The effect of sputum quality and volume on the yield of bacteriologically-confirmed TB by Xpert MTB/RIF and smear

Zimba, Onani; Tamuhla, Tsaone; Basotli, Joyce; Letsibogo, Gaoraelwe; Pals, Sherri; Mathebula, Unami; Mathoma, Anikie; Serumola, Christopher; Ramogale, Kitso; Boyd, Rosanna; Tran, Tiffany; Finlay, Alyssa; Auld, Andrew F.; Date, Anand; Alexander, Heather; Chihota, Violet; Agizew, Tefera

doi:10.11604/pamj.2019.33.110.15319

Cited by 6 publications

(4 citation statements)

References 17 publications

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“…However, we were limited by resource constraints; this would have enabled us to consolidate technical false-positives but would have not corrected misclassification bias in those with previous TB. Fourth, the lower than predicted proportion of trace readouts compared to previous reports ( Berhanu et al, 2018;Dorman et al, 2018) may have been due to suboptimal sample volume in some of the samples (not strictly recorded before running the Ultra assay) (Ho et al, 2015;Zimba et al, 2019) through our biobanking protocols stipulated collection of at least a one ml volume of sputum.…”

Section: Discussionmentioning

confidence: 88%

Comparison of Xpert MTB/RIF (G4) and Xpert Ultra, including trace readouts, for the diagnosis of pulmonary tuberculosis in a TB and HIV endemic setting

Esmail

Tomasicchio

Meldau

et al. 2020

International Journal of Infectious Diseases

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Background: There are limited data about Xpert-Ultra performance in different settings, in HIV-infected persons, in those with a history of previous TB, and with trace readouts. Methods: We evaluated the relative accuracy of Xpert-MTB/RIF and Xpert-Ultra in 272 selected but wellcharacterized archived sputum samples. Of these, 168 were culture-positive (64/168 smear-positive and 104/168 smear-negative), and 104 were culture-negative (102/104 from patients with previous TB and 2/ 104 from patients without a TB history). Assay-specific limit-of-detection (LOD) experiments were conducted using serial dilutions of Mycobacterium tuberculosis H37Rv. Results: Overall sensitivity (95%CI) in smear-negative culture-positive samples for Xpert-MTB/RIF and Xpert-Ultra were 71.2% (62.5-79.9) and 77% (68.9-85.1), respectively (and in HIV-infected persons: 63.5% (50-76.1) and 73.1% (61.1-85.2), respectively). The LOD for Xpert-Ultra was lower (9 versus 184 CFU/ml). There were a total of 9/272 (3.3%) Xpert Ultra trace readouts (6/104 [5.8%]) in smear-negative culturepositive persons, and 3/102 (3%) in culture-negative non-TB persons with a history of previous TB). Conclusions: Xpert-Ultra had a lower LOD compared to Xpert-MTB/RIF. A small proportion of samples (<5%) from culture-negative patients but with a history of previous TB had a likely false-positive trace readout. These data inform the management of patients with suspected TB in endemic settings.

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Section: Discussionmentioning

confidence: 88%

Comparison of Xpert MTB/RIF (G4) and Xpert Ultra, including trace readouts, for the diagnosis of pulmonary tuberculosis in a TB and HIV endemic setting

Esmail

Tomasicchio

Meldau

et al. 2020

International Journal of Infectious Diseases

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“…These merit additional investigation. On the other hand, sputum quality and quantity have an impact on the accuracy of TB diagnosis by smear or Xpert MTB/RIF (Cepheid, Sunnyvale, CA, USA) [ 17 – 19 ], and in the same vein, higher-quality sputum makes it simpler for rats to detect TB.…”

Section: Discussionmentioning

confidence: 99%

Increased tuberculosis case detection in Tanzanian children and adults using African giant pouched rats

Agizew,

Soka,

Fast

et al. 2024

BMC Infect Dis

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Background African giant pouched rats, trained by Anti-Persoonsmijnen Ontmijnende Product Ontwikkeling (APOPO), have demonstrated their ability to detect tuberculosis (TB) from sputum. We assessed rat-based case detection and compared the mycobacterium bacillary load (MTB-load) in children versus adults. Methods From January–December 2022, samples were collected prospectively from 69 Directly Observed Therapy (DOT) facilities’ presumed TB patients. Using an average of five rats, APOPO re-evaluated patients with bacteriologically negative (sputum-smear microscopy or Xpert MTB/RIF) results. Rat-positive samples were tested using concentrated smear light-emitting diode microscopy to confirm TB detection before treatment initiation. The rats’ identification of pulmonary TB is based on smelling TB-specific volatile organic compounds (VOCs) in sputum. Using STATA, Chi-square for odds ratio and confidence interval was calculated and evaluated: (1) the yield of rat-based TB detection compared to that of the health facilities; (2) rat-based TB detection in children versus adults; and (3) rats’ ability to detect TB across MTB-loads and between children and adults. Results From 35,766 patients, 5.3% (1900/35,766) were smear-positive and 94.7% (33,866/35,766) were smear or Xpert-negatives at DOTS facility. Of those with negative results, 2029 TB cases were detected using rats, contributing to 52% (2029/3929 of total TB identified), which otherwise would have been missed. Compared to DOT facilities, rats were six-fold more likely to detect TB among Acid Fast Bacilli (AFB) 1+/scanty [90% (1829/2029) versus 60% (1139/1900), odds ratio, OR = 6.11, 95% confidence interval, CI: 5.14–7.26]; twice more likely to identify TB cases among children [71% (91/129) versus 51% (1795/3542), OR = 2.3, 95% CI: 1.59–3.42]; and twice more likely to identify TB cases among children with AFB 1+/scanty than adults with the same MTB-load [5% (86/1703) versus 3% (28/1067), OR = 2.0, 95% CI: 1.28–3.03]. Conclusions Rats contributed over half of the TB cases identified in program settings, and children, especially those with a lower MTB-load, were more likely to be diagnosed with TB by rats. The chemical signatures, VOCs, were only available for adults, and further research describing the characteristics of VOCs in children versus adults may pave the way to enhance TB diagnosis in children.

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“…Sputum volume was assessed in millimeters by comparing to a reference container. 16 Study staff also collected key demographic and patient information.…”

Section: Public Health Actionmentioning

confidence: 99%

Improving sputum collection processes to increase tuberculosis case finding among HIV-positive persons in Botswana

Mathebula¹,

Emerson²,

Agizew³

et al. 2020

public health action

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Setting: Twenty-two human immunodeficiency virus (HIV) clinics in Botswana.Objective: To compare sputum collection rates, sputum quality and volume, and tuberculosis (TB) diagnosis rates before and after field efforts to improve sputum collection among individuals newly diagnosed with HIV with TB symptoms.Design: Newly diagnosed individuals living with HIV attending 22 HIV clinics in Botswana were screened for TB from August 2012 to March 2014. Starting in May 2013, a field intervention composed of the introduction of a tracking log for presumed TB patients, and patient instructions and sputum induction to improve sputum collection rates was implemented.Results: Prior to the intervention, sputum collection rates were 44.1% (384/870). Subsequently, sputum collection increased to 58.3% (579/993) (P < 0.001). Sputum quality and volume also improved. Although rates of TB diagnosis increased from 9.7% (84/870) to 12.5% (120/993), this difference was not significant (P = 0.143).Conclusion: Sputum collection rates among presumptive TB cases, as well as sputum quality and volume improved after implementation of the field intervention. To improve sputum collection rates, efforts at the program level should be ongoing.

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The effect of sputum quality and volume on the yield of bacteriologically-confirmed TB by Xpert MTB/RIF and smear

Cited by 6 publications

References 17 publications

Comparison of Xpert MTB/RIF (G4) and Xpert Ultra, including trace readouts, for the diagnosis of pulmonary tuberculosis in a TB and HIV endemic setting

Comparison of Xpert MTB/RIF (G4) and Xpert Ultra, including trace readouts, for the diagnosis of pulmonary tuberculosis in a TB and HIV endemic setting

Increased tuberculosis case detection in Tanzanian children and adults using African giant pouched rats

Improving sputum collection processes to increase tuberculosis case finding among HIV-positive persons in Botswana

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