Saskia den Boon

Rapid Diagnosis of Tuberculosis with the Xpert MTB/RIF Assay in High Burden Countries: A Cost-Effectiveness Analysis

A cost-effectiveness study by Frank Cobelens and colleagues reveals that Xpert MTB/RIF is a cost-effective method of tuberculosis diagnosis that is suitable for use in low- and middle-income settings.

HIV-Associated Pneumocystis Pneumonia

During the past 30 years, major advances have been made in our understanding of HIV/AIDS and Pneumocystis pneumonia (PCP), but significant gaps remain. Pneumocystis is classified as a fungus and is host-species specific, but an understanding of its reservoir, mode of transmission, and pathogenesis is incomplete. PCP remains a frequent AIDS-defining diagnosis and is a frequent opportunistic pneumonia in the United States and in Europe, but comparable epidemiologic data from other areas of the world that are burdened with HIV/AIDS are limited. Pneumocystis cannot be cultured, and bronchoscopy with bronchoalveolar lavage is the gold standard procedure to diagnose PCP, but noninvasive diagnostic tests and biomarkers show promise that must be validated. Trimethoprim-sulfamethoxazole is the recommended first-line treatment and prophylaxis regimen, but putative trimethoprim-sulfamethoxazole drug resistance is an emerging concern. The International HIV-associated Opportunistic Pneumonias (IHOP) study was established to address these knowledge gaps. This review describes recent advances in the pathogenesis, epidemiology, diagnosis, and management of HIV-associated PCP and ongoing areas of clinical and translational research that are part of the IHOP study and the Longitudinal Studies of HIV-associated Lung Infections and Complications (Lung HIV).

Causes of early mortality in HIV-infected TB suspects in an East African referral hospital.

Background:Respiratory infections are a leading cause of death in Africa, especially among HIV-infected patients. Data on the etiology of fatal respiratory diseases are largely based on autopsy studies. We evaluated causes of pneumonia associated with early mortality among hospitalized HIV-infected patients in Kampala, Uganda. Methods:Prospective cohort study of HIV-infected patients admitted to Mulago Hospital, Kampala, with at least 2 weeks of cough. Consecutively enrolled patients with negative Ziehl Neelsen sputum smears for acid-fast bacilli underwent bronchoscopy with bronchoalveolar lavage and examination for mycobacteria (smear, solid culture), Pneumocystis jirovecii (Giemsa stain), and fungi (KOH mount, India ink stain, Sabouraud culture). Early mortality was defined as death before the 2-month follow-up visit. Results:Follow-up data were available for 353 (87%) of 407 patients enrolled. Of participants with follow-up data, 112 (32%) died within 2 months. Among patients with early mortality, a diagnosis was confirmed in 74 (66%), including tuberculosis (TB) (56%), cryptococcal pneumonia (1%), Pneumocystis pneumonia (3%), pulmonary Kaposi sarcoma (4%), and pneumonia caused by 2 or more disease processes (3%). Conclusions:Mortality in HIV-infected TB suspects is high, with TB associated with the largest proportion of deaths. A significant proportion of patients die without a confirmed diagnosis.

Impact of Xpert MTB/RIF testing on tuberculosis management and outcomes in hospitalized patients in Uganda.

Rationale The clinical impact of Xpert MTB/RIF for tuberculosis (TB) diagnosis in high HIV-prevalence settings is unknown. Objective To determine the diagnostic accuracy and impact of Xpert MTB/RIF among high-risk TB suspects. Methods We prospectively enrolled consecutive, hospitalized, Ugandan TB suspects in two phases: baseline phase in which Xpert MTB/RIF results were not reported to clinicians and an implementation phase in which results were reported. We determined the diagnostic accuracy of Xpert MTB/RIF in reference to culture (solid and liquid) and compared patient outcomes by study phase. Results 477 patients were included (baseline phase 287, implementation phase 190). Xpert MTB/RIF had high sensitivity (187/237, 79%, 95% CI: 73–84%) and specificity (190/199, 96%, 95% CI: 92–98%) for culture-positive TB overall, but sensitivity was lower (34/81, 42%, 95% CI: 31–54%) among smear-negative TB cases. Xpert MTB/RIF reduced median days-to-TB detection for all TB cases (1 [IQR 0–26] vs. 0 [IQR 0–1], p<0.001), and for smear-negative TB (35 [IQR 22–55] vs. 22 [IQR 0–33], p = 0.001). However, median days-to-TB treatment was similar for all TB cases (1 [IQR 0–5] vs. 0 [IQR 0–2], p = 0.06) and for smear-negative TB (7 [IQR 3–53] vs. 6 [IQR 1–61], p = 0.78). Two-month mortality was also similar between study phases among 252 TB cases (17% vs. 14%, difference +3%, 95% CI: −21% to +27%, p = 0.80), and among 87 smear-negative TB cases (28% vs. 22%, difference +6%, 95% CI: −34 to +46%, p = 0.77). Conclusions Xpert MTB/RIF facilitated more accurate and earlier TB diagnosis, leading to a higher proportion of TB suspects with a confirmed TB diagnosis prior to hospital discharge in a high HIV/low MDR TB prevalence setting. However, our study did not detect a decrease in two-month mortality following implementation of Xpert MTB/RIF possibly because of insufficient powering, differences in empiric TB treatment rates, and disease severity between study phases.

Clinical and Radiographic Factors Do Not Accurately Diagnose Smear-Negative Tuberculosis in HIV-infected Inpatients in Uganda: A Cross-Sectional Study

Background Although World Health Organization guidelines recommend clinical judgment and chest radiography for diagnosing tuberculosis in HIV-infected adults with unexplained cough and negative sputum smears for acid-fast bacilli, the diagnostic performance of this approach is unknown. Therefore, we sought to assess the accuracy of symptoms, physical signs, and radiographic findings for diagnosing tuberculosis in this population in a low-income country with a high incidence of tuberculosis. Methodology We performed a cross-sectional study enrolling consecutive HIV-infected inpatients with unexplained cough and negative sputum smears for acid-fast bacilli at Mulago Hospital in Kampala, Uganda. Trained medical officers prospectively collected data on standard symptoms and signs of systemic respiratory illness, and two radiologists interpreted chest radiographs in a standardized fashion. We calculated positive- and negative-likelihood ratios of these factors for diagnosing pulmonary tuberculosis (defined when mycobacterial cultures of sputum or bronchoalveolar lavage fluid were positive). We used both conventional and novel regression techniques to develop multivariable prediction models for pulmonary tuberculosis. Principal Findings Among 202 enrolled HIV-infected adults with negative sputum smears for acid-fast bacilli, 72 (36%) had culture-positive pulmonary tuberculosis. No single factor, including respiratory symptoms, physical findings, CD4+ T-cell count, or chest radiographic abnormalities, substantially increased or decreased the likelihood of pulmonary tuberculosis. After exhaustive testing, we were also unable to identify any combination of factors which reliably predicted bacteriologically confirmed tuberculosis. Conclusions and Significance Clinical and radiographic criteria did not help diagnose smear-negative pulmonary tuberculosis among HIV-infected patients with unexplained cough in a low-income setting. Enhanced diagnostic methods for smear-negative tuberculosis are urgently needed.

Integrated Strategies to Optimize Sputum Smear Microscopy: A Prospective Observational Study

RATIONALE Smear-positive tuberculosis (TB) case detection rates are far below targets in most low-income countries. The standard approach to smear microscopy involves sputum collection over multiple days and examination of sputum smears by light microscopy (LM), an insensitive and time-consuming technique. OBJECTIVE To determine whether two alternative approaches can increase smear-positive case detection by increasing the efficiency (single-specimen microscopy) or sensitivity (light-emitting diode [LED] fluorescence microscopy [FM]) of TB suspect evaluation. METHODS We enrolled patients with cough of 2 weeks or more admitted to Mulago Hospital in Kampala, Uganda and collected spot and early morning sputum specimens. We compared the diagnostic accuracy of four prespecified strategies based on the number of sputum specimens collected (one specimen versus two specimens) and the type of microscopy (LM versus LED FM) using mycobacterial culture as a reference standard. MEASUREMENTS AND MAIN RESULTS Two hundred thirty-three of 464 (50%) patients had culture-positive TB. There was no difference in sensitivity between single-specimen and two-specimen strategies when smears were examined with LM (55 vs. 56%; difference, -1%; 95% confidence interval [CI], -5 to +2%) or LED FM (61 vs. 64%; difference, -3%; 95% CI, -7 to +1%). LED FM was more sensitive than LM with both the single-specimen (61 vs. 55%; difference, 6%; 95% CI, 2-10%) and two-specimen strategies (64 vs. 56%; difference, 8%; 95% CI, 3-12%). Findings were similar among the HIV-infected patient subset (n = 321 patients). CONCLUSIONS In low-income, high TB burden settings, single-specimen microscopy and LED FM, either alone or in combination, could considerably increase identification of smear-positive TB cases.

Role of interferon-gamma release assays in the diagnosis of pulmonary tuberculosis in patients with advanced HIV infection

BackgroundT-cell interferon-gamma release assays (IGRAs) may have a role in the diagnosis of active tuberculosis when evaluating patients for whom standard microbiology has limited sensitivity. Our objective was to examine the accuracy of a commercial IGRA for diagnosis of active tuberculosis in HIV-infected persons.MethodsWe enrolled HIV-infected patients admitted to Mulago Hospital in Kampala, Uganda with cough ≥ 2 weeks. All patients underwent standard medical evaluation. We collected peripheral blood specimens at enrollment and performed a commercial, ELISPOT-based IGRA according to the manufacturers recommendations. IGRA sensitivity and specificity were determined using mycobacterial culture results as the reference standard.ResultsOverall, 236 patients were enrolled. The median CD4+ T-lymphocyte count was 49 cells/μl and 126 (53%) patients were diagnosed with active pulmonary tuberculosis. IGRAs were not performed in 24 (10%) patients due to insufficient mononuclear cell counts. In the remaining 212 patients, results were indeterminate in 54 (25%). IGRAs were positive in 95 of 158 (60%) patients with interpretable results. The proportion of positive test results was similar across CD4+ count strata. IGRA sensitivity was 73% and specificity 54%. IGRA results did not meaningfully alter the probability of active tuberculosis in patients with negative sputum smears.ConclusionsAn ELISPOT-based IGRA detected a high prevalence of latent tuberculosis infection in a hospitalized population of tuberculosis suspects with advanced HIV/AIDS but had limited utility for diagnosis of active tuberculosis in a high prevalence setting. Further research is needed to identify stronger and more specific immune responses in patients with active tuberculosis.

The prevalence and clinical course of HIV-associated pulmonary cryptococcosis in Uganda

Background:The prevalence and clinical course of pulmonary cryptococcosis in Sub-Saharan Africa are not well described. Methods:Consecutive HIV-infected adults hospitalized at Mulago Hospital (Kampala, Uganda) between September 2007 and July 2008 with cough ≥2 weeks were enrolled. Patients with negative sputum smears for acid-fast bacilli were referred for bronchoscopy with bronchoalveolar lavage (BAL). BAL fluid was examined for mycobacteria, Pneumocystis jirovecii, and fungi. Patients were followed 2 and 6 months after hospital discharge. Results:Of 407 patients enrolled, 132 (32%) underwent bronchoscopy. Of 132 BAL fungal cultures, 15 (11%) grew Cryptococcus neoformans. None of the patients were suspected to have pulmonary cryptococcosis on admission. The median CD4 count among those with pulmonary cryptococcosis was 23 cells per microliter (interquartile range = 7-51). Of 13 patients who completed 6-month follow-up, 4 died and 9 were improved, including 5 who had started antiretroviral therapy but had not received antifungal medication. Conclusions:Pulmonary cryptococcosis is common in HIV-infected tuberculosis suspects in Uganda. Early initiation of antiretroviral therapy in those with isolated pulmonary infection may improve outcomes, even without antifungal therapy. This finding suggests that some HIV-infected patients with C. neoformans isolated from respiratory samples may have colonization or localized infection.

Evaluating tuberculosis case detection via real-time monitoring of tuberculosis diagnostic services.

RATIONALE Tuberculosis case-detection rates are below internationally established targets in high-burden countries. Real-time monitoring and evaluation of adherence to widely endorsed standards of tuberculosis care might facilitate improved case finding. OBJECTIVES To monitor and evaluate the quality of tuberculosis case-detection and management services in a low-income country with a high incidence of tuberculosis. METHODS We prospectively evaluated tuberculosis diagnostic services at five primary health-care facilities in Uganda for 1 year, after introducing a real-time, electronic performance-monitoring system. We collected data on every clinical encounter, and measured quality using indicators derived from the International Standards of Tuberculosis Care. MEASUREMENTS AND MAIN RESULTS In 2009, there were 62,909 adult primary-care visits. During the first quarter of 2009, clinicians referred only 21% of patients with cough greater than or equal to 2 weeks for sputum smear microscopy and only 71% of patients with a positive sputum examination for tuberculosis treatment. These proportions increased to 53% and 84%, respectively, in the fourth quarter of 2009. The cumulative probability that a smear-positive patient with cough greater than or equal to 2 weeks would be appropriately evaluated and referred for treatment rose from 11% to 34% (P = 0.005). The quarterly number of tuberculosis cases identified and prescribed treatment also increased four-fold, from 5 to 21. CONCLUSIONS Poor adherence to internationally accepted standards of tuberculosis care improved after introduction of real-time performance monitoring and was associated with increased tuberculosis case detection. Real-time monitoring and evaluation can strengthen health systems in low-income countries and facilitate operational research on the effectiveness and sustainability of interventions to improve tuberculosis case detection.

Population-Level Impact of Same-Day Microscopy and Xpert MTB/RIF for Tuberculosis Diagnosis in Africa

Objective To compare the population-level impact of two World Health Organization-endorsed strategies for improving the diagnosis of tuberculosis (TB): same-day microscopy and Xpert MTB/RIF (Cepheid, USA). Methods We created a compartmental transmission model of TB in a representative African community, fit to the regional incidence and mortality of TB and HIV. We compared the population-level reduction in TB burden over ten years achievable with implementation over two years of same-day microscopy, Xpert MTB/RIF testing, and the combination of both approaches. Findings Same-day microscopy averted an estimated 11.0% of TB incidence over ten years (95% uncertainty range, UR: 3.3%–22.5%), and prevented 11.8% of all TB deaths (95% UR: 7.7%–27.1%). Scaling up Xpert MTB/RIF to all centralized laboratories to achieve 75% population coverage had similar impact on incidence (9.3% reduction, 95% UR: 1.9%–21.5%) and greater effect on mortality (23.8% reduction, 95% UR: 8.6%–33.4%). Combining the two strategies (i.e., same-day microscopy plus Xpert MTB/RIF) generated synergistic effects: an 18.7% reduction in incidence (95% UR: 5.6%–39.2%) and 33.1% reduction in TB mortality (95% UR: 18.1%–50.2%). By the end of year ten, combining same-day microscopy and Xpert MTB/RIF could reduce annual TB mortality by 44% relative to the current standard of care. Conclusion Scaling up novel diagnostic tests for TB and optimizing existing ones are complementary strategies that, when combined, may have substantial impact on TB epidemics in Africa.