Background
To comprehend the effect of delayed care on risk of tuberculosis (TB) transmission in a TB prevalent but low case detection area, this study examined the association of diagnosis delay with patient infectiousness (cavitation and smear positivity) and determined the threshold delay that optimizes infectiousness. It also assessed transmission drivers in Somali region of Ethiopia, an area with ample pastoralist population.
Methods
A cross-sectional study was conducted using 434 new pulmonary TB patients, aged ≥15 years, who were recruited prospectively in five major facilities between December 2017 and October 2018. Data were collected on delays in diagnosis, socio-demographics, clinical and epidemiological information using interview, record-review, anthropometry, sputum microscopy and chest radiography techniques. Log-binomial regression models were used to reveal predictors of cavitation and smear positivity at p<0.05 using Stata/SE®14. C-statistics was applied to determine predictive ability and threshold delay that classifies infectiousness.
Results
Median age of participants was 30 years. Majorities were male (62.9%), nearly half (46.5%) were pastoralist and 2.3% TB/HIV co-infected. Median delay from debut of illness to diagnosis was 49 days (IQR=37). Among all cases, 45.6% [95%CI: 40.9-50.4] had pulmonary cavity and 42.0% [95%CI: 37.3˗46.9] were smear positive. On multivariable analysis, cavitation was higher in patients delayed over a month [P<0.001], ≤35 years [APR (95%CI) =1.3(1.01-1.6)], with chronic diseases [APR (95%CI) =1.8(1.2-2.6)] and low MUAC*female [APR (95%CI) =1.8(1.2-2.8)]. Smear positivity was higher in patients delayed >49 days [p=0.02], ≤35 years [APR (95%CI) =1.4(1.1-1.8)], low BMI [APR (95%CI) =1.3(1.01-1.7)] and low MUAC [APR (95%CI) =1.5(1.2-1.9)]. Delay discriminates cavitation [AUC (95%CI) =0.67(0.62-0.72)] at 43 days optimal cutoff and 74.6% sensitivity.
Conclusion
This study highlights that delay in diagnosis of pulmonary TB remains high and is associated with increased risk of cavitation and smear positivity in pastoral setting in Ethiopia. In pastoral settings, this may call upon a socio-cultural tailored TB prevention and control strategies.