Technology for tuberculosis, but why can’t we simply prevent it with proven tools that save lives?

Editor’s notes: Advances in diagnostic test technology have transformed the management of HIV and related infections.  For HIV, we have seen the introduction of self-administered test kits as well as new approaches to HIV viral load testing and nucleic acid based infant diagnosis.  Cryptococcal antigen screening can make prophylaxis and treatment more focused and potentially cost-effective.  For tuberculosis the biggest revolution has been the widespread introduction of the geneXpert® system.  The newest version, the Xpert® Ultra, is more sensitive than the original cartridge and is now being scaled up in countries including South Africa.  Agizew and colleagues conducted a study in Botswana to compare how the Xpert® MTB/RIF cartridge performed when used in centralized or peripheral health facilities.  Encouragingly there were few differences between the two levels, suggesting that the systems can be used close to the point of care.  However, the authors did note a surprisingly high level of unsuccessful tests (15%) both at the central lab and at the peripheral clinic.  Many of these test failures seem to have been because the sample was not processed correctly, and so should be amenable to better training for the health care workers performing the test.  The yield of testing varied greatly between the 13 sites. Between 1% and 23% of samples were positive for tuberculosis, with an average of 14%.  This may be because some sites were receiving specialized referrals.  Of the 447 positive samples, 8% were shown to be rifampicin resistant.  This figure is hard to interpret without more detail of the sample of patients in whom the test was performed.  Resistance is always higher among those who have been treated previously and may be higher in those referred to specialized centres.  Nonetheless, it demonstrates that there are a significant number of people with tuberculosis in Botswana who are very likely to have multi-drug resistant disease and need effective second line treatment.  Technology comes with a price tag.  In this study, the team bought test kits for $18 each, which makes it an expensive choice.  However, if it leads to prompt treatment of multi-drug resistant disease and more accurate diagnosis of tuberculosis, including among those living with HIV, this might still be cost-effective.

A small implementation research study from a single provincial referral centre in Zambia also examined the use and results of geneXpert® screening.  Masenga and colleagues found that 6.6% of 2374 samples tested by geneXpert® over the course of a year were positive for tuberculosis.  An additional 1301 samples were tested by sputum microscopy.  Their results suggest that geneXpert® was used mainly on people who were living with HIV, given that more than 90% of the positive samples came from people living with HIV.  5.9% of the 152 positive samples that were tested in the system were resistant to rifampicin, with no difference by gender.  This study leaves many questions unanswered, such as the sampling strategy, the history of previous treatment and the outcomes of the diagnosis in terms of treatment regimen and success.  However, it shines a light on the ways that new technology is now routine in some settings.  We need more research from diverse settings to paint the full picture of implementation outside traditional research centres.

Zenner and colleagues revisit the question of the risks and benefits of treatment for latent tuberculosis infection.  In a systematic review and network meta-analysis, they demonstrate once more that we have several effective ways to prevent tuberculosis among people living with HIV and that the harms are much smaller than the risks.  The question remains why we have failed so badly to scale up preventive therapy for tuberculosis alongside the success in scale up of antiretrovirals.

 

Peripheral clinic versus centralized laboratory-based XPERT® MTB/RIF performance: experience gained from a pragmatic, stepped-wedge trial in Botswana

Agizew T, Boyd R, Ndwapi N, Auld A, Basotli J, Nyirenda S, Tedla Z, Mathoma A, Mathebula U, Lesedi C, Pals S, Date A, Alexander H, Kuebrich T, Finlay A. PLoS One. 2017 Aug 17;12(8):e0183237. doi: 10.1371/journal.pone.0183237. eCollection 2017.

Background: In 2011, the Botswana National Tuberculosis Program adopted World Health Organization guidelines and introduced Xpert® MTB/RIF (Xpert®) assay to support intensified case finding among people living with HIV enrolling in care. An evaluation was designed to assess performance under operational conditions to inform the national Xpert® scale-up.

Methods: Xpert® was implemented from August 2012 through November 2014 with 13 GeneXpert® instruments (GeneXpert®) deployed in a phased approach over nine months: nine centralized laboratory and four point-of-care (POC) peripheral clinics. Clinicians and laboratorians were trained on the four-symptom tuberculosis screening algorithm and Xpert® testing. We documented our experience with staff training and GeneXpert® performance. Test results were extracted from GeneXpert® software; unsuccessful tests were analysed in relation to testing sites and trends over time.

Results: During 276 instrument-months of operation a total of 3630 tests were performed, of which 3102 (85%) were successful with interpretable results. Mycobacterium tuberculosis complex was detected for 447 (14%); of these, 36 (8%) were rifampicin resistant. Of all 3630 Xpert® tests, 528 (15%) were unsuccessful; of these 361 (68%) were classified as "error", 119 (23%) as "invalid" and 48 (9%) as "no result". The total number of recorded error codes was 385 and the most common reasons were related to sample processing (211; 55%) followed by power supply (77; 20%) and cartridge/module related (54; 14%). Cumulative incidence of unsuccessful test was similar between POC (17%, 95% CI: 11-25%) and centralized laboratory-based GeneXpert® instruments (14%, 95% CI: 11-17%; p = 0.140).

Conclusions: Xpert® introduction was successful in the Botswana setting. The incidence of unsuccessful test was similar by GeneXpert® location (POC vs. centralized laboratory). However, unsuccessful test incidence (15%) in our settings was higher than previously reported and was mostly related to improper sample processing. Ensuring adequate training among Xpert® testing staff is essential to minimize errors.

Abstract  Full-text [free] access

Rifampicin resistance in mycobacterium tuberculosis patients using GeneXpert® at Livingstone Central Hospital for the year 2015: a cross sectional explorative study

Masenga SK, Mubila H, Hamooya BM. BMC Infect Dis. 2017 Sep 22;17(1):640. doi: 10.1186/s12879-017-2750-9

Background: Since the recent introduction of GeneXpert® for the detection of Tuberculosis (TB) drug resistance mutations in both primary resistance and acquired resistance in Zambia, little has been documented in literature on the issue of rifampicin resistance especially in the face of a high National TB burden. The study aimed to determine the prevalence of rifampicin resistance in tuberculosis patients at Livingstone Central Hospital for the year 2015.

Methods: This was a cross sectional study conducted at Livingstone Central Hospital where we reviewed 152 records (from January 1, 2015 to 31st December 2015) involving patients who presented with clinically suspected TB or documented TB, whose samples were sent to the laboratory for GeneXpert® Mycobacterium tuberculosis/rifampicin testing. Statistical evaluations used a one-sample test of proportion and Fisher's exact test.

Results: The age of participants ranged from 8 months to 73 years old (median = 34). Of the participants with complete data on gender, 99 (66%) and 52 (34%) were males and females respectively. The TB co-infection with HIV prevalence was 98.3% (p < 0.001). Prevalence of rifampicin resistance was 5.9% and there was no statistical significant difference between being male or female (p = 0.721).

Conclusion: We were able to show from our study, evidence of rifampicin resistance at Livingstone Central Hospital. Hence, there was need for further in-depth research and appropriate interventions (i.e. close follow-up and patient care for drug resistance positive patients).

Abstract  Full-text [free] access

Treatment of latent tuberculosis infection: an updated network meta-analysis

Zenner D, Beer N, Harris RJ, Lipman MC, Stagg HR, van der Werf MJ.  Ann Intern Med. 2017 Aug 15;167(4):248-255. doi: 10.7326/M17-0609. Epub 2017 Aug 1.

Background: Treatment of latent tuberculosis infection (LTBI) is an important component of tuberculosis (TB) control, and this study updates a previous network meta-analysis of the best LTBI treatment options to inform public health action and programmatic management of LTBI.

Purpose: To evaluate the comparative efficacy and harms of LTBI treatment regimens aimed at preventing active TB among adults and children.

Data sources: PubMed, Embase, and Web of Science from indexing to 8 May 2017; clinical trial registries; and conference abstracts. No language restrictions were applied.

Study selection: Randomized controlled trials that evaluated human LTBI treatments and recorded at least 1 of 2 prespecified end points (hepatotoxicity and prevention of active TB).

Data extraction: 2 investigators independently extracted data from eligible studies and assessed study quality according to a standard protocol.

Data synthesis: The network meta-analysis of 8 new and 53 previously included studies showed that isoniazid regimens of 6 months (odds ratio [OR], 0.65 [95% credible interval {CrI}, 0.50 to 0.83]) or 12 to 72 months (OR, 0.50 [CrI, 0.41 to 0.62]), rifampicin-only regimens (OR, 0.41 [CrI, 0.19 to 0.85]), rifampicin-isoniazid regimens of 3 to 4 months (OR, 0.53 [CrI, 0.36 to 0.78]), rifampicin-isoniazid-pyrazinamide regimens (OR, 0.35 [CrI, 0.19 to 0.61]), and rifampicin-pyrazinamide regimens (OR, 0.53 [CrI, 0.33 to 0.84]) were efficacious compared with placebo. Evidence existed for efficacy of weekly rifapentine-isoniazid regimens compared with no treatment (OR, 0.36 [CrI, 0.18 to 0.73]). No conclusive evidence showed that HIV status altered treatment efficacy.

Limitation: Evidence was sparse for many comparisons and hepatotoxicity outcomes, and risk of bias was high or unknown for many studies.

Conclusion: Evidence exists for the efficacy and safety of 6-month isoniazid monotherapy, rifampicin monotherapy, and combination therapies with 3 to 4 months of isoniazid and rifampicin.

Abstract  Full-text [free] access

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