Cough absent in most TB cases
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Key takeaways:
- Use of different subclinical TB definitions revealed no persistent cough in 82.8% of patients, no cough in 62.5% and no symptoms in 27.7%.
- Nearly 30% of those with TB and no persistent cough had positive smears.
Among patients with tuberculosis in high-incidence countries, more than 80% did not report persistent cough and more than 60% did not report cough all together, according to results published in The Lancet Infectious Diseases.
“Be alert that a patient who has risk factors for TB (eg, originating from or being in a high TB incidence country, type 2 diabetes, HIV, alcohol abuse) may have pulmonary TB in the absence of (persistent) cough,” Frank Cobelens, MD, MSc, PhD, professor of global health at Amsterdam University Medical Center and senior fellow at Amsterdam Institute for Global Health and Development, told Healio.
“For the public health professional in a TB high incidence setting, it means consider expanding active case finding of TB by chest X-ray screening at larger scale than is currently done,” Cobelens continued.
In an individual participant data meta-analysis, Cobelens and colleagues evaluated 12 surveys (n = 602,863; 50.7% younger than 35 years; 57.6% women) from Africa (59.4%) and Asia (40.6%) — both continents with high TB incidence between 2010 and 2019 — to determine the prevalence of subclinical pulmonary TB using three different case definitions.
The surveys collected chest X-ray and symptom screening data to determine if patients had TB. For this analysis, researchers standardized this criteria and defined TB as positive Mycobacterium tuberculosis sputum culture.
Of the three subclinical TB definitions, one considered the absence of persistent cough (cough lasting ≥ 2 weeks), one considered the absence of cough all together and the final one considered the absence of several symptoms, including cough, fever, chest pain, night sweats and weight loss.
A small proportion of the total cohort had TB (n = 1,944; 0.3%).
Within the population of patients with TB adjusted for both false-negative chest X-rays and uninterpretable culture results (n = 1,065), researchers found high proportions of patients without persistent cough (82.8%; 95% CI, 78.6%-86.6%) and patients without cough all together (62.5%; 95% CI, 56.6%-68.7%).
“From earlier systematic reviews it was already known that, when you look for them actively in the community, up to half of TB patients are ‘subclinical’ — but that was poorly defined and did not take underestimation of TB diagnoses into account,” Cobelens said. “We were surprised to see that when we did that, the symptom that is regarded as the most typical for TB, persistent cough, is absent in four out of five people that have active TB.”
Researchers also observed that 27.7% of patients with TB from four surveys did not report any symptoms suggestive of TB.
Out of four demographics (age, geography, region and self-reported gender), only gender was found to be significantly related to the likelihood for no persistent cough and no cough at all in TB. Hierarchical regression analysis (n = 1,813) revealed that men vs. women with TB have lower odds for no persistent cough (adjusted OR = 0.79; 95% CI, 0.63-0.97) and no cough at all (aOR = 0.76; 95% CI, 0.62-0.93).
Lastly, a positive smear examination signaling infectiousness was found in 29.1% (95% CI, 25.2%-33.3%) of patients with TB and no persistent cough, which Cobelens noted was surprising. Slightly fewer patients with TB and no cough had a positive examination (23.1%; 95% CI, 18.8%-27.4%).
Future studies on this topic are going to be different in many ways, Cobelens told Healio.
“One example is trials of new TB vaccines to show their clinical efficacy in preventing TB,” he said. “Currently these trials have as the ‘clinical endpoint’ symptomatic TB, often based on cough. We probably need to expand the definitions for these endpoints to include TB without cough or without any symptom at all,” Cobelens said.
“Another is that we need easier and cheaper diagnostic methods that can replace chest X-ray and allow scale-up of community TB screening in high-incidence communities, which requires R&D to develop those diagnostics and clinical studies to evaluate them for their yield, cost-effectiveness and acceptability to health workers and patients,” he added.
Reference:
- No persistent cough in 4 out of 5 with tuberculosis. https://www.amsterdamumc.org/en/spotlight/no-persistent-cough-in-four-out-of-five-with-tuberculosis.htm. Published March 13, 2024. Accessed March 14, 2024.