Economic challenges associated with tuberculosis diagnostic development

Gaps related to screening and diagnosis of tuberculosis in care cascade in selected health facilities in East Africa countries: A retrospective study

Introduction

East Africa countries (Tanzania, Kenya, and Uganda) are among tuberculosis high burdened countries globally. As we race to accelerate progress towards a world free of tuberculosis by 2035, gaps related to screening and diagnosis in the cascade care need to be addressed.

Methods

We conducted a three-year (2015–2017) retrospective study using routine program data in 21 health facilities from East Africa. Data abstraction were done at tuberculosis clinics, outpatient departments (OPD), human immunodeficiency virus (HIV) and diabetic clinics, and then complemented with structured interviews with healthcare providers to identify possible gaps related to integration, screening, and diagnosis of tuberculosis. Data were analyzed using STATA™ Version 14.1.

Results

We extracted information from 49,454 presumptive TB patients who were registered in the 21 facilities between January 2015 and December 2017. A total of 9,565 tuberculosis cases were notified; 46.5% (4,450) were bacteriologically confirmed and 31.5% (3,013) were HIV-infected. Prevalence of tuberculosis among presumptive pulmonary tuberculosis cases was 17.4%. The outcomes observed were as follows: 79.8% (7,646) cured or completed treatment, 6.6% (634) died, 13.3% (1,270) lost to follow-up or undocumented and 0.4% (34) treatment failure. In all countries, tuberculosis screening was largely integrated at OPD and HIV clinics. High patient load, weak laboratory specimen referral system, shortage of trained personnel, and frequent interruption of laboratory supplies were the major cited challenges in screening and diagnosis of tuberculosis.

Conclusion

Screening and diagnostic activities were frequently affected by scarcity of human and financial resources. Tuberculosis screening was mainly integrated at OPD and HIV clinics, with less emphasis on the other health facility clinics. Closing gaps related to TB case finding and diagnosis in developing countries requires sustainable investment for both human and financial resources and strengthen the integration of TB activities within the health system.

Antigens Rv0310c and Rv1255c are promising novel biomarkers for the diagnosis of Mycobacterium tuberculosis infection

This study aimed to identify novel immunogenic epitopes from Mycobacterium tuberculosis (MTB) that could be used in tuberculosis (TB) diagnostics. To determine the diagnostic potential of mycobacterial antigens in serodiagnosis of TB, 256 patients were enrolled in a study and divided into two groups: 126 smear-positive pulmonary TB patients (SPPT) and 130 smear-negative pulmonary TB patients (SNPT); 152 bacillus Calmette-Guerin (BCG)-vaccinated healthy people were used as a control. Murine results showed that antigens Rv0310c-E from RD 8 and Rv1255c-E from RD 10 were strongly immunogenic to Th1 cells and induced a great humoral response. Receiver operating characteristic analysis indicated that Rv0310c-E (area under the curve (AUC): 0.800) and Rv1255c-E (AUC: 0.808) performed better than ESAT-6 (AUC: 0.665) and CFP-10 (AUC: 0.623) proteins but were comparable with Rv3425 (AUC: 0.788) protein in a human serum IgG analysis. Rv0310c-E demonstrated the highest diagnostic ability for the SPPT group (Youden index: 0.5602, sensitivity: 69.84%, specificity: 86.18%), while Rv1255c-E demonstrated the highest diagnostic ability for the SNPT group (Youden index: 0.5674, sensitivity: 73.84%, specificity: 82.89%). In addition, combination analysis found that antigen Rv0310c-E, coupled with the Rv3425 protein (Youden index: 0.6098, sensitivity: 87.30%, specificity: 73.68%) had the strongest performance for TB diagnostics of the SPPT group, and the single antigen Rv1255c-E was strongest for the SNPT group. These results suggest that antigens Rv0310c-E and Rv1255c-E are potential antigens for TB serodiagnostic tests, which may facilitate detection of MTB in smear-negative and smear-positive patients.

PET/CT imaging of Mycobacterium tuberculosis infection

Tuberculosis has a high morbidity and mortality worldwide. Mycobacterium tuberculosis (Mtb) has a complex pathophysiology; it is an aerobic bacillus capable of surviving in anaerobic conditions in a latent state for a very long time before reactivation to active disease. In the latent tuberculosis infection, the individual has no clinical evidence of active disease, but exhibits a hypersensitive response to proteins of Mtb. Only some 5–10 % of latently infected individuals appear to have reactivation of tuberculosis at any one time point after infection, and neither imaging nor immune tests have been shown to predict tuberculosis reactivation reliably. The complex pathology of the organism provides multiple molecular targets for imaging the infection and targeting therapy. Positron emission tomography (PET) integrated with computer tomography (CT) provides a unique opportunity to noninvasively image the whole body for diagnosing, staging and assessing therapy response in many infectious and inflammatory diseases. PET/CT is a powerful noninvasive tool that can rapidly provide three-dimensional views of disease deep within the body and conduct longitudinal assessment over time in one particular patient. Some PET tracers, such as ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG), have been found to be useful in various infectious diseases for detection, assessing disease activity, staging and monitoring response to therapy. This tracer has also been used for imaging tuberculosis. ¹⁸F-FDG PET relies on the glucose uptake of inflammatory cells as a result of the respiratory burst that occurs with infection. Other PET tracers have also been used to image different aspects of the pathology or microbiology of Mtb. The synthesis of the complex cell membrane of the bacilli for example can be imaged with ¹¹C-choline or ¹⁸F-fluoroethylcholine PET/CT while the uptake of amino acids during cell growth can be imaged by 3′-deoxy-3′-[¹⁸F]fluoro-l-thymidine. PET/CT provides a noninvasive and sensitive method of assessing histopathological information on different aspects of tuberculosis and is already playing a role in the management of tuberculosis. As our understanding of the pathophysiology of tuberculosis increases, the role of PET/CT in the management of this disease would become more important. In this review, we highlight the various tracers that have been used in tuberculosis and explain the underlying mechanisms for their use.