Biomarkers in the management of COPD

MCP-4 and Eotaxin-3 Are Novel Biomarkers for Chronic Obstructive Pulmonary Disease

The aim of our study was to examine the production of monocyte chemoattractant protein (MCP-4) and eotaxin-3 during the onset and progression of COPD. The expression levels of MCP-4 and eotaxin-3 were evaluated in COPD samples and healthy controls using immunostaining and ELISA. The relationship between the clinic pathological features in the participants and the expression of MCP-4 and eotaxin-3 were evaluated. The association of MCP-4/eotaxin-3 production in COPD patients was also determined. The results revealed enhanced production of MCP-4 and eotaxin-3 in COPD patients especially the cases with AECOPD in both bronchial biopsies and bronchial washing fluid samples. Furthermore, the expression signatures of MCP-4/eotaxin-3 show high AUC values in distinguishing COPD patients and healthy volunteers and AECOPD and stable COPD cases, respectively. Additionally, the number of MCP-4/eotaxin-3 positive cases was notably increased in AECOPD patients compared to those with stable COPD. Moreover, the expression of MCP-4 and eotaxin-3 was positively correlated in COPD and AECOPD cases. In addition, the levels of MCP-4 and eotaxin-3 could be increased in HBEs stimulated with LPS, which is a risk factor of COPD. Moreover, MCP-4 and eotaxin-3 may exert their regulatory functions in COPD by regulating CCR2, 3, and 5. These data indicated that MCP-4 and eotaxin-3 were potential markers for the clinical course of COPD, which could provide guidance for accurate diagnosis and treatment for this disease in future clinical practice.

EVs-miRNA: The New Molecular Markers for Chronic Respiratory Diseases

Idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), asthma and sleep disorders are chronic respiratory diseases that affect the airways, compromising lung function over time. These diseases affect hundreds of millions of people around the world and their frequency seems to be increasing every year. Extracellular vesicles (EVs) are small-sized vesicles released by every cell in the body. They are present in most body fluids and contain various biomolecules including proteins, lipids, mRNA and non-coding RNA (micro-RNA). The EVs can release their cargo, specifically micro-RNAs (miRNAs), to both neighboring and/or distal cells, playing a fundamental role in cell-cell communication. Recent studies have shown their possible role in the pathogenesis of various chronic respiratory diseases. The expression of miRNAs and, in particular, of miRNAs contained within the extracellular vesicles seems to be a good starting point in order to identify new potential biomarkers of disease, allowing a non-invasive clinical diagnosis. In this review we summarize some studies, present in the literature, about the functions of extracellular vesicles and miRNAs contained in extracellular vesicles in chronic respiratory diseases and we discuss the potential clinical applications of EVs and EVs-miRNAs for their possible use such as future biomarkers.

The importance of neopterin in COVID-19: The prognostic value and relation with the disease severity

Coronavirus Disease 2019 [COVID-19], caused by severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2], has rapidly evolved into a global health emergency. Neopterin [NPT], produced by macrophages when stimulated with interferon [IFN-]gamma, is an essential cytokine in the antiviral immune response. NPT has been used as a marker for the early assessment of disease severity in different diseases. The leading cause of NPT production is the pro-inflammatory cytokine IFN-. Macrophage activation has also been revealed to be linked with disease severity in SARS-CoV-2 patients. We demonstrate the importance of NPT in the pathogenesis of SARS-CoV-2 and suggest that targeting NPT in SARS-CoV-2 infection may be critical in the early prediction of disease progression and provision of timely management of infected individuals.

2021 Guideline for the Management of COPD Exacerbations: Emergency Medicine Association of Turkey (EMAT) / Turkish Thoracic Society (TTS) Clinical Practice Guideline Task Force

Chronic obstructive pulmonary disease (COPD) is an important public health problem that manifests with exacerbations and causes serious mortality and morbidity in both developed and developing countries. COPD exacerbations usually present to emergency departments, where these patients are diagnosed and treated. Therefore, the Emergency Medicine Association of Turkey and the Turkish Thoracic Society jointly wanted to implement a guideline that evaluates the management of COPD exacerbations according to the current literature and provides evidence-based recommendations. In the management of COPD exacerbations, we aim to support the decision-making process of clinicians dealing with these patients in the emergency setting.

A perspective for chronic obstructive pulmonary disease (COPD) management: six key clinical questions to improve disease treatment

INTRODUCTION

In 2011, the GOLD recommendations for the treatment of Chronic Obstructive Pulmonary Disease (COPD) introduced new clinical elements to classify the severity of the disease and to guide pharmacological choice. For the first time in the GOLD documents, treatment decision was no longer guided only by pulmonary function, but by a more complex combination of pulmonary function and clinical aspects. The recent versions of the GOLD recommendations introduce new aspects for the clinicians and pose new question for the management of the disease. In addition, inflammatory biomarkers and blood eosinophil levels, have been considered to guide treatment selection.

AREA COVERED

The evolution of disease management proposed by the GOLD document opens several areas of debate. A series of roundtable discussions among respiratory physicians took place in Italy to address key clinical questions. Particularly, the role of lung function and the use of biomarkers, the adherence to international guidelines and the possibility to personalize the pharmacological approach in COPD patients have been discussed, summarized and analyzed.

EXPERT OPINION

The authors believe that the development of a precision medicine approach tailoring the specific treatment for each patient is the goal of COPD management and may be achieved by considering the phenotypic classification of COPD patients.

Chronic Obstructive Pulmonary Disease in the Intensive Care Unit: Antibiotic Treatment of Severe Chronic Obstructive Pulmonary Disease Exacerbations

Patients who suffer from chronic obstructive pulmonary disease (COPD) often experience deterioration of baseline respiratory symptoms, acute exacerbations of COPD (AECOPD), that become more frequent with disease progression. Based on symptom severity, approximately 20% of these patients will require hospitalization. The most common indicators for intensive care unit (ICU) admission have been found to be worsening or impending respiratory failure and hemodynamic instability. Bacterial and viral bronchial infections are the causative triggers in the majority of COPD exacerbations in the ICU, with a comprehensive assessment revealing them in 72% of cases. The distribution of bacterial pathogens involved in AECOPD requiring ICU admission show an increased incidence of gram-negative respiratory isolates, including Pseudomonas and Enterobacteriaceae spp., when compared with outpatient exacerbations. Evaluation of these patients requires careful attention to comorbid conditions. An effort to rapidly obtain lower respiratory samples for microbiological samples prior to initiation of antibiotics should be made as adequate samples can guide subsequent modifications of antibiotic treatment if the clinical response to empiric treatment is poor. Empiric antibiotic treatment should be promptly initiated in all patients with a major consideration for the choice being the presence of risk factors for Pseudomonas infection. Evaluation of clinical response at 48 to 72 hours is crucial, and total duration of antibiotics of 5 to 7 days should be adequate.

Acute exacerbations of chronic obstructive pulmonary disease: in search of diagnostic biomarkers and treatable traits

Acute exacerbations of chronic obstructive pulmonary disease (COPD) are associated with a significant mortality, health and economic burden. Their diagnosis, assessment and management remain suboptimal and unchanged for decades. Recent clinical and translational studies revealed that the significant heterogeneity in mechanisms and outcomes of exacerbations could be resolved by grouping them etiologically. This is anticipated to lead to a better understanding of the biological processes that underlie each type of exacerbation and to allow the introduction of precision medicine interventions that could improve outcomes. This review summarises novel data on the diagnosis, phenotyping, targeted treatment and prevention of COPD exacerbations.

Association of platelet count with all-cause mortality and risk of cardiovascular and respiratory morbidity in stable COPD

Background

Platelet count is a prognostic indicator in the general population and elderly. Thrombocytosis during acute exacerbation of COPD (AECOPD) has been associated with mortality; however, the relationship between platelet count and mortality in stable COPD is unknown.

Methods

We performed post hoc secondary analysis on a subsample of 1797 patients in the Study to Understand Mortality and Morbidity in COPD (SUMMIT) who had blood samples drawn at baseline. Participants were current or former smokers, 40–80 years old with moderate COPD and history or increased risk of cardiovascular (CV) disease. The primary outcome was on and post-treatment all-cause mortality. Secondary outcomes included first-on-treatment moderate/severe AECOPD and on-treatment CV composite event (CV death, myocardial infarction, stroke, unstable angina and transient ischemic attack). Multivariable Cox proportional hazards models were used to investigate study endpoint associations with platelet count quintile grouping, continuous platelet count utilizing two-term fractional polynomials, and categories of low, normal and high platelet count (< 150, ≥150 to < 300, ≥300 × 10⁹/L).

Results

Patients were followed for 2.3 ± 0.9 years for vital status and 1.6 ± 1.1 years for morbidity endpoints during which 105 (5.8%) died, 651 (36.2%) experienced AECOPD (159 with severe AECOPD) and 86 (4.8%) experienced a CV event. A U-shaped association between platelet count and all-cause mortality was observed. Compared to the third quintile group (Q3) of platelet count, risk of death was increased in the lowest quintile group (Q1; hazard ratio [HR]: 1.73; 95% confidence interval [CI]: 0.93–3.23) and highest quintile group (Q5; HR: 1.66; 95%CI: 0.89–3.10), though point estimates were imprecise. Using clinical cutoffs, compared with normal platelet counts (≥150 to < 300 × 10⁹/L), risk of all-cause mortality was nominally increased among patients with thrombocytopenia (HR: 1.46; 95%CI: 0.81–2.64) and high platelet count (HR: 1.66; 95%CI: 0.96–2.86). Compared with Q3, CV events were nominally increased for Q5 (HR: 1.71; 95%CI: 0.83–3.49) and Q1 (HR: 1.41; 95%CI: 0.70, 2.85). There was no association between platelet count and AECOPD.

Conclusions

In stable COPD platelet count demonstrated a U-shaped association with increased risk of 3-year all-cause mortality, though a platelet count level above or below which risk of mortality was increased could not be definitively identified.

Trial registration

ClinicalTrials.gov NCT01313676.

Bacteria in the respiratory tract-how to treat? Or do not treat?

BACKGROUND

Acute and chronic respiratory tract infections are a common cause of inappropriate antimicrobial prescription. Antimicrobial therapy leads to the development of resistance and the emergence of opportunistic pathogens that substitute the indigenous microbiota.

METHODS

This review explores the major challenges and lines of research to adequately establish the clinical role of bacteria and the indications for antimicrobial treatment, and reviews novel therapeutic approaches.

RESULTS

In patients with chronic pulmonary diseases and structural disturbances of the bronchial tree or the lung parenchyma, clinical and radiographic signs and symptoms are almost constantly present, including a basal inflammatory response. Bacterial adaptative changes and differential phenotypes are described, depending on the clinical role and niche occupied. The respiratory tract has areas that are potentially inaccessible to antimicrobials. Novel therapeutic approaches include new ways of administering antimicrobials that may allow intracellular delivery or delivery across biofilms, targeting the functions essential for infection, such as regulatory systems, or the virulence factors required to cause host damage and disease. Alternatives to antibiotics and antimicrobial adjuvants are under development.

CONCLUSIONS

Prudent treatment, novel targets, and improved drug delivery systems will contribute to reduce the emergence of antimicrobial resistance in lower respiratory tract infections.

A Systematic Review of Diagnostic Biomarkers of COPD Exacerbation

The aims of this systematic review were to determine which blood-based molecules have been evaluated as possible biomarkers to diagnose chronic obstructive pulmonary disease (COPD) exacerbations (AECOPD) and to ascertain the quality of these biomarker publications. Patients of interest were those that have been diagnosed with COPD. MEDLINE, EMBASE, and CINAHL databases were searched systematically through February 2015 for publications relating to AECOPD diagnostic biomarkers. We used a modified guideline for the REporting of tumor MARKer Studies (mREMARK) to assess study quality. Additional components of quality included the reporting of findings in a replication cohort and the use of receiver-operating characteristics area-under-the curve statistics in evaluating performance. 59 studies were included, in which the most studied biomarkers were C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α). CRP showed consistent elevations in AECOPD compared to control subjects, while IL-6 and TNF-α had variable statistical significance and results. mREMARK scores ranged from 6 to 18 (median score of 13). 12 articles reported ROC analyses and only one study employed a replication cohort to confirm biomarker performance. Studies of AECOPD diagnostic biomarkers remain inconsistent in their reporting, with few studies employing ROC analyses and even fewer demonstrating replication in independent cohorts.

Mental health, serum biomarkers and survival in severe COPD: a pilot study

Background

Chronic obstructive pulmonary disease (COPD) impairs physical status and impacts on mental health. This prospective study was designed to assess associations between mental health and systemic biomarkers, and their combined relationship with long-term survival in stable severe COPD.

Methods

Forty-five patients with severe but stable COPD (forced expiratory volume in 1 s of 29.8 (quartiles: 22.6; 41.4) %predicted) were assessed using the Hospital Anxiety and Depression Scale (HADS), the Patient Health Questionnaire (PHQ), St. George’s Respiratory Questionnaire and the State-Trait Anxiety Inventory (STAI). The following serum biomarkers were measured: 25-OH-cholecalciferol, C-reactive protein, erythrocyte sedimentation rate, leucocyte number, serum amyloid-A (SA-A), N-terminal pro-brain natriuretic peptide, troponin I, glycosylated haemoglobin, haemoglobin (Hb), haematocrit (Hc), creatinine and thyroid-stimulating hormone. Patients were followed-up for 36 months. Associations between aspects of mental health and biomarkers, and their utility as predictors of 3-year survival were evaluated by regression analyses.

Results

The prevalence of anxiety (HADS-A: 89.9 %), depression (HADS-D: 58.8 %; PHQ: 60.6 %), somatisation (PHQ-15: 81.8 %) and psychosocial stress (PHQ-stress: 60.6 %) was high. There was a significant positive association between the leucocyte count and SA-A level with STAI-trait anxiety (p = 0.03 and p = 0.005, respectively), and between leucocytes and PHQ-stress (p = 0.043). Hb and Hc were significantly negatively associated with HADS-depression (p = 0.041 and p = 0.031, respectively). Univariate Cox regression analyses revealed that leucocyte count (hazard ratio (HR) 2.976, 95 % CI 1.059-8.358; p = 0.038), and stress (HR 4.922, 95 % CI 1.06–22.848; p = 0.042) were linked to long-term survival. In multivariate Cox regression analyses, including known risk factors for survival in COPD, PHQ-stress (HR 45.63, 95 % CI 1.72–1,208.48; p = 0.022) remained significantly associated with survival.

Conclusion

In this pilot study different dimensions of mental health were correlated to serum biomarkers, probably reflecting systemic effects of COPD. While leucocyte number and PHQ-stress were associated with long-term survival in univariate analyses, PHQ-stress remained in multivariate analyses as independent prognostic factor.

Real-world characterization and differentiation of the Global Initiative for Chronic Obstructive Lung Disease strategy classification

BACKGROUND

This study aimed to characterize and differentiate the Global Initiative for Chronic Obstructive Lung Disease (GOLD) strategy 2011 cut points through the modified Medical Research Council dyspnea scale (mMRC) and chronic obstructive pulmonary disease (COPD) assessment test (CAT).

METHODS

Analysis of COPD patient data from the 2012 Adelphi Respiratory Disease Specific Program was conducted in Europe and US. Matched data from physicians and patients included CAT and mMRC scores. Receiver operating characteristic curves and kappa analysis determined a cut point for CAT and mMRC alignment and thus defined patient movement ("movers") within GOLD groups A-D, depending on the tool used. Logistic regression analysis, with a number of physician- and patient-reported covariates, characterized those movers.

RESULTS

Comparing GOLD-defined high-symptom patients using mMRC and CAT cut points (≥2 and ≥10, respectively), there were 890 (53.65%) movers; 887 of them (99.66%) moved from less symptomatic GOLD groups A and C (using mMRC) to more symptomatic groups B and D (using CAT). For receiver operating characteristic (area under the curve: 0.82, P<0.001) and kappa (maximized: 0.45) recommended CAT cut points of ≥24 and ≥26, movers reduced to 429 and 403 patients, respectively. Logistic regression analysis showed variables significantly associated with movers were related to impact on normal life, age, cough, and sleep (all P<0.05). Within movers, direction of movement was significantly associated with the same variables (all P<0.05).

CONCLUSION

Use of current mMRC or CAT cut points leads to inconsistencies for COPD assessment classification. It is recommended that cut points are aligned and both tools administered simultaneously for optimal patient care and to allow for closer management of movers. Our research may suggest an opportunity to investigate a combined score approach to patient management based on the worst result of mMRC and CAT. The reduced number of remaining movers may then identify patients who have greater impact of disease and may require a more personalized treatment plan.

C-reactive protein measurements as a marker of the severity of chronic obstructive pulmonary disease exacerbations

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disease of the lungs. Acute exacerbations of COPD (AE-COPD) are a result of infectious or non-infectious instances. In our study, we aimed to determine whether serum C-reactive protein (CRP) levels are predictive indicators for disease severity and prognosis in hospitalized patients with AE-COPD. A total of 64 patients (36 regular ward and 28 ICU patients) were included in the study. Cases were identified and classified according to the Global Initiative for COPD. The first CRP test levels at acceptance at the ward or intensive care unit were counted in the study. CRP levels of patients in intensive care were significantly higher than those of patients in the regular ward. Mean values of CRP were detected to be 6.28 ± 6.53 mg/dl in the regular ward cases and 16.9 ± 12.03 mg/dl in the ICU patients (p < 0.01). The stage of COPD did not indicate a significant difference in terms of CRP values. Mean CRP values were found to be 16.02 ± 6.95 mg/dl in mortal cases and 9.76 ± 11.09 mg/dl in survivors (p < 0.01). High CRP levels were considered as a prognostic parameter and indicator of severity of AE-COPD. Increased mortality risk was found to be associated with high CRP values.

Correlation of inflammatory and cardiovascular biomarkers with pneumonia severity scores

PURPOSE

To assess the correlation of procalcitonin (PCT), C-reactive protein (CRP), neopterin, mid-regional pro-atrial natriuretic peptide (MR-proANP), and mid-regional pro-adrenomedullin (MR-proADM) with severity risk scores: severe CAP (SCAP) and SMART-COP in patients with community-acquired pneumonia (CAP), as well as short term prognosis and to determine the correlation with mortality risk scores.

METHODS

Eighty-five patients with a final diagnosis of pneumonia were consecutively included during a two month period. Epidemiological, clinical, microbiological, and radiological data were recorded. Patients were stratified according to the PSI, CURB-65, SCAP and SMART-COP. Complications were defined as respiratory failure/shock, need of ICU, and death. Plasma samples were collected at admission.

RESULTS

MR-proANP and MR-proADM showed significantly higher levels in high risk SCAP group in comparison to low risk. When considering SMART-COP none of the biomarkers showed statistical differences. MR-proADM levels were high in patients with high risk of needing intensive respiratory or vasopressor support according to SMRT-CO. Neopterin and MR-proADM were significantly higher in patients that developed complications. PCT and MR-proADM showed significantly higher levels in cases of a definite bacterial diagnosis in comparison to probable bacterial, and unknown origin. MR-proANP and MR-proADM levels increased statistically according to PSI and CURB-65.

CONCLUSIONS

Biomarker levels are higher in pneumonia patients with a poorer prognosis according to SCAP and SMART-COP indexes, and to the development of complications.

An omics strategy for discovering pulmonary biomarkers potentially relevant to the evaluation of tobacco products

Smoking is known to cause serious lung diseases including chronic bronchitis, chronic obstructive lung disease, obstruction of small airways, emphysema and cancer. Tobacco smoke is a complex chemical aerosol containing at least 8000 chemical constituents, either tobacco derived or added by tobacco product manufacturers. Identification of all of the toxic agents in tobacco smoke is challenging, and efforts to understand the mechanisms by which tobacco use causes disease will be informed by new biomarkers of exposure and harm. In 2009, President Obama signed into law the Family Smoking Prevention and Tobacco Control Act granting the US FDA the authority to regulate tobacco products to protect public health. This perspective article presents the background, rationale and strategy for using omics technologies to develop new biomarkers, which may be of interest to the FDA when implementing the Family Smoking Prevention and Tobacco Control Act.

Usefulness of consecutive biomarkers measurement in the management of community-acquired pneumonia

The aim of this study was to investigate whether procalcitonin (PCT), neopterin, C-reactive protein (CRP), and mid regional pro-atrial natriuretic peptide (MR-proANP) levels at admission and during the clinical course can be useful for the management of patients with pneumonia. The study population consisted of 75 patients with clinical and radiological diagnosis of pneumonia. Serum samples were collected at admission and during hospitalization. Complications were defined as intensive care unit (ICU) admission or death. The levels of PCT were significantly higher in pneumonia of definite bacterial origin in comparison to probable bacterial or unknown origin. The PCT levels were higher in pneumococcal pneumonia. The PCT and MR-proANP levels increased significantly according to the Pneumonia Severity Index (PSI). All biomarkers levels are higher in patients developing complications and who were dying. The serial levels of MR-proANP remain significantly elevated in patients developing complications and in patients classified in PSI and CURB-65 risk groups. In patients not developing complications, there is a significant decrease in the PCT levels. PCT can be useful for identifying pneumonia etiology. PCT and MR-proANP levels correlate with pneumonia severity rules. PCT and MR-proANP serial measurements can be useful for predicting short-term prognosis. Systemic biomarkers can provide additional information regarding clinical evolution, because these are dynamic and can be measured daily.

Value of procalcitonin, C-reactive protein, and neopterin in exacerbations of chronic obstructive pulmonary disease

Objective:

The identification of biological markers in order to assess different aspects of COPD is an area of growing interest. The objective of this study was to investigate whether levels of procalcitonin (PCT), C-reactive protein (CRP), and neopterin in COPD patients could be useful in identifying the etiological origin of the exacerbation and assessing its prognosis.

Methods:

We included 318 consecutive COPD patients: 46 in a stable phase, 217 undergoing an exacerbation, and 55 with pneumonia. A serum sample was collected from each patient at the time of being included in the study. A second sample was also collected 1 month later from 23 patients in the exacerbation group. We compared the characteristics, biomarker levels, microbiological findings, and prognosis in each patient group. PCT and CRP were measured using an immunofluorescence assay. Neopterin levels were measured using a competitive immunoassay.

Results:

PCT and CRP showed significant differences among the three patient groups, being higher in patients with pneumonia, followed by patients with exacerbation (P < 0.0001). For the 23 patients with paired samples, PCT and CRP levels decreased 1 month after the exacerbation episode, while neopterin increased. Neopterin showed significantly lower levels in exacerbations with isolation of pathogenic bacteria, but no differences were found for PCT and CRP. No significant differences were found when comparing biomarker levels according to the Gram result: PCT (P = 0.191), CRP (P = 0.080), and neopterin (P = 0.109). However, median values of PCT and CRP were high for Streptococcus pneumoniae, Staphylococcus aureus, and enterobacteria. All biomarkers were higher in patients who died within 1 month after the sample collection than in patients who died later on.

Conclusions:

According to our results, biomarker levels vary depending on the clinical status. However, the identification of the etiology of infectious exacerbation by means of circulating biomarkers is encouraging, but its main disadvantage is the absence of a microbiological gold standard, to definitively demonstrate their value. High biomarker levels during an exacerbation episode correlate with the short-term prognosis, and therefore their measurement can be useful for COPD management.

Usefulness of mid regional pro-atrial natriuretic peptide in the exacerbations of chronic obstructive pulmonary disease

BACKGROUND

A recent approach for the management of chronic obstructive pulmonary disease (COPD) is the measurement of systemic biomarkers. The aim of this study was to evaluate the usefulness of mid regional pro-atrial natriuretic peptide (MR-proANP) to predict short and long term prognosis.

METHODS

We included 318 COPD patients: 46 in a stable phase, 217 undergoing an exacerbation and 55 with pneumonia. Serum samples were collected at admission. For 20 exacerbated patients, we also collected a second sample one month later. MR-proANP was measured by an inmunofluorescent assay.

RESULTS

Statistically higher levels of MR-proANP were found in patients with pneumonia when comparing to patients in the stable state (p=0.031). For those patients with paired samples, MR-proANP decreased statistically one month later (p=0.027). MR-proANP showed significant lower levels in exacerbations with isolation of pathogenic bacteria (p=0.011). MR-proANP levels were higher in patients that died within one month, decreasing as long as the moment of death occurred later on (p=0.163).

CONCLUSIONS

The identification of exacerbation etiology by means of MR-proANP is not clinically reliable. Levels of MR-proANP vary depending on the clinical status, being higher during pneumonia in comparison to the stable state. MR-proANP levels were higher in patients that died within one month after the exacerbation episode.