Lung Cancer Presents at a Younger Age and Is Less Likely to be Curable in People Living with HIV.

INTRODUCTION: Globally, lung cancer remains the leading cause of malignancy-related death in men and women. There is increasing evidence that the risk for lung cancer in people living with human immunodeficiency virus (PLHIV) is higher than that of the general population. Given the high burden of PLHIV and lung cancer in Southern Africa, we aimed to compare the characteristics of PLHIV and HIV-negative lung cancer patients with regards to demographics, cell type, performance status, and tumour stage at presentation. METHODS: All patients who presented to a large tertiary hospital over a 7-year period with a confirmed tissue diagnosis of primary lung cancer were included in a prospective registry. The patient demographics, HIV status, as well as the patients' performance status according to the Eastern Cooperative Oncology Group (ECOG) were documented. RESULTS: The cohort consisted of 1,805 patients (mean age 60.0 years) of which 1,129 were male. In total, 133 were PLHIV and 1,292 were confirmed HIV-negative, while the remaining were categorised as HIV-unknown. PLHIV with lung cancer were found to be younger than the HIV-negative group (mean [±SD] 54.6 [9.3] versus 60.3 [10.1], p < 0.001). Notably, not a single PLHIV was diagnosed with resectable non-small cell lung cancer (NSCLC), and only 7 of 133 (6.5%) had potentially curable disease NSCLC (up to stage IIIB) compared to 240 of 1292 HIV-negative patients (27.7%, p < 0.001). CONCLUSION: PLHIV with lung cancer were diagnosed at a significantly younger age and were significantly less likely to have curable NSCLC at presentation.

A practical approach to the diagnosis and management of malignant pleural effusions in resource-constrained settings.

No pleural intervention in a patient with confirmed malignant pleural effusion (MPE) prolongs life, but even the recommended interventions for diagnosis and palliation can be costly and therefore unavailable in large parts of the world. However, there is good evidence to guide clinicians working in low- and middle-income countries on the most cost-effective and clinically effective strategies for the diagnosis and management of MPE. Transthoracic ultrasound-guided closed pleural biopsy is a safe method of pleural biopsy with a diagnostic yield approaching that of thoracoscopy. With the use of pleural fluid cytology and ultrasound-guided biopsy, ≥90% of cases can be diagnosed. Cases with an associated mass lesion are best suited to an ultrasound-guided fine needle aspiration with/without core needle biopsy. Those with diffuse pleural thickening and/or nodularity should have an Abrams needle (<1 cm thickening) or core needle (≥1 cm thickening) biopsy of the area of interest. Those with insignificant pleural thickening should have an ultrasound-guided Abrams needle biopsy close to the diaphragm. The goals of management are to alleviate dyspnoea, prevent re-accumulation of the pleural effusion and minimise re-admissions to hospital. As the most cost-effective strategy, we suggest early use of indwelling pleural catheters with daily drainage for 14 days, followed by talc pleurodesis if the lung expands. The insertion of an intercostal drain with talc slurry is an alternative strategy which is noninferior to thoracoscopy with talc poudrage. Educational aims: To provide clinicians practising in resource-constrained settings with a practical evidence-based approach to the diagnosis and management of malignant pleural effusions.To explain how to perform an ultrasound-guided closed pleural biopsy.To explain the cost-effective use of indwelling pleural catheters.

Clinical characteristics of chylothorax: results from the International Collaborative Effusion database.

Background: Chylothorax is an uncommon medical condition for which limited data are available regarding the contemporary aetiology, management and outcomes. The goal of this study was to better define these poorly characterised features. Methods: The medical records of adult patients diagnosed with chylothorax at 12 centres across Europe, America and South Africa from 2009-2021 were retrospectively reviewed. Descriptive and inferential statistics were performed. Results: 77 patients (median age 69 years, male to female ratio 1.5) were included. Subacute dyspnoea was the most typical presenting symptom (66%). The commonest cause of chylothorax was malignancy (68.8%), with lymphoma accounting for 62% of these cases. Other aetiologies were trauma (13%), inflammatory/miscellaneous conditions (11.7%) and idiopathic cases (6.5%). At the initial thoracentesis, the pleural fluid appeared milky in 73%, was exudative in 89% and exhibited triglyceride concentrations >100 mg·dL-1 in 88%. Lymphangiography/lymphoscintigraphy were rarely ordered (3%), and demonstration of chylomicrons in pleural fluid was never ascertained. 67% of patients required interventional pleural procedures. Dietary measures were infrequently followed (36%). No patient underwent thoracic duct ligation or embolisation. Morbidity included infections (18%), and thrombosis in malignant aetiologies (16%). The 1-year mortality was 47%. Pleural fluid protein >3.5 mg·dL-1 (sub-distribution hazard ratio (SHR) 4.346) or lactate dehydrogenase <500 U·L-1 (SHR 10.21) increased the likelihood of effusion resolution. Pleural fluid protein ≤3.5 mg·dL-1 (HR 4.047), bilateral effusions (HR 2.749) and a history of respiratory disease (HR 2.428) negatively influenced survival. Conclusion: Chylothoraces have a poor prognosis and most require pleural interventions. Despite the standard recommendations, lymphatic imaging is seldom used, nor are dietary restrictions followed.

Immunologic and vascular biomarkers of mortality in critical COVID-19 in a South African cohort.

Introduction: Biomarkers predicting mortality among critical Coronavirus disease 2019 (COVID-19) patients provide insight into the underlying pathophysiology of fatal disease and assist with triaging of cases in overburdened settings. However, data describing these biomarkers in Sub-Saharan African populations are sparse. Methods: We collected serum samples and corresponding clinical data from 87 patients with critical COVID-19 on day 1 of admission to the intensive care unit (ICU) of a tertiary hospital in Cape Town, South Africa, during the second wave of the COVID-19 pandemic. A second sample from the same patients was collected on day 7 of ICU admission. Patients were followed up until in-hospital death or hospital discharge. A custom-designed 52 biomarker panel was performed on the Luminex® platform. Data were analyzed for any association between biomarkers and mortality based on pre-determined functional groups, and individual analytes. Results: Of 87 patients, 55 (63.2%) died and 32 (36.8%) survived. We found a dysregulated cytokine response in patients who died, with elevated levels of type-1 and type-2 cytokines, chemokines, and acute phase reactants, as well as reduced levels of regulatory T cell cytokines. Interleukin (IL)-15 and IL-18 were elevated in those who died, and levels reduced over time in those who survived. Procalcitonin (PCT), C-reactive protein, Endothelin-1 and vascular cell adhesion molecule-1 were elevated in those who died. Discussion: These results show the pattern of dysregulation in critical COVID-19 in a Sub-Saharan African cohort. They suggest that fatal COVID-19 involved excessive activation of cytotoxic cells and the NLRP3 (nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3) inflammasome. Furthermore, superinfection and endothelial dysfunction with thrombosis might have contributed to mortality. HIV infection did not affect the outcome. A clinically relevant biosignature including PCT, pH and lymphocyte percentage on differential count, had an 84.8% sensitivity for mortality, and outperformed the Luminex-derived biosignature.

Rapidly progressive respiratory failure due to antisynthetase syndrome related interstitial lung disease.

A 65-year-old female was admitted with rapidly progressive respiratory failure requiring intubation and mechanical ventilation. She was considered to have an infective exacerbation of underlying interstitial lung disease (ILD). She improved on antibiotics, but the interstitial process progressed rapidly, and she could not be weaned. An antimyositis antibody panel yielded a strongly positive anti-Jo-1 and anti-Ro 52. A diagnosis of antisynthetase syndrome (ASS) associated ILD, a very rare disease with high mortality, was made. She was managed with high-dose corticosteroids and intravenous immunoglobulin therapy and was eventually liberated from mechanical ventilation. This case highlights the importance of considering ASS in an otherwise unexplained rapidly progressive ILD requiring mechanical ventilation.

Fatal sequelae of hydrogen sulphide poisoning.

Hydrogen sulphide (H2S) is a toxic, colourless gas abundantly present at waste plants and sewers due to the presence of anaerobic forming organisms. Hazardous exposure via accidental, intentional or occupational contact results in endothelium disruption, cellular instability, decreased respiratory functional capacity and cardiovascular compromise with a rapidly fatal clinical course. Clinical manifestations are variable depending on the level of exposure with moderate or heavy exposure associated with rapid fatality. Respiratory manifestations remain the primary reason for admission to critical care facilities. We describe a case of a 30-year-old sewer worker with a history of heavy accidental occupational exposure of inhaled H2S admitted with acute respiratory distress syndrome and a rapid respiratory decline ultimately leading to death.

Investigation and outcomes in patients with nonspecific pleuritis: results from the International Collaborative Effusion database.

Introduction: We present findings from the International Collaborative Effusion database, a European Respiratory Society clinical research collaboration. Nonspecific pleuritis (NSP) is a broad term that describes chronic pleural inflammation. Various aetiologies lead to NSP, which poses a diagnostic challenge for clinicians. A significant proportion of patients with this finding eventually develop a malignant diagnosis. Methods: 12 sites across nine countries contributed anonymised data on 187 patients. 175 records were suitable for analysis. Results: The commonest aetiology for NSP was recorded as idiopathic (80 out of 175, 44%). This was followed by pleural infection (15%), benign asbestos disease (12%), malignancy (6%) and cardiac failure (6%). The malignant diagnoses were predominantly mesothelioma (six out of 175, 3.4%) and lung adenocarcinoma (four out of 175, 2.3%). The median time to malignant diagnosis was 12.2 months (range 0.8-32 months). There was a signal towards greater asbestos exposure in the malignant NSP group compared to the benign group (0.63 versus 0.27, p=0.07). Neither recurrence of effusion requiring further therapeutic intervention nor initial biopsy approach were associated with a false-negative biopsy. A computed tomography finding of a mass lesion was the only imaging feature to demonstrate a significant association (0.18 versus 0.01, p=0.02), although sonographic pleural thickening also suggested an association (0.27 versus 0.09, p=0.09). Discussion: This is the first multicentre study of NSP and its associated outcomes. While some of our findings are reflected by the established body of literature, other findings have highlighted important areas for future research, not previously studied in NSP.

Clinical features and outcomes of COVID-19 admissions in a population with a high prevalence of HIV and tuberculosis: a multicentre cohort study.

BACKGROUND: There is still a paucity of evidence on the outcomes of coronavirus disease 2019 (COVID-19) among people living with human immunodeficiency virus (PWH) and those co-infected with tuberculosis (TB), particularly in areas where these conditions are common. We describe the clinical features, laboratory findings and outcome of hospitalised PWH and human immunodeficiency virus (HIV)-uninfected COVID-19 patients as well as those co-infected with tuberculosis (TB). METHODS: We conducted a multicentre cohort study across three hospitals in Cape Town, South Africa. All adults requiring hospitalisation with confirmed COVID-19 pneumonia from March to July 2020 were analysed. RESULTS: PWH comprised 270 (19%) of 1434 admissions. There were 47 patients with active tuberculosis (3.3%), of whom 29 (62%) were PWH. Three-hundred and seventy-three patients (26%) died. The mortality in PWH (n = 71, 26%) and HIV-uninfected patients (n = 296, 25%) was comparable. In patients with TB, PWH had a higher mortality than HIV-uninfected patients (n = 11, 38% vs n = 3, 20%; p = 0.001). In multivariable survival analysis a higher risk of death was associated with older age (Adjusted Hazard Ratio (AHR) 1.03 95%CI 1.02-1.03, p < 0.001), male sex (AHR1.38 (95%CI 1.12-1.72, p = 0.003) and being "overweight or obese" (AHR 1.30 95%CI 1.03-1.61 p = 0.024). HIV (AHR 1.28 95%CI 0.95-1.72, p 0.11) and active TB (AHR 1.50 95%CI 0.84-2.67, p = 0.17) were not independently associated with increased risk of COVID-19 death. Risk factors for inpatient mortality in PWH included CD4 cell count < 200 cells/mm3, higher admission oxygen requirements, absolute white cell counts, neutrophil/lymphocyte ratios, C-reactive protein, and creatinine levels. CONCLUSION: In a population with high prevalence of HIV and TB, being overweight/obese was associated with increased risk of mortality in COVID-19 hospital admissions, emphasising the need for public health interventions in this patient population.

Diagnosing Tuberculosis: What Do New Technologies Allow Us to (Not) Do?

New tuberculosis (TB) diagnostics are at a crossroads: their development, evaluation, and implementation is severely damaged by resource diversion due to COVID-19. Yet several technologies, especially those with potential for non-invasive non-sputum-based testing, hold promise for efficiently triaging and rapidly confirming TB near point-of-care. Such tests are, however, progressing through the pipeline slowly and will take years to reach patients and health workers. Compellingly, such tests will create new opportunities for difficult-to-diagnose populations, including primary care attendees (all-comers in high burden settings irrespective of reason for presentation) and community members (with early stage disease or risk factors like HIV), many of whom cannot easily produce sputum. Critically, all upcoming technologies have limitations that implementers and health workers need to be cognizant of to ensure optimal deployment without undermining confidence in a technology that still offers improvements over the status quo. In this state-of-the-art review, we critically appraise such technologies for active pulmonary TB diagnosis. We highlight strengths, limitations, outstanding research questions, and how current and future tests could be used in the presence of these limitations and uncertainties. Among triage tests, CRP (for which commercial near point-of-care devices exist) and computer-aided detection software with digital chest X-ray hold promise, together with late-stage blood-based assays that detect host and/or microbial biomarkers; however, aside from a handful of prototypes, the latter category has a shortage of promising late-stage alternatives. Furthermore, positive results from new triage tests may have utility in people without TB; however, their utility for informing diagnostic pathways for other diseases is under-researched (most sick people tested for TB do not have TB). For confirmatory tests, few true point-of-care options will be available soon; however, combining novel approaches like tongue swabs with established tests like Ultra have short-term promise but first require optimizations to specimen collection and processing procedures. Concerningly, no technologies yet have compelling evidence of meeting the World Health Organization optimal target product profile performance criteria, especially for important operational criteria crucial for field deployment. This is alarming as the target product profile criteria are themselves almost a decade old and require urgent revision, especially to cater for technologies made prominent by the COVID-19 diagnostic response (e.g., at-home testing and connectivity solutions). Throughout the review, we underscore the importance of how target populations and settings affect test performance and how the criteria by which these tests should be judged vary by use case, including in active case finding. Lastly, we advocate for health workers and researchers to themselves be vocal proponents of the uptake of both new tests and those - already available tests that remain suboptimally utilized.

Targeted Gene Expression Profiling of Human Myeloid Cells From Blood and Lung Compartments of Patients With Tuberculosis and Other Lung Diseases.

Myeloid-derived suppressor cells (MDSC) have been identified in the peripheral blood and granulomas of patients with active TB disease, but their phenotype-, function-, and immunosuppressive mechanism- spectrum remains unclear. Importantly, the frequency and signaling pathways of MDSC at the site of disease is unknown with no indication how this compares to MDSC identified in peripheral blood or to those of related myeloid counterparts such as alveolar macrophages and monocytes. Most phenotypic and functional markers have been described in oncological studies but have not yet been validated in TB. Using a panel of 43 genes selected from pathways previously shown to contribute to tumor-derived MDSC, we set out to evaluate if the expression of these additional functional markers and properties may also be relevant to TB-derived MDSC. Differential expression was investigated between MDSC, alveolar macrophages and monocytes enriched from bronchoalveolar lavage fluid and peripheral blood of patients with active TB, patients with other lung diseases (OLD). Results demonstrated that anatomical compartments may drive compartment-specific immunological responses and subsequent MDSC immunosuppressive functions, demonstrated by the observation that MDSC and/or monocytes from PB alone can discriminate, via hierarchical clustering, between patients with active TB disease and OLD. Our data show that the gene expression patterns of MDSC in peripheral blood and bronchoalveolar lavage fluid do not cluster according to disease states (TB vs OLD). This suggests that MDSC from TB patients may display similar gene expression profiles to those found for MDSC in cancer, but this needs to be validated in a larger cohort. These are important observations for TB research and may provide direction for future studies aimed at repurposing and validating cancer immunotherapies for use in TB.

Lung Cancer Screening Considerations During Respiratory Infection Outbreaks, Epidemics or Pandemics: An International Association for the Study of Lung Cancer Early Detection and Screening Committee Report.

After the results of two large, randomized trials, the global implementation of lung cancer screening is of utmost importance. However, coronavirus disease 2019 infections occurring at heightened levels during the current global pandemic and also other respiratory infections can influence scan interpretation and screening safety and uptake. Several respiratory infections can lead to lesions that mimic malignant nodules and other imaging changes suggesting malignancy, leading to an increased level of follow-up procedures or even invasive diagnostic procedures. In periods of increased rates of respiratory infections from severe acute respiratory syndrome coronavirus 2 and others, there is also a risk of transmission of these infections to the health care providers, the screenees, and patients. This became evident with the severe acute respiratory syndrome coronavirus 2 pandemic that led to a temporary global stoppage of lung cancer and other cancer screening programs. Data on the optimal management of these situations are not available. The pandemic is still ongoing and further periods of increased respiratory infections will come, in which practical guidance would be helpful. The aims of this report were: (1) to summarize the data available for possible false-positive results owing to respiratory infections; (2) to evaluate the safety concerns for screening during times of increased respiratory infections, especially during a regional outbreak or an epidemic or pandemic event; (3) to provide guidance on these situations; and (4) to stimulate research and discussions about these scenarios.

Autologous Blood Patch Pleurodesis for the Management of a Persistent Air Leak after Secondary Spontaneous Pneumothorax.

Patients with secondary spontaneous pneumothorax (SSP) complicated by persistent air leak (PAL) and who are poor surgical candidates have limited treatment options. This case series explored autologous blood patch pleurodesis as a possible cost-effective management option. A total of 46 episodes of SSP with PAL were included. The procedure was successful in 33 (71.7%). Of these, 17 (51.5%) resolved within 1 day. The mean duration of intercostal drainage prior to the blood patch was 22 days in the successful group. Pneumothoraces with incomplete lung re-expansion at the time of procedure were successful in 20 of 30 (66.7%). Only human immunodeficiency virus infection was associated with failure (p = 0.03). Adverse events included transient fever (n = 3) that resolved spontaneously, and empyema (n = 3) which were successfully managed with antibiotics and pigtail drainage. We conclude that a large proportion of patients with SSP complicated by PAL who are unfit for surgery may be liberated from intercostal drainage by an autologous blood patch pleurodesis, with minimal adverse effects.

Pleural Tuberculosis.

Pleural tuberculosis (TB) is common and often follows a benign course but may result in serious long-term morbidity. Diagnosis is challenging because of the paucibacillary nature of the condition. Advances in Mycobacterium culture media and PCR-based techniques have increased the yield from mycobacteriologic tests. Surrogate biomarkers perform well in diagnostic accuracy studies but must be interpreted in the context of the pretest probability in the individual patient. Confirming the diagnosis often requires biopsy, which may be acquired through thoracoscopy or image-guided closed pleural biopsy. Treatment is standard anti-TB therapy, with optional drainage and intrapleural fibrinolytics or surgery in complicated cases.

Opportunities to enhance antibiotic stewardship: colistin use and outcomes in a low-resource setting.

BACKGROUND: Colistin use is increasing with the rise in MDR Gram-negative infections globally. Effective antibiotic stewardship is essential to preserve this antibiotic of last resort. OBJECTIVES: This study investigated stewardship and safety errors related to colistin use to identify opportunities for improvement. PATIENTS AND METHODS: A prospective descriptive study involving all patients 13 years and older treated with colistin at a tertiary hospital in Cape Town, South Africa, between August 2018 and June 2019. We collected clinical, laboratory and outcome data and assessed provided treatment for stewardship and safety errors. RESULTS: We included 44 patients. Treatment errors were identified for 34 (77%) patients (median = 1), most commonly inadequate monitoring of renal function (N = 16, 32%). We also identified no rational indication for colistin (N = 9, 20%), loading dose error (N = 12, 27%); maintenance dose error (N = 10, 23%); no prior culture (N = 11, 25%); and failure to de-escalate (2 of 9) or adjust dose to changes in renal function (6 of 15). All cause in-hospital mortality was 47%. Amongst survivors, median ICU stay was 6 days and hospital stay more than 30 days. Eight (18%) patients developed renal injury or failure during treatment. Three (7%) patients in this study were found to have colistin-resistant organisms including two prior to colistin exposure. CONCLUSIONS: This study has identified opportunities to enhance colistin stewardship and improve efficacy and safety of prescription. The appearance of colistin-resistant organisms reinforces the urgent need to ensure effective and appropriate use of colistin.

Establishment of a Patient-Derived, Magnetic Levitation-Based, Three-Dimensional Spheroid Granuloma Model for Human Tuberculosis.

Tuberculous granulomas that develop in response to Mycobacterium tuberculosis (M. tuberculosis) infection are highly dynamic entities shaped by the host immune response and disease kinetics. Within this microenvironment, immune cell recruitment, polarization, and activation are driven not only by coexisting cell types and multicellular interactions but also by M. tuberculosis-mediated changes involving metabolic heterogeneity, epigenetic reprogramming, and rewiring of the transcriptional landscape of host cells. There is an increased appreciation of the in vivo complexity, versatility, and heterogeneity of the cellular compartment that constitutes the tuberculosis (TB) granuloma and the difficulty in translating findings from animal models to human disease. Here, we describe a novel biomimetic in vitro three-dimensional (3D) human lung spheroid granuloma model, resembling early "innate" and "adaptive" stages of the TB granuloma spectrum, and present results of histological architecture, host transcriptional characterization, mycobacteriological features, cytokine profiles, and spatial distribution of key immune cells. A range of manipulations of immune cell populations in these spheroid granulomas will allow the study of host/pathogen pathways involved in the outcome of infection, as well as pharmacological interventions. IMPORTANCE TB is a highly infectious disease, with granulomas as its hallmark. Granulomas play an important role in the control of M. tuberculosis infection and as such are crucial indicators for our understanding of host resistance to TB. Correlates of risk and protection to M. tuberculosis are still elusive, and the granuloma provides the perfect environment in which to study the immune response to infection and broaden our understanding thereof; however, human granulomas are difficult to obtain, and animal models are costly and do not always faithfully mimic human immunity. In fact, most TB research is conducted in vitro on immortalized or primary immune cells and cultured in two dimensions on flat, rigid plastic, which does not reflect in vivo characteristics. We have therefore conceived a 3D, human in vitro spheroid granuloma model which allows researchers to study features of granuloma-forming diseases in a 3D structural environment resembling in vivo granuloma architecture and cellular orientation.

Relative Sparing of the Left Upper Zone on Chest Radiography in Severe COVID-19 Pneumonia.

The radiological findings of COVID-19 are well-described, including its evolution. In an earlier report of admission chest radiographs of patients with COVID-19, we anecdotally noted relative sparing of the left upper zone (LUZ). We subsequently aimed to describe the main chest radiograph findings in another cohort, focusing on zonal predominance. The admission chest radiographs of 111 patients with CO-VID-19 pneumonia requiring intensive care admission were reviewed by 2 thoracic radiologists and categorized according to the predominant pattern into either ground-glass opacities (GGOs), alveolar infiltrates and/or consolidation, or reticular and/or nodular infiltrates or an equal combination of both, and the extent of disease involvement of each of the zones using a modified Radiologic Assessment of Lung Edema (RALE) score. Parenchymal changes were detected in all. In total, 106 radiographs showed GGOs, alveolar infiltrates, and/or consolidation, and 5 had a combination of reticular/nodular infiltrates as well as GGOs, alveolar infiltrates, and/or consolidation. The LUZ had a significant lower grading score than the right upper zone: 1 versus 2 (p < 0.001). Likewise, the upper zones had a significant lower score than the mid and lower zones (p < 0.001). Our findings confirmed the relative sparing of the LUZ in severe COVID-19 pneumonia.

The diagnostic challenge of pneumocystis pneumonia and COVID-19 co-infection in HIV.

Coronavirus disease 2019 (COVID-19) and pneumocystis pneumonia (PCP) share many overlapping features and may be clinically indistinguishable on initial presentation in people living with HIV. We present the case of co-infection with COVID-19 and PCP in a patient with progressive respiratory failure admitted to our intensive care unit where the dominant disease was uncertain. This case highlights the difficulty in differentiating between the two diseases, especially in a high HIV prevalence setting where PCP is frequently diagnosed using case definitions and clinical experience due to limited access to bronchoscopy, appropriate laboratory testing, and computed tomography scans. In addition, diagnostic testing may yield false-negative results in both diseases, and clinician awareness to the overlap and pitfalls is essential if COVID-19 becomes endemic in such settings.

The Utility of Pleural Fluid Lactate Dehydrogenase to Adenosine Deaminase Ratio in Pleural Tuberculosis.

In high-burden settings, the diagnosis of pleural tuberculosis (TB) is frequently inferred in patients who present with lymphocyte predominant exudative effusions and high adenosine deaminase (ADA) levels. Two recent small retrospective studies suggested that the lactate dehydrogenase (LDH)/ADA ratio is significantly lower in TB than in non-TB pleural effusions and that the LDH/ADA ratio may be useful in differentiating pleural TB from other pleural exudates. We compared the pleural LDH/ADA ratios, ADA levels, and lymphocyte predominance of a prospectively collected cohort of patients with proven pleural TB (n = 160) to those with a definitive alternative diagnosis (n = 68). The mean pleural fluid LDH/ADA ratio was lower in patients with pleural TB than alternative diagnoses (6.2 vs. 34.3, p < 0.001). The area under the receiver operating characteristic curve was 0.92 (p < 0.001) for LDH/ADA ratio and 0.88 (p < 0.001) for an ADA ≥40 U/L alone. A ratio of ≤12.5 had the best overall diagnostic efficiency, while a ratio of ≤10 had a specificity of 90% and a positive predictive value of 95%, with a sensitivity of 78%, making it a clinically useful "rule in" value for pleural TB in high incidence settings. When comparing the LDH/ADA ratio to an ADA level ≥40 U/L in the presence of a lymphocyte predominant effusion, the latter performed better. When lymphocyte values are unavailable, our data suggest that the LDH/ADA ratio is valuable in distinguishing TB effusions from other pleural exudates.