From the Research

Characteristics of a TB Cough

• A TB cough is a characteristic symptom of tuberculosis and is the main cause of transmission 2, 3, 4
• Symptoms of pulmonary TB include a cough with or without sputum production lasting at least three weeks, chest pain, hemoptysis, fever, night sweats, weight loss, lack of appetite, chills, and weakness 2
• Cough dynamics in adults receiving tuberculosis treatment show that total time spent coughing is a better predictor of microbiologic indicators of disease severity and treatment response than the frequency of cough episodes or cough power 3

Persistence of a TB Cough

• The persistence of a TB cough can be affected by various factors, including prior tuberculosis, co-morbid diabetes, and drug resistance 3
• Patients with prior tuberculosis tend to cough more than patients without prior tuberculosis, and patients with tuberculosis and diabetes cough more than patients without diabetes co-morbidity 3
• Cough characteristics are similar regardless of HIV co-infection and for drug-susceptible versus drug-resistant tuberculosis 3
• Tuberculosis treatment response may be meaningfully assessed by objectively monitoring the time spent coughing 3

Diagnosis and Detection of TB Cough

• Diagnosis of TB cough can be done through sputum acid-fast bacillus tests, sputum cultures, and molecular detection of Mycobacterium tuberculosis 2, 5, 4
• Xpert MTB/XDR is a rapid nucleic acid amplification test for detection of tuberculosis and drug resistance in one test suitable for use in peripheral and intermediate level laboratories 4
• Xpert MTB/XDR provides accurate results for detection of isoniazid and fluoroquinolone resistance and can assist with selection of an optimised treatment regimen 4