Lower respiratory tract infection in the community: associations between viral aetiology and illness course.

OBJECTIVES: This study determined associations between respiratory viruses and subsequent illness course in primary care adult patients presenting with acute cough and/or suspected lower respiratory tract infection. METHODS: A prospective European primary care study recruited adults with symptoms of lower respiratory tract infection between November 2007 and April 2010. Real-time in-house polymerase chain reaction (PCR) was performed to test for six common respiratory viruses. In this secondary analysis, symptom severity (scored 1 = no problem, 2 = mild, 3 = moderate, 4 = severe) and symptom duration were compared between groups with different viral aetiologies using regression and Cox proportional hazard models, respectively. Additionally, associations between baseline viral load (cycle threshold (Ct) value) and illness course were assessed. RESULTS: The PCR tested positive for a common respiratory virus in 1354 of the 2957 (45.8%) included patients. The overall mean symptom score at presentation was 2.09 (95% confidence interval (CI) 2.07-2.11) and the median duration until resolution of moderately bad or severe symptoms was 8.70 days (interquartile range 4.50-11.00). Patients with influenza virus, human metapneumovirus (hMPV), respiratory syncytial virus (RSV), coronavirus (CoV) or rhinovirus had a significantly higher symptom score than patients with no virus isolated (0.07-0.25 points or 2.3-8.3% higher symptom score). Time to symptom resolution was longer in RSV infections (adjusted hazard ratio (AHR) 0.80, 95% CI 0.65-0.96) and hMPV infections (AHR 0.77, 95% CI 0.62-0.94) than in infections with no virus isolated. Overall, baseline viral load was associated with symptom severity (difference 0.11, 95% CI 0.06-0.16 per 10 cycles decrease in Ct value), but not with symptom duration. CONCLUSIONS: In healthy, working adults from the general community presenting at the general practitioner with acute cough and/or suspected lower respiratory tract infection other than influenza impose an illness burden comparable to influenza. Hence, the public health focus for viral respiratory tract infections should be broadened.

Recommendations for antibacterial therapy in adults with COVID-19 e an evidence based guideline

The Dutch Working Party on Antibiotic Policy constituted a multidisciplinary expert committee to provide evidence-based recommendation for the use of antibacterial therapy in hospitalized adults with a respiratory infection and suspected or proven 2019 Coronavirus disease (COVID-19). We performed a literature search to answer four key questions. The committee graded the evidence and developed recommendations by using Grading of Recommendations Assessment, Development, and Evaluation methodology. We assessed evidence on the risk of bacterial infections in hospitalized COVID-19 patients, the associated bacterial pathogens, how to diagnose bacterial infections and how to treat bacterial infections. Bacterial co-infection upon admission was reported in 3.5% of COVID-19 patients, while bacterial secondary infections during hospitalization occurred up to 15%. No or very low quality evidence was found to answer the other key clinical questions. Although the evidence base on bacterial infections in COVID-19 is currently limited, available evidence supports restrictive antibiotic use from an antibiotic stewardship perspective, especially upon admission. To support restrictive antibiotic use, maximum efforts should be undertaken to obtain sputum and blood culture samples as well as pneumococcal urinary antigen testing. We suggest to stop antibiotics in patients who started antibiotic treatment upon admission when representative cultures as well as urinary antigen tests show no signs of involvement of bacterial pathogens after 48 hours. For patients with secondary bacterial respiratory infection we recommend to follow other guideline recommendations on antibacterial treatment for patients with hospital-acquired and ventilator-associated pneumonia. An antibiotic treatment duration of five days in patients with COVID-19 and suspected bacterial respiratory infection is recommended upon improvement of signs, symptoms and inflammatory markers. Larger, prospective studies about the epidemiology of bacterial infections in COVID-19 are urgently needed to confirm our conclusions and ultimately prevent unnecessary antibiotic use during the COVID-19 pandemic.

Prediction model for pneumonia in primary care patients with an acute respiratory tract infection: role of symptoms, signs, and biomarkers.

BACKGROUND: Diagnosing pneumonia can be challenging in general practice but is essential to distinguish from other respiratory tract infections because of treatment choice and outcome prediction. We determined predictive signs, symptoms and biomarkers for the presence of pneumonia in patients with acute respiratory tract infection in primary care. METHODS: From March 2012 until May 2016 we did a prospective observational cohort study in three radiology departments in the Leiden-The Hague area, The Netherlands. From adult patients we collected clinical characteristics and biomarkers, chest X ray results and outcome. To assess the predictive value of C-reactive protein (CRP), procalcitonin and midregional pro-adrenomedullin for pneumonia, univariate and multivariate binary logistic regression were used to determine risk factors and to develop a prediction model. RESULTS: Two hundred forty-nine patients were included of whom 30 (12%) displayed a consolidation on chest X ray. Absence of runny nose and whether or not a patient felt ill were independent predictors for pneumonia. CRP predicts pneumonia better than the other biomarkers but adding CRP to the clinical model did not improve classification (- 4%); however, CRP helped guidance of the decision which patients should be given antibiotics. CONCLUSIONS: Adding CRP measurements to a clinical model in selected patients with an acute respiratory infection does not improve prediction of pneumonia, but does help in giving guidance on which patients to treat with antibiotics. Our findings put the use of biomarkers and chest X ray in diagnosing pneumonia and for treatment decisions into some perspective for general practitioners.

Implementation and evaluation of an antimicrobial stewardship programme in companion animal clinics: A stepped-wedge design intervention study.

BACKGROUND: To curb increasing resistance rates, responsible antimicrobial use (AMU) is needed, both in human and veterinary medicine. In human healthcare, antimicrobial stewardship programmes (ASPs) have been implemented worldwide to improve appropriate AMU. No ASPs have been developed for and implemented in companion animal clinics yet. OBJECTIVES: The objective of the present study was to implement and evaluate the effectiveness of an ASP in 44 Dutch companion animal clinics. The objectives of the ASP were to increase awareness on AMU, to decrease total AMU whenever possible and to shift AMU towards 1st choice antimicrobials, according to Dutch guidelines on veterinary AMU. METHODS: The study was designed as a prospective, stepped-wedge, intervention study, which was performed from March 2016 until March 2018. The multifaceted intervention was developed using previous qualitative and quantitative research on current prescribing behaviour in Dutch companion animal clinics. The number of Defined Daily Doses for Animal (DDDAs) per clinic (total, 1st, 2nd and 3rd choice AMU) was used to quantify systemic AMU. Monthly AMU data were described using a mixed effect time series model with auto-regression. The effect of the ASP was modelled using a step function and a change in the (linear) time trend. RESULTS: A statistically significant decrease of 15% (7%-22%) in total AMU, 15% (5%-24%) in 1st choice AMU and 26% (17%-34%) in 2nd choice AMU was attributed to participation in the ASP, on top of the already ongoing time trends. Use of 3rd choice AMs did not significantly decrease by participation in the ASP. The change in total AMU became more prominent over time, with a 16% (4%-26%) decrease in (linear) time trend per year. CONCLUSIONS: This study shows that, although AMU in Dutch companion animal clinics was already decreasing and changing, AMU could be further optimised by participation in an antimicrobial stewardship programme.

Burden of disease in children with respiratory tract infections in primary care: diary-based cohort study.

BACKGROUND: Respiratory tract infections (RTIs) are a common reason for children to consult in general practice. Antibiotics are often prescribed, in part due to miscommunication between parents and GPs. The duration of specific respiratory symptoms has been widely studied. Less is known about illness-related symptoms and the impact of these symptoms on family life, including parental production loss. Better understanding of the natural course of illness-related symptoms in RTI in children and impact on family life may improve GP-parent communication during RTI consultations. OBJECTIVE: To describe the general impact of RTI on children and parents regarding illness-related symptoms, absenteeism from childcare, school and work, use of health care facilities, and the use of over-the-counter (OTC) medication. METHODS: Prospectively collected diary data from two randomized clinical trials in children with RTI in primary care (n = 149). Duration of symptoms was analysed using survival analysis. RESULTS: Disturbed sleep, decreased intake of food and/or fluid, feeling ill and/or disturbance at play or other daily activities are very common during RTI episodes, with disturbed sleep lasting longest. Fifty-two percent of the children were absent for one or more days from childcare or school, and 28% of mothers and 20% of fathers reported absence from work the first week after GP consultation. Re-consultation occurred in 48% of the children. OTC medication was given frequently, particularly paracetamol and nasal sprays. CONCLUSION: Appreciation of, and communication about the general burden of disease on children and their parents, may improve understanding between GPs and parents consulting with their child.

Aetiology of lower respiratory tract infection in adults in primary care: a prospective study in 11 European countries.

OBJECTIVES: To describe the role of bacteria (including bacterial resistance), viruses (including those recently described) and mixed bacterial-viral infections in adults presenting to primary care with lower respiratory tract infection (LRTI). METHODS: In all, 3104 adults with LRTI were enrolled, of whom 141 (4.5%) had community-acquired pneumonia (CAP), and 2985 matched controls in a prospective study in 16 primary care networks in Europe, and followed patients up at 28-35 days. We detected Streptococcus pneumoniae and Haemophilus influenzae and assessed susceptibility, atypical bacteria and viruses. RESULTS: A potential pathogen was detected in 1844 (59%) (in 350 (11%) bacterial pathogens only, in 1190 (38%) viral pathogens only, and in 304 (10%) both bacterial and viral pathogens). The most common bacterial pathogens isolated were S. pneumoniae (5.5% overall, 9.2% in CAP patients) and H. influenzae (5.4% overall, 14.2% in CAP patients). Less than 1% of S. pneumoniae were highly resistant to penicillin and 12.6% of H. influenzae were ß-lactamase positive. The most common viral pathogens detected were human rhinovirus (20.1%), influenza viruses (9.9%), and human coronavirus (7.4%). Influenza virus, human parainfluenza viruses and human respiratory syncytial virus as well as human rhinovirus, human coronavirus and human metapneumovirus were detected significantly more frequently in LRTI patients than in controls. CONCLUSIONS: A bacterial pathogen is identified in approximately one in five adult patients with LRTI in primary care, and a viral pathogen in just under half, with mixed infections in one in ten. Penicillin-resistant pneumococci and ß-lactamase-producing H. influenzae are uncommon. These new findings support a restrictive approach to antibiotic prescribing for LRTI and the use of first-line, narrow-spectrum agents in primary care.

Management of community-acquired pneumonia in adults: 2016 guideline update from the Dutch Working Party on Antibiotic Policy (SWAB) and Dutch Association of Chest Physicians (NVALT).

The Dutch Working Party on Antibiotic Policy in collaboration with the Dutch Association of Chest Physicians, the Dutch Society for Intensive Care and the Dutch College of General Practitioners have updated their evidence-based guidelines on the diagnosis and treatment of community-acquired pneumonia (CAP) in adults who present to the hospital. This 2016 update focuses on new data on the aetiological and radiological diagnosis of CAP, severity classification methods, initial antibiotic treatment in patients with severe CAP and the role of adjunctive corticosteroids. Other parts overlap with the 2011 guideline. Apart from the Q fever outbreak in the Netherlands (2007-2010) no other shifts in the most common causative agents of CAP or in their resistance patterns were observed in the last five years. Low-dose CT scanning may ultimately replace the conventional chest X-ray; however, at present, there is insufficient evidence to advocate the use of CT scanning as the new standard in patients evaluated for CAP. A pneumococcal urine antigen test is now recommended for all patients presenting with severe CAP; a positive test result can help streamline therapy once clinical stability has been reached and no other pathogens have been detected. Coverage for atypical microorganisms is no longer recommended in empirical treatment of severe CAP in the non-intensive care setting. For these patients (with CURB-65 score >2 or Pneumonia Severity Index score of 5) empirical therapy with a 2nd/3rd generation cephalosporin is recommended, because of the relatively high incidence of Gram-negative bacteria, and to a lesser extent S. aureus. Corticosteroids are not recommended as adjunctive therapy for CAP.

Opinions of veterinarians on antimicrobial use in farm animals in Flanders and the Netherlands.

Veterinarians play an important role in the reduction of antimicrobial use in farm animals. This study aims to quantify opinions of veterinarians from the Netherlands and Flanders regarding antimicrobial use and resistance issues in farm animals. An online survey was sent out to 678 and 1100 farm animal veterinarians in Flanders and the Netherlands, of which 174 and 437 were returned respectively. Suboptimal climate conditions were regarded as the most important cause for high antimicrobial use in farm animals. Flemish veterinarians also regarded insufficient biosecurity measures and farmers' mentality as important determinants, while the Dutch respondents ranked insufficient immunity of young animals and economic considerations of farmers as major causes. The majority of Dutch respondents (63.8 per cent) supported the existing national policy, which aimed to halve veterinary antimicrobial use, while the Flemish (32.9 per cent) were less supportive of such a policy. Improvements in housing and climate conditions, biosecurity measures and strict control of specific infectious diseases were seen as important and promising measures to reduce antimicrobial use. To reduce antimicrobial use in farm animals, some shared approaches might be applicable in both countries. However, cultural, political and societal differences between Flanders and the Netherlands require differentiated approaches to reduce veterinary antimicrobial use.

Determinants associated with veterinary antimicrobial prescribing in farm animals in the Netherlands: a qualitative study.

Antimicrobial use in farm animals might contribute to the development of antimicrobial resistance in humans and animals, and there is an urgent need to reduce antimicrobial use in farm animals. Veterinarians are typically responsible for prescribing and overseeing antimicrobial use in animals. A thorough understanding of veterinarians' current prescribing practices and their reasons to prescribe antimicrobials might offer leads for interventions to reduce antimicrobial use in farm animals. This paper presents the results of a qualitative study of factors that influence prescribing behaviour of farm animal veterinarians. Semi-structured interviews with eleven farm animal veterinarians were conducted, which were taped, transcribed and iteratively analysed. This preliminary analysis was further discussed and refined in an expert meeting. A final conceptual model was derived from the analysis and sent to all the respondents for validation. Many conflicting interests are identifiable when it comes to antimicrobial prescribing by farm animal veterinarians. Belief in the professional obligation to alleviate animal suffering, financial dependency on clients, risk avoidance, shortcomings in advisory skills, financial barriers for structural veterinary herd health advisory services, lack of farmers' compliance to veterinary recommendations, public health interests, personal beliefs regarding the veterinary contribution to antimicrobial resistance and major economic powers are all influential determinants in antimicrobial prescribing behaviour of farm animal veterinarians. Interventions to change prescribing behaviour of farm animal veterinarians could address attitudes and advisory skills of veterinarians, as well as provide tools to deal with (perceived) pressure from farmers and advisors to prescribe antimicrobials. Additional (policy) measures could probably support farm animal veterinarians in acting as a more independent animal health consultant.

GRACE and the development of an education and training curriculum.

Antimicrobial resistance is a serious threat and compromises the management of infectious disease. This has particular significance in relation to infections of the respiratory tract, which are the lead cause of antibiotic prescribing. Education is fundamental to the correct use of antibiotics. A novel open access curriculum has been developed in the context of a European Union funded research project Genomics to combat Resistance against Antibiotics in Community-acquired lower respiratory tract infections in Europe (GRACE http://www.grace-lrti.org). The curriculum was developed in modular format and populated with clinical and scientific topics relevant to community-acquired lower respiratory tract infections. This curriculum informed the content of a series of postgraduate courses and workshops and permitted the creation of an open access e-Learning portal. A total of 153 presentations matching the topics within the curriculum together with slide material and handouts and 104 webcasts are available through the GRACE e-Learning portal, which is fully searchable using a 'mindmap' to navigate the contents. Metrics of access provided a means for assessing usage. The GRACE project has permitted the development of a unique on-line open access curriculum that comprehensively addresses the issues relevant to community-acquired lower respiratory tract infections and has provided a resource not only for personal learning, but also to support independent teaching activities such as lectures, workshops, seminars and course work.

SWAB/NVALT (Dutch Working Party on Antibiotic Policy and Dutch Association of Chest Physicians) guidelines on the management of community-acquired pneumonia in adults.

The Dutch Working Party on Antibiotic Policy (SWAB) and the Dutch Association of Chest Physicians (NVALT) convened a joint committee to develop evidence-based guidelines on the diagnosis and treatment of community acquired pneumonia (CAP). The guidelines are intended for adult patients with CAP who present at the hospital and are treated as outpatients as well as for hospitalised patients up to 72 hours after admission. Areas covered include current patterns of epidemiology and antibiotic resistance of causative agents of CAP in the Netherlands, the possibility to predict the causative agent of CAP on the basis of clinical data at first presentation, risk factors associated with specific pathogens, the importance of the severity of disease upon presentation for choice of initial treatment, the role of rapid diagnostic tests in treatment decisions, the optimal initial empiric treatment and treatment when a specific pathogen has been identified, the timeframe in which the first dose of antibiotics should be given, optimal duration of antibiotic treatment and antibiotic switch from the intravenous to the oral route. Additional recommendations are made on the role of radiological investigations in the diagnostic work-up of patients with a clinical suspicion of CAP, on the potential benefit of adjunctive immunotherapy, and on the policy for patients with parapneumonic effusions.

Diagnostic management of chronic obstructive pulmonary disease.

Detection of early chronic obstructive pulmonary disease (COPD) in patients presenting with respiratory symptoms is recommended; however, diagnosing COPD is difficult because a single gold standard is not available. The aim of this article is to review and interpret the existing evidence, theories and consensus on the individual parts of the diagnostic work-up for COPD. Relevant articles are discussed under the subheadings: history taking, physical examination, spirometry and additional lung function assessment. Wheezing, cough, phlegm and breathlessness on exertion are suggestive signs for COPD. The diagnostic value of the physical examination is limited, except for auscultated pulmonary wheezing or reduced breath sounds, increasing the probability of COPD. Spirometric airflow obstruction after bronchodilation, defined as a lowered ratio of the forced volume in one second to the forced vital capacity (FEV1/FVC ratio), is a prerequisite, but can only confirm COPD in combination with suggestive symptoms. Different thresholds are being recommended to define low FEV1/FVC, including a fixed threshold, and one varying with gender and age; however, the way physicians interpret these thresholds in their assessment is not well known. Body plethysmography allows a more complete assessment of pulmonary function, providing results on the total lung capacity and the residual volume and is indicated when conventional spirometry results are inconclusive. Chest radiography has no diagnostic value for COPD but is useful to exclude alternative diagnoses such as heart failure or lung cancer. Extensive history taking is of key importance in diagnosing COPD.

Trends in primary-care consultations, comorbidities, and antibiotic prescriptions for respiratory infections in The Netherlands before implementation of pneumococcal vaccines for infants.

The burden of respiratory infections is mainly seen in primary healthcare. To evaluate the potential impact of new preventive strategies against respiratory infections, such as the implementation of pneumococcal conjugate vaccines for infants in 2006 in The Netherlands, we conducted a baseline retrospective cohort study of electronic primary-care patient records to assess consultation rates, comorbidities and antibiotic prescription rates for respiratory infections in primary care. We found that between 1995 and 2005, overall registered consultation rates for lower respiratory tract infections had increased by 42·4%, upper respiratory infections declined by 4·9%, and otitis media remained unchanged. Concomitantly, there was a steady rise in overall comorbidity (75·7%) and antibiotic prescription rates (67·7%). Since Dutch primary-care rates for respiratory infections changed considerably between 1995 and 2005, these changes must be taken into account to properly evaluate the effect of population-based preventive strategies on primary-care utilization.

Predicting benign course and prolonged illness in lower respiratory tract infections: a 13 European country study.

BACKGROUND: Clinicians and patients are often uncertain about the likely clinical course of community-acquired lower respiratory tract infection (LRTI) in individual patients. We therefore set out to develop a prediction rule to identify patients at risk of prolonged illness and those with a benign course. METHODS: We determined which signs and symptoms predicted prolonged illness (moderately bad symptoms lasting >3 weeks after consultation) in 2690 adults presenting in primary care with LRTI in 13 European countries by using multilevel modelling. RESULTS: 212 (8.1%) patients experienced prolonged illness. Illness that had lasted >5 days at the time of presentation, >1 episode of cough in the preceding year, chronic use of inhaled pulmonary medication and diarrhoea independently predicted prolonged illness. Applying a rule based on these four variables, 3% of the patients with ≤ 1 variable present (n = 955, 37%) had prolonged illness. Patients with all four variables present had a 30% chance of prolonged illness (n = 71, 3%). CONCLUSIONS: Most patients with acute cough (>90%) recover within 3 weeks. A prediction rule containing four clinical items had predictive value for the risk of prolonged illness, but given its imprecision, appeared to have little clinical utility. Patients should be reassured that they are most likely to recover within three weeks and advised to re-consult if their symptoms persist beyond that period.

Rapid early weight gain is associated with wheeze and reduced lung function in childhood.

The aim of our study was to investigate the association between rapid weight gain in the first 3 months of life and the prevalence of wheeze in the first years of life and lung function at 5 yrs of age. The infants selected were participating in an ongoing birth cohort. Information on growth and respiratory symptoms was collected during the first year of life, and on primary care consultations during total follow-up. Forced expiratory volume in 1 s (FEV(1)) and forced expiratory flow at 25-75% of forced vital capacity (FEF(25-75%)) were measured at 5 yrs of age. Information on growth and respiratory symptoms was obtained for 1,431 infants, out of whom 235 children had already had 5 yrs of follow-up. Every one-point z-score increase in weight gain resulted in a 37% increase in days with wheeze (incidence rate ratio 1.37, 95% CI 1.27-1.47; p<0.001) and in associated consultations by 16% (incidence rate ratio 1.16, 95% CI 1.01-1.34; p=0.04). Children with rapid weight gain reported significantly more physician-diagnosed asthma. FEV(1) and FEF(25-75%) were reduced by 34 mL (adjusted regression coefficient -0.034, 95% CI -0.056- -0.013; p=0.002) and 82 mL (adjusted regression coefficient -0.082, 95% CI -0.140- -0.024; p=0.006) per every one-point z-score increase in weight gain, respectively. These associations were independent of birthweight. Rapid early weight gain is a risk factor for clinically relevant wheezing illnesses in the first years of life and lower lung function in childhood.

Guidelines for the management of adult lower respiratory tract infections--summary.

This document is an update of Guidelines published in 2005 and now includes scientific publications through to May 2010. It provides evidence-based recommendations for the most common management questions occurring in routine clinical practice in the management of adult patients with LRTI. Topics include management outside hospital, management inside hospital (including community-acquired pneumonia (CAP), acute exacerbations of COPD (AECOPD), acute exacerbations of bronchiectasis) and prevention. The target audience for the Guideline is thus all those whose routine practice includes the management of adult LRTI.

Guidelines for the management of adult lower respiratory tract infections--full version.

This document is an update of Guidelines published in 2005 and now includes scientific publications through to May 2010. It provides evidence-based recommendations for the most common management questions occurring in routine clinical practice in the management of adult patients with LRTI. Topics include management outside hospital, management inside hospital (including community-acquired pneumonia (CAP), acute exacerbations of COPD (AECOPD), acute exacerbations of bronchiectasis) and prevention. Background sections and graded evidence tables are also included. The target audience for the Guideline is thus all those whose routine practice includes the management of adult LRTI.

Relationship between parental lung function and their children's lung function early in life.

This study investigated the relationship between parental lung function and their children's lung function measured early in life. Infants were participants in the Wheezing Illnesses Study Leidsche Rijn (WHISTLER). Lung function was measured before the age of 2 months using the single occlusion technique. Parental data on lung function (spirometry), medical history and environmental factors were obtained from the linked database of the Utrecht Health Project. Parental data on pulmonary function and covariates were available in 546 infants. Univariate linear regression analysis demonstrated a significant positive relationship between the infant's respiratory compliance and parental forced expiratory flow at 25-75% of forced vital capacity (FEF(25-75%))(,) forced expiratory volume in 1 s (FEV(1)) and forced vital capacity. A significant negative relationship was found between the infant's respiratory resistance and parental FEF(25-75%)and FEV(1). No significant relationship was found between the infant's respiratory time constant and parental lung function. Adjusting for body size partially reduced the significance of the observed relationship; adjusting for shared environmental factors did not change the observed results. Parental lung function levels are predictors of the respiratory mechanics of their newborn infants, which can only partially be explained by familial aggregation of body size. This suggests genetic mechanisms in familial aggregation of lung function, which are already detectable early in life.

The impact of using different symptom-based exacerbation algorithms in patients with COPD.

Not all exacerbations are captured by reliance on healthcare contacts. Symptom-based exacerbation definitions have shown to provide more adequate measures of exacerbation rates, severity and duration. However, no consensus has been reached on what is the most useful method and algorithm to identify these events. This article provides an overview of the existing symptom-based definitions and tests the hypothesis that differences in exacerbation characteristics depend on the algorithms used. We systematically reviewed symptom-based methods and algorithms used in the literature, and quantified the impact of the four most referenced algorithms on exacerbation-related outcome using an existing chronic obstructive pulmonary disease (COPD) cohort (n = 137). We identified 51 studies meeting our criteria using 14 widely varying symptom algorithms to define onset, severity and recovery. The most (71%) frequently referenced algorithm (modified Anthonisen) identified an incidence rate of 1.7 episodes·patient-yr⁻¹ (95% CI 1.4-2.1), while for requiring only one major or two major symptoms this was 1.9 episodes·patient-yr⁻¹ (95% CI 1.6-2.3) and 1.5 episodes·patient-yr⁻¹ (95% CI 0.6-1.0), respectively. Studies were generally lacking methods to enhance validity and accuracy of symptom recording. This review revealed large inconsistencies in definitions, methods and accuracy to define symptom-based COPD exacerbations. We demonstrated that minor changes in symptom criteria substantially affect incidence rates, clustering type and classification of exacerbations.