Rapid Research in Diagnostics Development for TB Network

The Rapid Research in Diagnostics Development for TB Network (R2D2 TB Network) study seeks to identify and rigorously assess promising early stage tuberculosis (TB) triage, diagnostic and drug resistance tests (hereafter referred to as "novel tests") in clinical studies conducted in settings of intended use. Rapid diagnosis, identification of drug resistance and effective treatment are critical for improving patient outcomes and reducing TB transmission. However, analysis of care cascades and prevalence surveys indicate that 40-60% of patients with TB are not initiated on effective treatment.1,2 The different types of tests required to reduce this "diagnostic gap" have been described in the form of target product profiles (TPPs). The highest- priority TPPs are for: 1) a point-of-care, non-sputum biomarker-based test to facilitate rapid TB diagnosis using easily accessible samples (a biomarker-based diagnostic test) and 2) a simple, low-cost test that can be used by front-line health workers to rule-out TB (a triage test). The R2D2 TB Network study will evaluate the sensitivity and specificity of novel triage and diagnostic tests against a reference standard including sputum Xpert® MTB/RIF (Mycobacterium tuberculosis/Rifampin) Ultra and sputum mycobacterial culture. The sensitivity and specificity of rapid drug susceptibility tests (rDST) will be compared against a reference standard including culture-based phenotypic DST and whole genome sequencing (WGS) of mycobacterial DNA. In addition, the usability of novel tests will be assessed through direct observations and surveys of routine health workers.

Novel TB triage and diagnostic tests:

We will include non-hospitalized adults (age ≥ 12 years) with either 1) cough ≥2 weeks' duration, a commonly accepted criterion for identifying people with presumed pulmonary TB (to facilitate standardization across sites and comparison of test performance across sub-groups or 2) risk factors for which TB screening is recommended (HIV infection, self-reported close contact, history of mining work). People with risk factors will be included if they screen positive for TB based on WHO-recommended screening tools as specified below:

Positive TB screening definitions by risk factor:

• PLHIV (Risk Factor), CRP >5 mg/dL OR abnormal CXR (Positive TB screening definition)
• Self-reported Close Contact (Risk Factor), abnormal CXR (Positive TB screening definition)
• History of mining work (Risk Factor), abnormal CXR (Positive TB screening definition)

We will exclude people who:

• completed latent or active TB treatment within the past 12 months (to increase TB prevalence and reduce false-positive results, respectively);
• have taken any medication with anti-mycobacterial activity (including fluoroquinolones) for any reason, within 2 weeks of study entry (to reduce false-negatives);
• reside >20km from the study site or are unwilling to return for follow-up visits; or
• are unwilling to provide informed consent

Novel TB rDST assays:

We will include adults (age ≥12 years) who are positive for TB and RIF resistance according to routine diagnostic testing (based typically on Xpert MTB/RIF, Xpert MTB/RIF Ultra, or Hain MTBDRplus). We will exclude people who:

• have negative or contaminated results on all baseline (i.e., enrollment) sputum cultures
• are unable to provide at least two sputum specimens of 3 mL each within one day of enrollment
• are unable or unwilling to provide informed consent

Assessment of the usability of novel TB tests:

We will include health workers at each clinical site who are 1) aged ≥18 years and 2) involved in routine TB testing (collecting specimens for or performing TB tests). We will exclude staff who are unwilling to provide informed consent.