Xpert Ultra and Xpert HIV-VL in People Living With HIV

Summary

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Description

Sensitive and rapid point-of-care diagnostics should improve TB treatment outcomes, however, tests meeting these criteria have, until recently, been unavailable, especially in PLHIV. PLHIV often have early stage TB disease at the time of ART initiation and paucibacillary sputum. The current frontlin...

Sensitive and rapid point-of-care diagnostics should improve TB treatment outcomes, however, tests meeting these criteria have, until recently, been unavailable, especially in PLHIV. PLHIV often have early stage TB disease at the time of ART initiation and paucibacillary sputum. The current frontline test for TB is the Xpert MTB/RIF, which uses the GeneXpert platform, and is deployed primarily at centralised reference laboratories (Clouse et al., 2012; Hanrahan et al., 2015). This approach has two major limitations: 1) the instruments' far-patient placement likely undermines its potential clinical impact; 2) Xpert MTB/RIF has suboptimal sensitivity in PLHIV 3) the GeneXpert platform is primarily used only for TB testing and no other assays such as Xpert HIV-1 Viral Load (VL). Xpert MTB/RIF has been succeeded by Xpert MTB/RIF Ultra (Xpert Ultra), which promises to increase the speed and sensitivity of TB diagnosis. Although Xpert Ultra will doubtlessly improve the detection of symptomatic patients, its greatest incremental benefit will likely arise in patients with low bacillary load (e.g., unselected HIV-positive patients initiating ART). Thus, Xpert Ultra has the potential to alter how TB is diagnosed in PLHIV by detecting TB before the disease has a chance to progress and before substantial transmission has occurred. The investigators will, in addition to Xpert Ultra on sputum, also perform TB testing using the urinary lateral flow (LF) LAM test, which may detect mycobacteria in asymptomatic PLHIV patients (Lawn et al., 2011). Moreover, investigators will also perform Xpert Ultra and Fujifilm SILVAMP (FujiLAM) on urine in ART initiators. Oral sampling will be done which includes the use of Ultra on tongue swabs and oral washes, inhouse PCR testing MGIT960 liquid culture from PLHIV (ART initiators) as part of preliminary investigation will also be explored, as well the use of blood RNA signatures for TB diagnosis. These novel test investigations are exploratory, and the results will not yet be used for patient management. This study will address the following research questions: (1) What is the sensitivity and specificity for each approach, overall, and after stratification by viral load/CD4, and (2) What is the proportion of patients that could not expectorate sputum were detected by non-sputum based tests? The polyvalent utility of the GeneXpert hardware platform is, however, hitherto largely unexplored despite the widespread deployment of machines. HIV VL testing is currently done in South Africa according to the National HIV Treatment guidelines, which advise measuring HIV VL every six months for the first year of treatment and annually thereafter. HIV VL testing involves collection of a blood sample, transporting it to a centralised laboratory for VL quantification, reporting the result back to the clinic, and calling the patient back. If HIV VL is found to be over 1000 genomes per ml, the patient may not be adherent to the prescribed ART or may have drug-resistant HIV and, now that a failure of virologic suppression has been confirmed, the patient may be asked to give a second blood sample for drug susceptibility testing and may have a counselling visit scheduled, in order to improve the patient's adherence. There is, however, a large amount of discretion at local clinics as to what constitutes virologic failure and patients with increased VL may still receive these interventions, even if below the 1000 genomes per ml threshold. The investigators also intend to perform Xpert HIV-1 VL testing and, compared to patients who receive the standard-of-care of centralised VL testing, evaluate the proportion of patients without virologic suppression who are referred to a follow-up intervention (DST and/or adherence counselling). The investigators propose a study which implements Xpert Ultra (in unselected PLHIV) and Xpert HIV-1 VL (in PLHIV on ART) in Cape Town, South Africa. Furthermore, the GeneXpert platform's polyvalent feasibility, time-to-result and -treatment (Xpert Ultra and LF LAM), and effect on interventions to improve VL (Xpert HIV-1 VL) will be examined.

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