Light-emitting diode fluorescent microscopy and Xpert MTB/RIF® assay for diagnosis of pulmonary tuberculosis among patients attending Ambo hospital, west-central Ethiopia

Abstract

BackgroundThe relatively simple and cheaper light-emitting diode fluorescent microscopy (LED-FM) was recommended by the World Health Organization (WHO) to replace the conventional tuberculosis (TB) microscopy in both high- and low-volume laboratories. More recently the WHO also endorsed one more technique, Xpert MTB/RIF® assay (Xpert), for improved TB diagnosis particularly among human immunodeficiency virus (HIV)-infected cases. However, the relative performance of both of these tools differs from setting to setting in reference to the conventional TB diagnostics. This study thus aimed to evaluate these tools for TB detection in individuals visiting Ambo Hospital, west-central Ethiopia.MethodsCross-sectional early-morning sputum samples were collected from presumptive TB patients between January and August 2015. Socio-demographic data were captured using a structured questionnaire. Clinical information was gathered from patients’ medical records. The sputum samples were diagnosed using LED-FM, Xpert, concentrated Ziehl-Neelsen (cZN) staining and Lowenstein-Jensen (LJ) culture as the gold standard. Drug sensitivity test (DST) was also conducted.ResultsOut of 362 sputum samples collected and processed, 36(9.9%) were positive by LED-FM, 42(11.6%) by cZN and 50(13.8%) by Xpert. But, only 340 samples could be declared culture positive or negative for mycobacteria. Of these 340, eight were non-tubercle mycobacteria (NTM). Out of the remaining 332 samples, 45(13.6%) had culture-confirmed TB with 11(24.4%) being HIV co-infected. LED-FM, Xpert and culture detected 54.5% (6/11), 90.9% (10/11) and 100% (11/11) mycobacteria in HIV-positive individuals and 81.3% (26/32), 73.7% (28/38), 78.8% (26/33) and 73.2% (30/41), in HIV negatives respectively. Two samples were rifampicin resistant by both Xpert and DST. The overall sensitivity, specificity, positive and negative predictive values of LED-FM and Xpert were 77.8, 100, 100 and 96; and 93.3, 98, 97.5 and 98.9% respectively.ConclusionThe data demonstrated the high diagnostic yield of Xpert. LED-FM sensitivity is higher compared to results quoted by recent systematic reviews although it appears to be lower than what was cited in the WHO policy statement (83.6%) during the recommendation of the technology. The high specificity of LED-FM in the study area is encouraging and is expected to boost its reliability and uptake.

Xpert MTB/RIF and Xpert MTB/RIF Ultra for pulmonary tuberculosis and rifampicin resistance in adults

“…We excluded it because of concern about duplicate data. In addition, the criteria for the reference standard for rifampicin resistance detection were not satisfiedFong 2017AbstractFriedrich 2011aThis study evaluated Xpert MTB/RIF for the diagnosis of pleural TBGama de Andrade 2017AbstractGelalcha 2017Includes both adults and children or no information about age of enrolmentGounder 2014Includes both adults and children or no information about age of enrolmentGriesel 2016AbstractGriesel 2017Includes data for pulmonary and extrapulmonary TB combinedGuenaoui 2016Includes both adults and children or no information about age of enrolmentGupta 2014AbstractGurbanova 2016AbstractGurbanova 2017Includes data for pulmonary and extrapulmonary TB combinedGursoy 2016Includes both adults and children or no information about age of enrolmentHabeenzu 2017Includes both adults and children or no information about age of enrolmentHanifa 2016Reference standard not satisfiedHeidebrecht 2016Data insufficient for 2 x 2 tableHillemann 2011This study evaluated Xpert MTB/RIF for the diagnosis of extrapulmonary TBHiza 2017Not a diagnostic accuracy studyHo 2016Community‐based screeningHoro 2017Includes both adults and children or no information about age of enrolmentHu 2014Includes both adults and children or no information about age of enrolmentHuang 2018Includes both adults and children or no information about age of enrolmentHuerga 2017Xpert was not the index testIoannidis 2010We could not obtain this article…”

Monitoring quality indicators for the Xpert MTB/RIF molecular assay in Ethiopia

“…We implemented the quality indicators recommended for Xpert MTB/RIF at the National TB Reference Laboratory (NTRL) of Ethiopia. Targets were set for the quality indicators from guidelines [11, 12] or literature [13–18] (Table 1). Any observed changes outside of the targets require an investigation for identifying potential causes.…”

Comparison of GeneXpert MTB/RIF assay and LED-FM microscopy for the diagnosis of extra pulmonary tuberculosis in Khyber Pakhtunkhwa, Pakistan

“… 8 On the basis of these findings, World Health Organization in 2011 replaced conventional FM by LED-FM and phase in LED-FM as an alternative to ZN microscopy. 9 …”