Abstract
BackgroundThe diagnosis of tuberculosis (TB) using smear microscopy has been based on testing two specimens: one spot and one early morning sputa. Recently, the World Health Organization (WHO) has recommended to replace, whenever possible, microscopy with GeneXpert® MTB/RIF performed on a single specimen. However, as the bacterial load is higher in early morning specimens than in spot specimens, one could expect lower sensitivity of GeneXpert® MTB/RIF performed only on spot specimens. In this study, we compared results of GeneXpert® MTB/RIF on spot specimens versus early morning specimens, under programmatic conditions in Cotonou, Benin.MethodsFrom June to September 2018, all sputa received from presumptive TB patients at the Supranational Reference Laboratory for Tuberculosis of Cotonou were included in the study. From each patient, two specimens were collected (one spot and one early morning) and GeneXpert® MTB/RIF was performed on both specimens.ResultsIn total, 886 participants were included in the study, of whom 737 provided both sputa and 149 (16.8%) gave only the spot specimen. For the 737 participants who provided both sputa, GeneXpert® MTB/RIF was positive for both specimens in 152 participants; for three participants GeneXpert® MTB/RIF was positive on spot specimen but negative on morning specimen while for another three, the test was positive on morning specimen but negative on spot specimen. The overall percentage of agreement was excellent (99.2%) with a positive and negative percent agreement greater than 98%.ConclusionFor TB diagnosis under programmatic conditions in Cotonou, GeneXpert® MTB/RIF in spot specimens gave similar results with the test in morning specimens. Performing GeneXpert® MTB/RIF in both specimens did not significantly increase the number of cases detected. To avoid losing patients from the diagnostic cascade, it is preferable to test sputa produced at the time of the first visit at the health center.
Highlights
The diagnosis of tuberculosis (TB) using smear microscopy has been based on testing two specimens: one spot and one early morning sputa
To the best of our knowledge there are no studies evaluating in programmatic conditions the possible added value of the Morning specimen (MS) when GeneXpert® MTB/RIF is used as initial diagnostic test
In total, 886 presumptive TB patients were included in the study of whom 480 (54.2%) were male, 859 (97.0%) had never suffered from TB while 27 (3.0%) had a history of TB (Additional file 1, Table 1)
Summary
The diagnosis of tuberculosis (TB) using smear microscopy has been based on testing two specimens: one spot and one early morning sputa. We compared results of GeneXpert® MTB/RIF on spot specimens versus early morning specimens, under programmatic conditions in Cotonou, Benin. Massou et al BMC Infect Dis (2021) 21:979 testing multiple specimens yields an increase in sensitivity compared to culture, the reference method for TB detection. Nucleic acid amplification tests such as the GeneXpert® MTB/RIF (Cepheid, Sunnyvale, USA) have been developed This new technology showed a higher sensitivity than microscopy, is user-friendly and results are available within 2 h. To the best of our knowledge there are no studies evaluating in programmatic conditions the possible added value of the MS when GeneXpert® MTB/RIF is used as initial diagnostic test. We assessed the contribution of different specimens’ collection strategies for pulmonary TB screening using GeneXpert® MTB/RIF in Cotonou, Benin
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