Abstract
ObjectiveTo compare the performance of frontloading and the standard WHO method for diagnosis of pulmonary TB at Mulago Hospital in order to validate the technique in this setting.MethodsThis was a cross-sectional study in which 229 adult (≥18 years) TB suspects were consecutively enrolled. Suspects submitted three sputum samples as follows: at initial presentation, one hour after the first sample, and the next morning. The first and next morning samples formed the standard WHO method, while the first and the one hour later samples formed the frontloading method. Sample processing was by the standard N-acetyl L-cystein (NALC)-NaOH method, and fluorescent microscopy was done for both methods, while cultures of the first sample on Lowenstein-Jensen slants acted as a gold standard. The sensitivity, specificity and predictive values for the WHO standard and frontloading methods were compared.ResultsThe sensitivity of both the frontloading and standard schemes was 91.1% while their specificities were 86.2% and 91.7% respectively. There was excellent agreement between the diagnostic capacity of the two methods (kappa statistic = 0.87, P<0.0001). The positive predictive value for the frontloading scheme was 87.2% and that for the standard approach was 91.9%, while the negative predictive values were 90.4% and 90.9%, respectively. Among the HIV positive patients, frontloading identified 59/79 (74.7%) culture positive samples while the standard approach identified 55/79 (69.6%). In the HIV sero-negative category, on the other hand, front-loading identified 48/110 (43.6%) culture positive samples compared to 45/110 (40.9%) by the standard approach.ConclusionFrontloading based on smear examination of two same-day sputum samples has a similar performance to the current standard method and would not be associated with any significant missed diagnosis. It may therefore be advocated for use in our setting so as to reduce time to completion of diagnosis and patient loss to follow-up.
Highlights
Tuberculosis (TB) is one of the most common infectious causes of mortality in the world with control in a majority of the patients, who are mostly in resource-limited settings, hindered by many economic barriers that include costly pathways to diagnosis [1]
Diagnosis of pulmonary tuberculosis (PTB) in low and middle income countries greatly depends on smear microscopy, using 2 sputum samples
The first sample is collected at the time of consultation and the second sample is an early morning sample provided on the morning
Summary
Tuberculosis (TB) is one of the most common infectious causes of mortality in the world with control in a majority of the patients, who are mostly in resource-limited settings, hindered by many economic barriers that include costly pathways to diagnosis [1]. Because of poor radiological services, many places in Uganda still do up to three sputum samples before starting treatment, further compounding this dilemma [3] Another technique, referred to as front-loading, has been proposed where two sputum samples are collected and analyzed on the same day [4]. Front-loading would offer immediate results, help on treatment decision making and reduce on the dropout rate and control disease spread This technique was be able to diagnose from 76% to 97% patients with PTB in two different studies, comparable to the standard scheme which identifies from 73% to 97% [5,6], while a multicountry study found the sensitivity of the dame technique at 63.6% (95% CI 59.7%–67.5%), which was non-inferior to spotmorning (64.8%, 95% CI 61.3%–68.3%) recommended by the WHO [7]
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