Abstract
Objective: The aim of this study was to assess the utility of family physicians’ office spirometry, to detect previously undiagnosed chronic obstructive pulmonary disease (COPD) in individuals who smoke. Furthermore, agreement between doctors with more or less experience in performing spirometry was assessed. Methods: Cross-sectional study. Smokers aged 40–69 years who attended a family practice centre were invited to participate. Variables considered were tobacco pack-years, time of tobacco use, smoking cessation, COPD symptoms, Medical Research Council Dyspnoea Scale values, pre- and post-bronchodilator spirometry data, and acceptability of spirometry curves. Results: 212 subjects underwent spirometry, and 179 yielded acceptable spirometry curves. Of these, 173 subjects underwent reversibility testing, of whom 39 (22.5%, 95% CI: 16.2–29.1%) were diagnosed as COPD. Of these, 48.7% were classified as COPD Stage I and 41.0% as Stage II following GOLD criteria. Age, gender, pack-years and cough were related to airflow obstruction levels. Symptom number was not related to presence of airflow obstruction. More than 80% of spirometry curves were acceptable. Agreement on curve acceptability between junior doctors and a family physician trainer was very good, but moderate between junior doctors and a pulmonologist.
Conclusions: Forced spirometry data from smokers attending general practice doctors can be used to identify a significant number of previously undiagnosed COPD cases.
Introduction
Chronic obstructive pulmonary disease (COPD) is an important health problem owing to its high prevalence and high morbidity and mortality rates (Citation1). Currently, COPD is considered the fourth cause of death in the developed world, and is the only cause of death that continues to increase in frequency (Citation2).
According to figures from the year 2000, the prevalence of COPD in Spanish subjects aged 40–69 years was 9.1%, with this figure increasing to 13.2% in individuals who smoke. In men aged more than 60 years, and in smokers of more than 30 pack-years, the prevalence increased to 40% (Citation3). It is estimated that approximately 20% of all smokers will develop the disease (Citation4). In Spain, COPD is responsible for 10–12% of all primary care consultations with family doctors. Moreover, COPD is the cause of 7% of all hospital admissions (Citation5). Annual total cost of the disease in Spain amounted to 451676884€; with a cost/person/year of 1673€ (Citation6).
COPD is characterized by airflow obstruction, is generally progressive, and is not completely reversible (Citation7). Though several environmental risk factors for COPD have been recognized (air pollution, biomass), tobacco addiction is still a major risk factor and causes a huge number of COPD cases (Citation1). The single most effective measure to slow disease progression is smoking cessation (Citation8).
With 75% of cases remaining undetected, COPD is clearly an under diagnosed disease (Citation3,Citation5,Citation9). Patients fail to visit their doctors until they have symptoms such as exertion dyspnoea that affects quality of life. Patients often attribute symptoms such as coughing and productive sputum (which appear earlier) to the smoking habit per se (Citation10,Citation11). Early diagnosis would allow introduction of adequate preventive and therapeutic measures to slow the irreversible loss of lung function, thus improving long-term disease prognosis (Citation10,Citation11).
Forced spirometry is the main COPD diagnostic procedure (Citation12). It is a relatively simple, non-invasive, and low-cost test (approximately 30€ per procedure in Spain). These characteristics make forced spirometry a suitable diagnostic tool in the primary care setting. Approximately half of all family doctors in Spain have spirometers in their primary care centres. However, the use of forced spirometry in primary care is limited because many family physicians do not know how to perform spirometry tests, and test quality standards are thus poor. Indeed, 38% of patients diagnosed with COPD in primary care centres have never undergone spirometry (Citation13).
Few studies have investigated detection of previously undiagnosed COPD in Spanish primary care centres. We therefore evaluated the use of full spirometry with bronchodilator test to improve COPD diagnoses in a Spanish family practice, and we assessed the information provided by spirometry curves and the interpretation given by junior doctors.
Methods
Study design
This is a descriptive cross-sectional study undertaken in a teaching primary care centre in Palma, a town on Majorca (one of the Balearic Islands), with 15 family doctors and a practice catchment's population of 26 000 patients. The study protocol was approved by the Primary Care Research Committee.
Study subjects
Sample size was calculated assuming a COPD under diagnosis of 4.8% (Citation3), a 5% alpha error, and a precision of 3%. A sample of 211 individuals was required. Subjects were a convenient sample of smokers who visited their family doctors during a period of three months. Participants were asked at random to participate and the first 212, who met the criteria and gave their consent, were included. Exclusion criteria were: known diagnosis of asthma, COPD, or other pulmonary disease; use of inhaler medication; spirometry testing within the last 12 months; concurrent illnesses that contraindicated spirometry; and presence of mental or physical disabilities that might affect spirometry data. Patients who made appointments with their family doctors, who fulfilled the criteria and signed informed consent, were included. Follow-up appointments were scheduled for spirometry in conjunction with personal interviews. The average duration of each spirometry test and associated interview was 50 min.
Measurement criteria and equipment
Spirometry. Forced spirometry tests were performed using a DATOSPIR 120 Sibel® spirometer. The bronchodilator response (BDR) was measured using a single 200 microgram dose of inhaled salbutamol; spirometry was performed 20 min later. A BDR was considered positive if the proportion of change between pre and post bronchodilator forced expiratory volume (FEV1) was greater than 12% and at least 200 ml in absolute values. Spirometry curves were assessed using Spanish Society of Respiratory Diseases (SEPAR) criteria (Citation5).
The following spirometry parameters were evaluated: FEV1; FVC; FEV1/FVC; and spirometry pattern (obstructive, non-obstructive, or normal). Further variables considered were test duration; number of test attempts; level of patient collaboration (good, fair, poor); reported problems while performing the test; diagnoses of COPD was made with reference to GOLD criteria (Citation7) in patients with post BDR FEV1/FVC ratios <70%.
All spirometry tests (212) were monitored and controlled by three family medicine doctors who were undertaking specialist training (the ‘trainees’) and all received adequate instruction. All spirometry tests were supervised by a senior trainer of family doctors (the ‘trainer’) to evaluate reliability and validity. The trainer's supervision was used as the validity criterion. At a later stage, a random sample of 49 spirometry tests was selected to measure agreement with evaluations made by a pulmonologist.
Questionnaire. Employment status, tobacco consumption, and tobacco quitting stage were evaluated, using a questionnaire validated by Torrecilla (Citation14). Respiratory variables such as the presence of respiratory symptoms (cough, wheeze and sputum) and breathlessness according to the Medical Research Council scale (five items), (Citation15) and family history of COPD were also included in analysis.
Statistical analysis
Statistical analysis was performed using SPSS version 11.5 software. The Chi-square test was used to compare qualitative variables and Student's t-test was employed for quantitative analysis. To assess the diagnostic value of the pack-years and the presence of respiratory symptoms in COPD diagnosis, we calculated sensitivity, specificity, positive and negative predictive values and positive and negative likelihood ratios. Simple agreement and the Kappa Index were used to estimate diagnostic agreement between the trainees, the trainer, and a pulmonologist.
Results
Population characteristics
Forced spirometry data were obtained from 212 patients. Of these, 179 spirometry datasets (84.4%) were valid, and BDR data were obtained from 173 subjects. These 173 subjects with complete data are those included for the present analysis. Mean subject age was 50 ± 7.8 years. Slightly more than half the subjects (52.3%) were male. Employed subjects comprised 69.5% of the total, 12.3% were unemployed, and 10.8% were retired. About 64% of subjects had some degree of (usually mild) dyspnoea. Among 173 subjects, 21.7% reported a family history of COPD, and 83.4% thought that smoking was affecting their lungs.
Subjects smoked an average of 28.42 ± 18.30 pack-years and a median of 25.8 pack-years. A total of 77.1% of men and 51.5% of women (P <0.001) smoked more than 20 pack-years. By age group, 80.6% of those aged more than 60 years smoked more than 20 pack-years. Corresponding proportions in those aged 50–59 years and 40–49 years were 67.6% and 57.4%, respectively.
Spirometry results
summarizes the spirometry and post-BDR data. 39 new COPD cases were diagnosed. Thus, COPD was diagnosed in 22.5% (95% CI: 16.02–29.05) of subjects from whom valid spirometry data were obtained. ‘Other’ subjects included those whose test results were difficult to interpret owing to low FVC values. More than 90% of detected COPD cases were classed as Stages I (19 cases; 48.7%) and II (16 cases; 41.0%). Only four cases (10.3%) of Stage III COPD (FEV1<50%) were diagnosed.
Table I. Spirometry results.
Agreement in spirometry curve assessment () was very good between the trainees and the trainer; good between the trainer and the pulmonologist; and moderate between the trainees and the pulmonologist.
Table II. Between-observer agreement in spirometry curve assessment.
Characteristics of COPD patients
As shown in , COPD prevalence was higher in men and the prevalence of chronic obstruction significantly increased by age. Of the symptoms analysed, only coughing was more prevalent in COPD patients than in those without COPD. No statistically significant differences were found between patients with no symptoms, a single symptom, and two or three concurrent symptoms.
Table III. Socio-demographic and clinical characteristics of patients according to COPD diagnosis.
shows that presence of respiratory symptoms (cough, sputum, wheeze) and pack-years showed relatively low diagnostic validity
Table IV. Parameters validating COPD diagnosis include pack-years and respiratory symptoms.
Discussion
Few studies have investigated detection of previously undiagnosed COPD in Spanish primary care centres. Acquisition of forced spirometry data from smokers attending a family doctor practice allows detection of a considerable number of undiagnosed COPD cases. Up to 22.5% of smoking patients aged more than 40 years not previously diagnosed and attending a primary care doctor for any reason, had COPD according to GOLD criteria. Thus, one COPD case was diagnosed for every four spirometry tests performed.
Limitations
This study presents several limitations. First of all, we are not able to give pre-study prevalence of COPD in the health centre. COPD diagnosis in Majorca Primary Health Care Area is under registered in the computerized clinical records. District Performance Indicators had shown that COPD prevalence is lower than expected in all health centres. Second, since a random sampling was used, results are not fully representative of COPD in the smoker's population. It can result in overestimation of COPD if family doctors have invited the most symptomatic patients. Moreover, the results of our study are based on spirometry diagnosed COPD without taking into consideration the presence and persistence of COPD symptoms. In fact, without patient follow up and repeated pulmonary function measurements, confirmed presence of COPD in smokers may be overestimated. Actually it would be more appropriate to use the term ‘patients at high risk of developing chronic pulmonary disease’ used by van Schayck et al. (Citation16). Finally, data of those excluded to the study has not been registered.
Interpretation of findings
The prevalence of previously undiagnosed COPD seen in our study approximates frequencies seen in similar studies using the GOLD classification (Citation17–20). Other reports using different patient selection and COPD classification criteria yielded rather different results, with COPD diagnosis levels of 9–29% (Citation9,Citation16,Citation21–25).
As in other studies, age, male gender, and pack-years were associated with COPD incidence (Citation21,Citation24). Age is one of the most important predictors of COPD. Other studies have described a high percentage of airflow obstruction in the group of 61–70 year old primary care patients (Citation16). This can be attributed both to greater tobacco exposure in older males and to the physiological pulmonary function decline occurred by age.
Performance of spirometry on patients who attend consultations for reasons unrelated to COPD allows mild and moderate COPD cases to be detected (Citation19,Citation21,Citation16). In the study of Stratelis and co-workers, (Citation18) up to 85% of patients were affected by mild COPD, possibly because younger individuals (aged 40–55 years) were included in the study. In our study, almost half (48.7%) of all subjects diagnosed with COPD had Stage I disease, and 42% had Stage II disease. A key feature of our study is the high proportion of young COPD subjects who would otherwise have remained undiagnosed until symptoms were more advanced. It is quite possible that older patients affected by severe COPD had been diagnosed previously. Effective case finding could increase if only smokers of 60 years and older are offered spirometry by increasing positive predictive value and sensitivity. However, the detection of non-symptomatic young patients with early COPD offers the possibilities of long-term follow-up and delivery of optimal therapeutic measures, mostly intervention strategies to assist in smoking cessation.
Several methods to improve the ability of spirometry to detect COPD have been proposed. Questionnaires seeking reliable diagnosis of COPD on the basis of reported respiratory symptoms are not widely validated, and seem unable to improve spirometry sensitivity. In agreement with other studies (Citation17–18,Citation22,Citation26), we found that respiratory symptoms were no greater in COPD smokers than in smokers without COPD. The likelihood ratios of respiratory symptoms presence were near unity, consequently their presence would not increase the post-test COPD diagnosis. Stratelis suggested that spirometry would be performed for patients who have smoked more than 30 pack-years, without consideration of symptoms (Citation21). However, our results show that this cut-off point would not increase spirometry diagnostic value because both negative and positive likelihood ratios were close to unity.
Our results indicate that BDR test assists in better patient diagnosis and classification when obstruction is present. In this study probable diagnosis of asthma has been detected in 10% of those with airflow obstruction who otherwise would have been overdiagnosed as COPD, which is previously described by others (Citation18). In terms of an efficient case-finding strategy, to perform reversibility tests may not be helpful as provide scarce additional information (5% of patients with normal airflow have been identified at risk of developing asthma). Moreover, it is time-consuming, taking 10–15 min per subject and largely increasing the cost of the test. These findings suggest that BDR could be more useful in those individuals that fulfil GOLD obstructive criteria in the pre-bronchodilator results and could be considered the best option for case-finding.
More than 80% of the spirometry curves of our study were of good quality, as assessed by SEPAR criteria. As recent reports have shown, spirometry performance in the primary care setting has improved (Citation22,Citation26,Citation28,Citation29) and results are now similar to those obtained in hospital settings. This may be due to improved skills in the primary care setting, increased training, and proper instrument calibration (Citation28–32). Between-observer agreement in spirometry curve assessment was considered either good or moderate. The fact that concordance was better between the trainer and the pulmonologist (compared with trainee and pulmonologist) possibly reflects the relative experience levels of the doctors involved in this study. It is difficult to compare our reproducibility parameters with those of other reports owing to differences in study design and parameters evaluated. Akhar and Wilson (Citation33) obtained a moderate level of agreement when data from spirometry performed in primary care were compared with data obtained in a lung function laboratory (Kappa 0.46). We did not assess reproducibility of quantitative parameters as other authors have done (Citation22,Citation28,Citation29).
Conclusions
Our results show that using spirometry in smokers in primary care would detect substantial number of undiagnosed COPD cases. It is a feasible technology provided some prerequisites are met. Adequate spirometry performance and interpretation training is required, the instrument must be properly maintained, and test procedures must be standardized (Citation34). This work adds a new perspective to the current debate about the recommendation for spirometry for COPD early diagnosis in primary care by using a current practice approach and by introducing reversibility test to discriminate possible asthma misdiagnosis only when the obstruction is present.
Acknowledgments
The authors thank Teresa Piqué, Miguel Angel Vicente, Eugenia Carandell, Rosa Robles, Juli Fuster, Mercé García, and Montse Llort, all family doctors of Son Pisà Health Center, for their collaboration. We are grateful to Ana Uréndez and Tina Crespí for supporting junior doctors in their use of spirometry. We thank Dr Bernad Togores, pneumologist at the Hospital Son Dureta, for his suggestions during the study. In addition, the authors wish to acknowledge Dr Alvar Agustí and Dr Joan Soriano of the Caubet-Cimera Foundation for Research on Respiratory Diseases. This study received support from the University Institute of Health Sciences of the Illes Balears University (IUNICS).
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
Related Research Data
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