Asymptomatic Tuberculosis in the Namibia National Tuberculosis Prevalence Survey: Occurrence Under Various Case...

Area of Science:

• Public Health
• Infectious Diseases
• Epidemiology

Background:

• Asymptomatic tuberculosis (TB) is an emerging concern due to its presumed infectiousness without symptoms.
• Current World Health Organization (WHO) screening recommendations for TB lack standardized symptom definitions.
• The study addresses the variability in defining asymptomatic TB based on symptom presence.

Purpose of the Study:

• To determine the proportion of bacteriologically confirmed asymptomatic TB cases using different symptom-based definitions.
• To evaluate the impact of various symptom screening criteria on identifying asymptomatic TB.
• To inform standardized definitions for asymptomatic TB detection.

Main Methods:

• Secondary analysis of the Namibia TB prevalence survey data.
• Inclusion of participants interviewed for symptoms, chest radiography, and bacteriological testing.
• Computation of asymptomatic TB proportions and logistic regression for associated factors.

Main Results:

• Out of 123 TB cases, 48.8% reported cough, 16.3% fever, 20.3% weight loss, and 21.1% night sweats.
• Asymptomatic TB prevalence varied from 39.8% to 63.0% based on the definition used.
• Screening based on prolonged cough missed 63.0% of cases, while screening based on W4SS (weight loss, fever, night sweats, or cough) of any duration missed 39.8%.

Conclusions:

• Asymptomatic TB constitutes a significant public health issue, present in 39.8% of cases even with inclusive symptom screening.
• There is a critical need to standardize the symptoms used for defining asymptomatic TB.
• The study recommends using W4SS of any duration as a more inclusive screening criterion.