Background Tuberculosis (TB) diagnosis in the UK is impacted by delay and suboptimal culture-based microbiological confirmation rates due to the high prevalence of paucibacillary disease. We examine the real-world clinical utility of Xpert MTB/RIF Ultra (Xpert-Ultra) as a diagnostic test and biomarker of transmissible infection in a UK TB service. Methods Clinical specimens from suspected TB cases triple tested (smear microscopy, mycobacterial culture and Xpert-Ultra) at University Hospitals of Leicester NHS Trust (1 March 2018-28 February 2019) were retrospectively analysed. Diagnostic sensitivity and specificity were calculated using positive MTB culture and clinical TB diagnosis as reference standards. The QuantiFERON (QFT) positive proportion of pulmonary TB (PTB) contacts was used as a metric of transmitted infection to evaluate Xpert-Ultra and smear grade as markers of infectiousness. Results 251 samples (188 respiratory) from 231 patients (86 TB) were analysed. Compared with microscopy, Xpert-Ultra had higher diagnostic sensitivity (24.7% vs 78.7%, p<0.001) and comparable specificity (97.5% vs 99.4%). Xpert-Ultra and culture had comparable sensitivity (78.7% vs 71.9%) and specificity (99.4% vs 100.0%). Incorporating Xpert-Ultra with culture increased microbiologically verified diagnosis to 91.7% for PTB and 75.9% for extrapulmonary TB, compared with 85.0% and 44.8%, using culture alone. In PTB, both smear and Xpert-Ultra grade were positively associated with the proportion of contacts testing QFT positive. However, Xpert-Ultra had a higher negative predictive value than smear (QFT-positive contacts 6.7% vs 17.7%). Conclusion In low-TB-burden settings, systematic adoption of Xpert-Ultra for clinical assessment of suspected TB can improve the proportion of microbiologically verified diagnoses and improve the stratification of transmission risk.

Objectives: We investigated whether quantifying the serial QuantiFERON-TB Gold (QFT) response improves tuberculosis (TB) risk stratification in pulmonary TB (PTB) contacts. Methods: A total of 297 untreated adult household PTB contacts, QFT tested at baseline and 3 months after index notification, were prospectively observed (median 1460 days). Normal variance of serial QFT responses was established in 46 extrapulmonary TB contacts. This informed categorisation of the response in QFT-positive PTB contacts as converters, persistently QFT-positive with significant increase (PPincrease), and without significant increase (PPno-increase). Results: In total, eight co-prevalent TB (disease ≤3 months after index notification) and 12 incident TB (>3 months after index notification) cases were diagnosed. Genetic linkage to the index strain was confirmed in all culture-positive progressors. The cumulative 2-year incident TB risk in QFT-positive contacts was 8.4% (95% confidence interval, 3.0-13.6%); stratifying by serial QFT response, significantly higher risk was observed in QFT converters (28%), compared with PPno-increase (4.8%) and PPincrease (3.7%). Converters were characterised by exposure to index cases with a shorter interval from symptom onset to diagnosis (median reduction 50.0 days, P = 0.013). Conclusions: QFT conversion, rather than quantitative changes of a persistently positive serial QFT response, is associated with greater TB risk and exposure to rapidly progressive TB.

Background: Screening and treatment for latent tuberculosis infection (LTBI) are key for TB control. In the UK, the National Institute for Health and Care Excellence (NICE) and the British HIV Association (BHIVA) give conflicting guidance on which groups of people with HIV (PWH) should be screened, and previous national analysis demonstrated heterogeneity in how guidance is applied. There is an urgent need for a firmer clinical effectiveness evidence base on which to build screening policy. Methods: We conducted a systematic, programmatic LTBI-screening intervention for all PWH receiving care in Leicester, UK. We compared yields (percentage IGRA positive) and number of tests required when applying the NICE and BHIVA testing strategies, as well as strategies targeting screening by TB incidence in patients’ countries of birth. Results: Of 1053 PWH tested, 118 were IGRA-positive (11.2%). Positivity was associated with higher TB incidence in country-of-birth [adjusted odds ratio, 50–149 cases compared with <50 cases/100 000: 11.6; 95% confidence interval (CI) 4.79–28.10)]. There was high testing uptake (1053/1069, 98.5%). Appropriate chemoprophylaxis was commenced in 100 of 117 (85.5%) patients diagnosed with LTBI, of whom 96 of 100 (96.0%) completed treatment. Delivering targeted testing to PWH from countries with TB incidence greater than 150 per 100 000 population or any sub-Saharan African country, would have correctly identified 89.8% of all LTBI cases while cutting tests required by 46.1% compared with NICE guidance, performing as well as BHIVA 2018 guidance. Conclusion: Targeting screening to higher risk PWH increases yield and reduces the number requiring testing. Our proposed ‘PWH-LTBI streamlined guidance’ offers a simplified approach, with the potential to improve national LTBI-screening implementation.

Background People living with HIV (PLWH) are at increased risk of re-activation of latent tuberculosis infection (LTBI). Although UK and international guidelines identify this group as a priority for LTBI screening and treatment, data on attitudes of PLWH to this policy recommendation are lacking. Methods A five-point, Likert-style questionnaire was administered to PLWH to assess views and intentions towards accepting LTBI screening and treatment. Subsequent interferon-γ release assay (IGRA) testing was offered, and chemoprophylaxis if required. Influencing demographic and psychological associations with planned, and actual, testing and treatment uptake were assessed using multivariable logistic regression. Results 444 out of 716 (62%) patients responded. 417 out of 437 (95.4%) expressed intention to accept LTBI testing. The only significant association was the perceived importance of testing to the individual (adjusted odds ratio (aOR) 8.98, 95% CI 2.55–31.67). 390 out of 393 (99.2%) accepted appropriate IGRA screening; 41 out of 390 (10.5%) were positive. 397 out of 431 (92.1%) expressed intention to accept chemoprophylaxis, associated with perceived importance of treatment (aOR 3.52, 95% CI 1.46–8.51), a desire to have treatment for LTBI (aOR 1.77, 95% CI 0.99–3.15) and confidence in taking treatment (aOR 3.77, 95% CI 1.84–7.72). Of those offered chemoprophylaxis, 36 out of 37 (97.3%) accepted and 34 out of 36 (94.4%) completed treatment. There were no correlates with actual screening acceptance. Conclusions LTBI is common amongst PLWH, highlighting the importance of robust screening and treatment programmes. This study shows that screening and treatment for LTBI is highly acceptable to PLWH and provides strong, objective evidence for policy-makers developing guidelines in this cohort.

Tuberculosis (TB) killed 1.5 million people in 2020 and affects every country. The extent to which the natural genetic diversity of Mycobacterium tuberculosis influences disease manifestation at both the individual and epidemiological levels remains poorly understood.

Background: Screening and treatment for latent tuberculosis infection (LTBI) are recognised as key for tuberculosis control, being central to WHO’s End TB Strategy. In the UK, the National Institute for Health and Care Excellence (NICE) and British HIV Association (BHIVA) give conflicting guidance on which groups of people living with HIV (PLWH) should be screened, and previous national analysis demonstrated heterogeneity in how guidance is applied. There is an urgent need for a firmer clinical effectiveness evidence base on which to build screening policy.Methods: We conducted a systematic, programmatic LTBI screening intervention using interferon gamma release assay (IGRA) tests for all PLWH receiving care in Leicester, UK. We compared yields (percentage IGRA positive) and number of tests required when applying the NICE and BHIVA testing strategies, as well as strategies targeting screening by tuberculosis incidence in patients’ countries of birth.Findings: Of 1175 PLWH tested, 142 were IGRA-positive (12·1%), with IGRA-positivity associated with higher tuberculosis incidence in country-of-birth (adjusted odds ratio, incidence 150-249/100,000: 7·25 (95%CI 4·06–12·95)). There was high uptake of testing (1175/1191, 98·7%), LTBI chemoprophylaxis commencement (121/141, 85·8%) and completion (116/121, 95·9%). Proposed ‘PLWH-LTBI streamlined guidance’, targeting testing to PLWH born in countries with TB incidence >150/100,000 or any sub-Saharan African country, would have correctly identified 88·7% of all LTBI cases while cutting tests required by 42·6% compared to NICE guidance (screening all PLWH), performing as well as BHIVA 2018 guidance.Interpretation: LTBI screening and treatment is feasible and achievable for PLWH in the UK. Targeting screening to higher-risk PLWH increases yield and reduces screening costs, at the expense of missing some LTBI cases. Our proposed ‘PLWH-LTBI streamlined guidance’ based on country-of-birth performs as well as current BHIVA guidance and offers a simplified approach, with the hope of improving national screening uptake.Funding: NIHR, MRC, Wellcome TrustDeclaration of Interest: MP received grants and personal fees from Gilead Sciences and personal fees from QIAGEN, outside the submitted work. All other authors have nothing to declare.

BackgroundWith the onset of the COVID-19 pandemic in 2020, hospital clinical teams have realised that there is a need for a rapid, accurate testing facility that will allow them to move patients quickly into isolation rooms or specific COVID-19 cohort wards as soon as possible after admission.MethodsStarting from July 2020, PCR-based test platforms, which could test 4–8 samples in parallel with turnaround (sample-to-result) times of 50–80 min, were placed in a satellite laboratory. This laboratory was on the same floor and within walking distance to the acute respiratory admissions ward. It was staffed by a team of three mid-Band 4 staff that split a 0700–2200 h-work day, 7 days a week, with 2 senior supervisors. Urgent sample testing was decided upon by the clinical teams and requested by phone. The test results were entered manually in real-time as they became available, and sent electronically to the requesting ward teams.ResultsThe daily/monthly PCR positive test numbers approximately followed the local and national UK trend in COVID-19 case numbers, with the daily case numbers being reflective of the November and December 2020 surges. Test results were used to rapidly segregate positive patients into dedicated COVID-19 ward areas to minimise risk of potential nosocomial transmission in crowded waiting areas. Testing capacity was sufficient to include cases with uncertain diagnosis likely to require hospital admission. Following completion of other admission processes, based on these rapid test results, patients were allocated to dedicated COVID-19 positive or negative cohort wards.ConclusionsThis rapid testing facility reduced unnecessary ‘length-of-stay’ in a busy acute respiratory ward. In the current absence of a treatment for mild-to-moderate COVID-19, on which patients could be discharged home to complete, the rapid test facility has become a successful aid to patient flow and reduced exposure and nosocomial transmission.

Background Migration is a major global driver of population change. Certain migrants may be at increased risk of infectious diseases, including tuberculosis (TB), HIV, hepatitis B and hepatitis C, and have poorer outcomes. Early diagnosis and management of these infections can reduce morbidity, mortality and onward transmission and is supported by national guidelines. To date, screening initiatives have been sporadic and focused on individual diseases; systematic routine testing of migrant groups for multiple infections is rarely undertaken and its impact is unknown. We describe the protocol for the evaluation of acceptability, effectiveness and cost-effectiveness of an integrated approach to screening migrants for a range of infectious diseases in primary care. Methods and analysis We will conduct a mixed-methods study which includes an observational cohort with interrupted time-series analysis before and after the introduction of routine screening of migrants for infectious diseases (latent TB, HIV, hepatitis B and hepatitis C) when first registering with primary care within Leicester, UK. We will assess trends in the monthly number and rate of testing and diagnosis for latent TB, HIV, hepatitis B and hepatitis C to determine the effect of the policy change using segmented regression analyses at monthly time-points. Concurrently, we will undertake an integrated qualitative sub-study to understand the views of migrants and healthcare professionals to the new testing policy in primary care. Finally, we will evaluate the cost-effectiveness of combined infection testing for migrants in primary care. Ethics and dissemination The study has received HRA and NHS approvals for both the interrupted time-series analysis (16/SC/0127) and the qualitative sub-study (16/EM/0159). For the interrupted time-series analysis we will only use fully anonymised data. For the qualitative sub-study, we will gain written, informed, consent. Dissemination of the results will be through local and national meetings/conferences as well as publications in peer-reviewed journals.

ABSTRACT Tuberculous sputum contains multiple Mycobacterium tuberculosis populations with different requirements for isolation in vitro . These include cells that form colonies on solid media (plateable M. tuberculosis ), cells requiring standard liquid medium for growth (nonplateable M. tuberculosis ), and cells requiring supplementation of liquid medium with culture supernatant (SN) for growth (SN-dependent M. tuberculosis ). Here, we describe protocols for the cryopreservation and direct assessment of antimicrobial tolerance of these M. tuberculosis populations within sputum. Our results show that first-line drugs achieved only modest bactericidal effects on all three populations over 7 days (1 to 2.5 log 10 reductions), and SN-dependent M. tuberculosis was more tolerant to streptomycin and isoniazid than the plateable and nonplateable M. tuberculosis strains. Susceptibility of plateable M. tuberculosis to bactericidal drugs was significantly increased after passage in vitro ; thus, tolerance observed in the sputum samples from the population groups was likely associated with mycobacterial adaptation to the host environment at some time prior to expectoration. Our findings support the use of a simple ex vivo system for testing drug efficacies against mycobacteria that have phenotypically adapted during tuberculosis infection.

BACKGROUND:Potentially pathogenic microorganisms can be detected by quantitative real-time polymerase chain reaction (qPCR) in sputum from patients with COPD, although how this technique relates to culture and clinical measures of disease is unclear. We used cross-sectional and longitudinal data to test the hypotheses that qPCR is a more sensitive measure of bacterial presence and is associated with neutrophilic airway inflammation and adverse clinical outcomes. METHODS:Sputum was collected from 174 stable COPD subjects longitudinally over 12 months. Microbial sampling using culture and qPCR was performed. Spirometry and sputum measures of airway inflammation were assessed. FINDINGS:Sputum was qPCR-positive (>10(6) copies/mL) in 77/152 samples (Haemophilus influenzae [n=52], Moraxella catarrhalis [n=24], Streptococcus pneumoniae [n=19], and Staphylococcus aureus [n=7]). Sputum was culture-positive in 50/174 samples, with 49 out of 50 culture-positive samples having pathogen-specific qPCR bacterial loads >10(6) copies/mL. Samples that had qPCR copy numbers >10(6)/mL, whether culture-positive or not, had increased sputum neutrophil counts. H. influenzae qPCR copy numbers correlated with sputum neutrophil counts (r=0.37, P<0.001), were repeatable within subjects, and were >10(6)/mL three or more times in 19 patients, eight of whom were repeatedly sputum culture-positive. Persistence, whether defined by culture, qPCR, or both, was associated with a higher sputum neutrophil count, lower forced expiratory volume in 1 second (FEV1), and worsened quality of life. INTERPRETATION:qPCR identifies a significant number of patients with potentially bacteria-associated neutrophilic airway inflammation and disease that are not identified by traditional culture-based methods.

Background Although tuberculosis is transmitted by the airborne route, direct information on the natural output of bacilli into air by source cases is very limited. We sought to address this through sampling of expelled aerosols in face masks that were subsequently analyzed for mycobacterial contamination. Methods In series 1, 17 smear microscopy positive patients wore standard surgical face masks once or twice for periods between 10 minutes and 5 hours; mycobacterial contamination was detected using a bacteriophage assay. In series 2, 19 patients with suspected tuberculosis were studied in Leicester UK and 10 patients with at least one positive smear were studied in The Gambia. These subjects wore one FFP30 mask modified to contain a gelatin filter for one hour; this was subsequently analyzed by the Xpert MTB/RIF system. Results In series 1, the bacteriophage assay detected live mycobacteria in 11/17 patients with wearing times between 10 and 120 minutes. Variation was seen in mask positivity and the level of contamination detected in multiple samples from the same patient. Two patients had non-tuberculous mycobacterial infections. In series 2, 13/20 patients with pulmonary tuberculosis produced positive masks and 0/9 patients with extrapulmonary or non-tuberculous diagnoses were mask positive. Overall, 65% of patients with confirmed pulmonary mycobacterial infection gave positive masks and this included 3/6 patients who received diagnostic bronchoalveolar lavages. Conclusion Mask sampling provides a simple means of assessing mycobacterial output in non-sputum expectorant. The approach shows potential for application to the study of airborne transmission and to diagnosis.

BACKGROUND: Relationships between airway inflammation and respiratory potentially pathogenic microorganisms (PPMs) quantified using quantitative polymerase chain reaction (qPCR) in subjects with COPD are unclear. Our aim was to evaluate mediators of airway inflammation and their association with PPMs in subjects with COPD at stable state and during exacerbations. METHODS: Sputum from 120 stable subjects with COPD was analyzed for bacteriology (colony-forming units; total 16S; and qPCR targeting Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae), differential cell counts, and inflammatory mediators using the Meso-Scale Discovery Platform. Subjects were classified as colonized if any PPM was identified above the threshold of detection by qPCR. Symptoms were quantified using the visual analog scale. RESULTS: At stable state, 60% of subjects were qPCR positive for H influenzae, 48% for M catarrhalis, and 28% for S pneumoniae. Elevated sputum concentrations of IL-1β, IL-10, and tumor necrosis factor (TNF)-α were detected in samples qPCR positive for either H influenzae or M catarrhalis. Bacterial loads of H influenzae positively correlated with IL-1β, IL-8, IL-10, TNF-α, and symptoms; and M catarrhalis correlated with IL-10 and TNF-α. H influenzae qPCR bacterial load was an independent predictor of sputum TNF-α and IL-1β. In 55 subjects with paired exacerbation data, qPCR bacterial load fold change at exacerbation in M catarrhalis but not H influenzae correlated to changes in sputum TNF-α and IL-1β concentrations. CONCLUSIONS: At stable state, H influenzae is associated with increased airway inflammation in COPD. The relationship between bacterial load changes of specific pathogens and airway inflammation at exacerbation and recovery warrants further investigation.

Background: Nutritional depletion is an important manifestation of chronic obstructive pulmonary disease (COPD), which has been related to systemic inflammation. It remains unclear to what degree airway inflammation contributes to the presence or progression of nutritional depletion.Objectives: To determine whether airway inflammation and lung bacterial colonization are related to nutritional status or predict progressive weight loss and muscle atrophy in patients with COPD.Methods: Body composition using dual energy X-ray absorptiometry, indices of airway inflammation, and bacterial colonization were measured in 234 COPD patients. Systemic inflammation was assessed from serum C reactive protein (CRP) and circulating total and differential leukocyte counts. Nutritional depletion was defined as a body mass index (BMI) less than 21 kg/m(2) and/or fat-free mass index (FFMI) less than 15 or 17 kg/m(2) in women and men, respectively. FFMI was calculated as the fat-free mass (FFM) corrected for body surface area. Measurements were repeated in 94 patients after a median 16-month follow-up. Regression analysis was used to assess the relationships of weight change and FFM change with indices of bacterial colonization and airway and systemic inflammation.Results: Nutritional depletion occurred in 37% of patients. Lung function was worsened in patients with nutritional depletion compared to those without (forced expiratory volume in 1 second 1.17 L versus 1.41 L, mean difference 0.24, 95% confidence interval 0.10 to 0.38, P < 0.01). There were no differences in airway inflammation and bacterial colonization in patients with and without nutritional depletion. At baseline, BMI correlated positively with serum CRP (r(s) = 0.14, P = 0.04). Change in weight and change in FFM over time could not be predicted from baseline patient characteristics.Conclusion: Nutritional depletion and progressive muscle atrophy are not related to airway inflammation or bacterial colonization. Overspill of pulmonary inflammation is not a key driver of muscle atrophy in COPD.

Background: In COPD bacterial colonisation is associated with a sputum neutrophilia and increased airway inflammation. Quantitative PCR (qPCR) is more sensitive than culture for bacterial detection. Relationships between sputum inflammatory mediators and pathogens quantified by qPCR in stable state are unclear. Methods: Sputum from 66 stable COPD patients was analysed for bacterial load (semi-quantitative culture [colony forming units/ml, CFU], qPCR for Haemophilus influenzae [HI], Streptococcus pneumoniae [SP] and Moraxella catarrhalis [MC]), differential cell counts (total cell count [TCC], neutrophil %, eosinophil %) and a panel of inflammatory mediators. Associations between bacterial load and both inflammatory mediators and differential cell counts were explored. Correlations were considered significant if p<0.01. Results: Positive correlations were found between CFU and TNFα (rs=0.42,p=0.001), IL1β (rs=0.39,p=0.001) and IL10 (rs=0.57,p<0.001). Several positive correlations were found between qPCR HI and inflammatory mediators (table 1) . qPCR MC and qPCR SP did not positively correlate with CFU, sputum cell counts or any sputum inflammatory mediator. View this table: Table 1: Correlations between H. influenzae qPCR load and inflammatory mediators Conclusions: Stable state H. influenzae qPCR load is associated with an increased sputum total cell count, neutrophil percent and inflammatory mediators in COPD. The same associations were not seen with qPCR S. pneumoniae and M. catarrhalis .

Introduction Interpretation of single point IGRA testing with QuantiFERON-TB Gold In Tube (QFT) to identify recently acquired latent M.tuberculosis infection (LTBI) in contacts of active TB may be confounded by previous exposure (false positive) or testing too soon after exposure, prior to development of adaptive immunity (false negative). Aim To determine the relationship between exposure duration & quantitative QFT in household contacts of smear positive pulmonary TB with heterogeneous risk of remote LTBI. We hypothesise a closer association of QFT with exposure time in contacts at low risk of remote LTBI. To estimate the exposure duration needed prior to testing for QFT to reliably identify LTBI. Method 136 QFT tested contacts of 14 smear positive pulmonary TB cases were studied. Quantitative QFT & index symptom duration (days) were recorded. Risk of remote LTBI was scored by age & country of birth and contacts were categorised into low, moderate and high risk subgroups. Result There was a weak correlation between QFT value in contacts and their exposure duration (R 2 = 0.06; p=0.01). Subgroup analysis identified this correlation to be significant in contacts at low risk of remote LTBI [UK born, 2 =0.31; p 120 days after onset of index symptoms. In contrast, 3 of 33 at moderate risk and 15 of 32 at high risk of remote LTBI were QFT positive with earlier ( Conclusion Adaptive immunity to recently acquired LTBI is detectable with QFT testing if delayed 120 days after onset of index symptoms in close contacts at low risk of previous LTBI.

BACKGROUND:The efffectiveness of tuberculosis (TB) contact screening programmes using interferon γ release assays remains uncertain as prospective contact TB risk is not well characterised. OBJECTIVES:To quantify 2-year TB risk and evaluate screening performance with single-step QuantiFERON TB Gold-In Tube (QFT) in adult contacts. To compare TB risk between QFT tested subgroups stratified by exposure type (smear positive pulmonary (SP) versus non-smear positive (NSP) TB) and age (younger (16-35 years) versus older (≥36 years)). METHODS:Screening involved QFT testing in older contacts of SP and all younger contacts, 8-12 weeks after index notification. Chemoprevention (3RH) was offered to QFT positive (+) younger adults. TB risk was determined in a prospective cohort study. RESULTS:43 TB events occurred in 1769 adult contacts observed for median 717 days (2-year rate (95% CI)=2·5% (1.7 to 3.2)). Index-contact strain matching was demonstrable for 18 of 22 (82%) paired samples. No contacts (0/98) receiving 3RH developed TB. 215 of 817 appropriately tested adults (26.3%) were QFT+. 14 of 112 untreated QFT+ adults developed TB (2-year rate (95% CI)=13·4% (7.7 to 21.1)). The model required 35 contacts screened with QFT to identify one contact developing TB at 2 years. TB rates were comparable in QFT+ contacts of SP and NSP (rate ratio (RR)=0.98, p=0·962). For QFT+ older contacts, the disease rate was lower (8.9% (3.3 to 19.1)) and similar to the overall group rate (RR=1.4, p=0.503). CONCLUSIONS:QFT based single-step contact screening is effective in young adults.

Rationale: Exacerbations of chronic obstructive pulmonary disease (COPD) are heterogeneous with respect to inflammation and etiology.Objectives: Investigate biomarker expression in COPD exacerbations to identify biologic clusters and determine biomarkers that recognize clinical COPD exacerbation phenotypes, namely those associated with bacteria, viruses, or eosinophilic airway inflammation.Methods: Patients with COPD were observed for 1 year at stable and exacerbation visits. Biomarkers were measured in sputum and serum. Viruses and selected bacteria were assessed in sputum by polymerase chain reaction and routine diagnostic bacterial culture. Biologic phenotypes were explored using unbiased cluster analysis and biomarkers that differentiated clinical exacerbation phenotypes were investigated.Measurements and Main Results: A total of 145 patients (101 men and 44 women) entered the study. A total of 182 exacerbations were captured from 86 patients. Four distinct biologic exacerbation clusters were identified. These were bacterial-, viral-, or eosinophilic-predominant, and a fourth associated with limited changes in the inflammatory profile termed “pauciinflammatory.” Of all exacerbations, 55%, 29%, and 28% were associated with bacteria, virus, or a sputum eosinophilia. The biomarkers that best identified these clinical phenotypes were sputum IL-1β, 0.89 (area under receiver operating characteristic curve) (95% confidence interval [CI], 0.83–0.95); serum CXCL10, 0.83 (95% CI, 0.70–0.96); and percentage peripheral eosinophils, 0.85 (95% CI, 0.78–0.93), respectively.Conclusions: The heterogeneity of the biologic response of COPD exacerbations can be defined. Sputum IL-1β, serum CXCL10, and peripheral eosinophils are biomarkers of bacteria-, virus-, or eosinophil-associated exacerbations of COPD. Whether phenotype-specific biomarkers can be applied to direct therapy warrants further investigation.