copd is a common , usually progressive disease characterized by chronic inflammation of the airways and persistent airflow limitation .
its prevalence is increasing worldwide , and it is expected to be the third largest global cause of mortality by the year 2030.1 in japan , a large epidemiological study ( the nippon copd epidemiological study ) reported that the prevalence of airflow limitation was 10.6% , and at least 8.6% of subjects were sought to have copd.2 several studies have shown that the prevalence of potentially undiagnosed airflow limitation in both western35 and asian6 countries is ~ 3%15% .
many patients with copd continue to be underdiagnosed and untreated.2,7 since copd is a preventable and treatable disease , the importance of early detection has been emphasized.8 the use of simple copd screening questionnaires to detect persistent airflow limitation may help in the early diagnosis of copd .
these tools reliably detect airflow limitation in the general population and may facilitate the early , accurate diagnosis of copd in general practice settings.9,10 some copd diagnostic questionnaires have already been reported.1114 the copd population screener ( copd - ps ) , which was developed by a clinician working group in the united states , is a five - item , self - administered questionnaire that was validated for screening individuals in the general population who are at high risk of copd .
it is composed of three copd - related items ( breathlessness , productive cough , and activity limitation ) and one question , each regarding smoking history and age.15 in a previous population - based study , we verified the validity of the japanese version of the copd - ps questionnaire for the identification of individuals at increased risk of airflow limitation.16 this instrument is easy to score and would be suitable for large - scale screening of possible airflow obstruction ( ao ) .
another copd screening tool , the international primary care airway group ( ipag ) questionnaire,11 is in use worldwide .
it consists of eight items and takes more time to administer than the copd - ps questionnaire .
the purpose of this study was to compare these two questionnaires in the general japanese population , as no previous research has done so , as well as to assess the ability of both instruments to discriminate between subjects with and without persistent ao .
this study was based on data from the hisayama study , which is an ongoing population - based epidemiologic study designed to investigate the morbidity , mortality , and risk factors of cardiovascular and smoking - related diseases in the town of hisayama , japan .
the town is located in a suburban area adjacent to fukuoka city , a large urban center on kyushu island in the southern part of japan .
the population of the town is ~8,000 and has been stable for over 50 years .
according to national census data , the distributions of age and occupations in hisayama have been almost identical to those across japan since the 1960s.17 this cross - sectional study compared the screening efficacy of the copd - ps and ipag questionnaires in copd patients . in 2012 ,
registered subjects 40 years of age and older were solicited to participate in a town - wide health checkup that included spirometry . of the 2,643 subjects who were enrolled between june 2012 and october 2012 ,
307 were excluded for the following reasons : 105 had physician - diagnosed asthma , 22 had a previous lung resection , 159 had poor studied data , and 21 had records with missing data .
the final analysis included data for 2,336 subjects with fully completed copd - ps and ipag questionnaires and valid spirometry measurements .
the subjects who provided informed consent to participate in the health checkup independently completed the japanese versions of the copd - ps and ipag questionnaires , and then , in addition to their usual clinical tests , underwent spirometry using a chestgraph hi-105 spirometer ( chest mi , tokyo , japan ) .
each subject performed at least three forced vital capacity ( fvc ) maneuvers according to the recommended method .
the results were assessed by two pulmonary physicians , who visually inspected the flow  volume curve and excluded subjects without at least two satisfactory tests .
the highest forced expiratory volume in 1 second ( fev1 ) and fvc values were used for analysis .
the subjects who had pre - bronchodilator ( bd ) fev1/fvc < 0.70 were eligible for post - bd testing , in which spirometry was performed 15 minutes after inhalation of salbutamol ( glaxosmithkline , tokyo , japan ) via a metered - dose inhaler with a spacer , according to the procedure recommended.18 persistent ao was defined as having a post - bd fev1/fvc < 0.70 . the subjects with persistent ao were categorized according to the global initiative for chronic obstructive lung disease criteria ( mild , fev1 80% predicted ; moderate , 50% fev1 < 80% predicted ; severe , 30% fev1 < 50% predicted ; very severe , fev1
< 30% predicted).19 the study protocol was approved by the institutional review board for clinical research of kyushu university ( numbers 2137 , 2482 , and 24123 ) and of kagoshima university ( numbers 156 and 279 ) , and all subjects provided their written informed consent prior to participation in the study .
the copd - ps is a brief , reliable , self - scored questionnaire to identify individuals likely to have copd .
it consists of five items , three assessing copd - related symptoms on a 5-point scale , one on cigarette use ( 3-point scale ) , and one on the subject s age ( four categories ) .
these five items are scored 0 , 1 , or 2 with a summed total score ranging from 0 to 10 . in the japanese version of the copd - ps questionnaire , a cutoff point of 4
has been found to be useful for copd screening.16 the ipag questionnaire is also a self - scored questionnaire and has been validated in smokers as a screening tool for copd diagnosis.11 the ipag questionnaire is composed of eight items : one on the subject s age ( four categories ) , one on body mass index ( 3-point scale ) , one on cigarette use ( 4-point scale ) , and five on symptoms / history ( 2- or 3-point scales ) .
each question is scored individually , with a summed total score ranging from 0 to 38 .
a suggested cutoff score of 17 is used for smokers in general health checkup settings and general practices in japan . however , there is no cutoff score for persistent ao in the general japanese population , including never - smokers , and we therefore investigated this issue in this study .
baseline data for the demographic characteristics of the study population and the informant questionnaires were evaluated in descriptive analyses . the kruskal 
spearman correlations were used to examine the strength of associations between informant and performance measures . for the subjects who used a bd ,
another way to evaluate the utility of screening tests is with the likelihood ratio;20 likelihood ratios range from 0 to infinity ; larger numbers provide more convincing evidence of a disease , smaller numbers indicate that the disease is less likely , and ratios close to one lack diagnostic value .
likelihood ratios ( positive and negative ) were calculated for both the copd - ps and the ipag questionnaires .
receiver operating characteristic ( roc ) curves and areas under the roc curves ( aucs ) were generated to reflect graphically and quantitatively the ability of the copd - ps and the ipag questionnaires to discriminate between subjects with and without persistent ao using the delong method.21 another method proposed by pencina et al22 was also utilized for this purpose ; this approach assesses the ability of a model to reclassify case and control subjects , respectively , on the basis of the individual - estimated probability of an event .
the ability of the model to reclassify is summarized by the net reclassification improvement ( nri ) and integrated discrimination improvement ( idi ) .
we defined four strata dividing the risk of persistent ao into four quartiles , namely , q1 , q2 , q3 , and q4 .
the nri considers only the changes in the estimated prediction probabilities that imply a change from one category to another .
in contrast , the idi does not require a prior definition of strata risk and considers the change in the estimation prediction probabilities as a continuous variable .
we computed the nri and idi and examined the accuracy of the two screening questionnaires in diagnosing ao .
all statistical analyses were performed using r version 3.1.0.23 the results were considered statistically significant when p<0.05 .
this study was based on data from the hisayama study , which is an ongoing population - based epidemiologic study designed to investigate the morbidity , mortality , and risk factors of cardiovascular and smoking - related diseases in the town of hisayama , japan .
the town is located in a suburban area adjacent to fukuoka city , a large urban center on kyushu island in the southern part of japan .
the population of the town is ~8,000 and has been stable for over 50 years .
according to national census data , the distributions of age and occupations in hisayama have been almost identical to those across japan since the 1960s.17
this cross - sectional study compared the screening efficacy of the copd - ps and ipag questionnaires in copd patients . in 2012 , registered subjects 40 years of age and older were solicited to participate in a town - wide health checkup that included spirometry .
of the 2,643 subjects who were enrolled between june 2012 and october 2012 , 307 were excluded for the following reasons : 105 had physician - diagnosed asthma , 22 had a previous lung resection , 159 had poor studied data , and 21 had records with missing data .
the final analysis included data for 2,336 subjects with fully completed copd - ps and ipag questionnaires and valid spirometry measurements .
the subjects who provided informed consent to participate in the health checkup independently completed the japanese versions of the copd - ps and ipag questionnaires , and then , in addition to their usual clinical tests , underwent spirometry using a chestgraph hi-105 spirometer ( chest mi , tokyo , japan ) .
each subject performed at least three forced vital capacity ( fvc ) maneuvers according to the recommended method .
the results were assessed by two pulmonary physicians , who visually inspected the flow  volume curve and excluded subjects without at least two satisfactory tests .
the highest forced expiratory volume in 1 second ( fev1 ) and fvc values were used for analysis .
the subjects who had pre - bronchodilator ( bd ) fev1/fvc < 0.70 were eligible for post - bd testing , in which spirometry was performed 15 minutes after inhalation of salbutamol ( glaxosmithkline , tokyo , japan ) via a metered - dose inhaler with a spacer , according to the procedure recommended.18 persistent ao was defined as having a post - bd fev1/fvc < 0.70 .
the subjects with persistent ao were categorized according to the global initiative for chronic obstructive lung disease criteria ( mild , fev1 80% predicted ; moderate , 50% fev1 < 80% predicted ; severe , 30% fev1 < 50% predicted ; very severe , fev1 < 30% predicted).19 the study protocol was approved by the institutional review board for clinical research of kyushu university ( numbers 2137 , 2482 , and 24123 ) and of kagoshima university ( numbers 156 and 279 ) , and all subjects provided their written informed consent prior to participation in the study .
the copd - ps is a brief , reliable , self - scored questionnaire to identify individuals likely to have copd .
it consists of five items , three assessing copd - related symptoms on a 5-point scale , one on cigarette use ( 3-point scale ) , and one on the subject s age ( four categories ) .
these five items are scored 0 , 1 , or 2 with a summed total score ranging from 0 to 10 . in the japanese version of the copd - ps questionnaire ,
the ipag questionnaire is also a self - scored questionnaire and has been validated in smokers as a screening tool for copd diagnosis.11 the ipag questionnaire is composed of eight items : one on the subject s age ( four categories ) , one on body mass index ( 3-point scale ) , one on cigarette use ( 4-point scale ) , and five on symptoms / history ( 2- or 3-point scales ) .
each question is scored individually , with a summed total score ranging from 0 to 38 .
a suggested cutoff score of 17 is used for smokers in general health checkup settings and general practices in japan .
however , there is no cutoff score for persistent ao in the general japanese population , including never - smokers , and we therefore investigated this issue in this study .
baseline data for the demographic characteristics of the study population and the informant questionnaires were evaluated in descriptive analyses . the kruskal 
spearman correlations were used to examine the strength of associations between informant and performance measures . for the subjects who used a bd ,
another way to evaluate the utility of screening tests is with the likelihood ratio;20 likelihood ratios range from 0 to infinity ; larger numbers provide more convincing evidence of a disease , smaller numbers indicate that the disease is less likely , and ratios close to one lack diagnostic value .
likelihood ratios ( positive and negative ) were calculated for both the copd - ps and the ipag questionnaires .
receiver operating characteristic ( roc ) curves and areas under the roc curves ( aucs ) were generated to reflect graphically and quantitatively the ability of the copd - ps and the ipag questionnaires to discriminate between subjects with and without persistent ao using the delong method.21 another method proposed by pencina et al22 was also utilized for this purpose ; this approach assesses the ability of a model to reclassify case and control subjects , respectively , on the basis of the individual - estimated probability of an event .
the ability of the model to reclassify is summarized by the net reclassification improvement ( nri ) and integrated discrimination improvement ( idi ) .
we defined four strata dividing the risk of persistent ao into four quartiles , namely , q1 , q2 , q3 , and q4 .
the nri considers only the changes in the estimated prediction probabilities that imply a change from one category to another .
in contrast , the idi does not require a prior definition of strata risk and considers the change in the estimation prediction probabilities as a continuous variable .
we computed the nri and idi and examined the accuracy of the two screening questionnaires in diagnosing ao .
all statistical analyses were performed using r version 3.1.0.23 the results were considered statistically significant when p<0.05 .
the baseline characteristics of the 2,336 subjects stratified by airflow limitation category following post - bd spirometry are presented in table 1 .
the majority of subjects ( 88.9% ) showed an initial fev1/fvc 0.70 . following post - bd spirometry ,
almost all the ao subjects ( 94.0% ) were classified as having mild or moderate copd ; only 6.0% of the ao subjects had severe or very severe copd .
the ao subjects were older , were more likely to be men , had lower body mass index , had a higher number of pack - years smoked , and were more likely to be former or current smokers ( table 1 ) . the mean and
for the ao and non - ao subjects , respectively , the mean scores were 3.9 and 2.4 , while the median scores were 4 and 2 .
the ipag and the copd - ps questionnaires were correlated with fev1/fvc ( r=0.356 and r=0.301 , respectively , p<0.001 ) , and the two questionnaires correlated with each other ( r=0.622 , p<0.001 ; table 2 ) . the previously identified cutoff point of 4 was used for the copd - ps questionnaire .
the crude odds ratio ( or ) of the copd - ps questionnaire for ao was 5.52 , and the sensitivity of copd - ps questionnaire was 66.7% and the specificity was 73.4% .
in this population - based study that included never - smokers , a cutoff point of 20 on the ipag questionnaire would be adequate for screening for ao ( table 3 ) .
the crude or of the ipag questionnaire for ao , using a cutoff point of 20 , was 6.56 .
if a cutoff point of 17 was used on the ipag questionnaire , the sensitivity was higher ( 86.0% ) but both the specificity and auc were much lower , 46.2% and 0.66% , respectively .
if a cutoff point of 20 was used instead of 17 , the sensitivity was slightly lower ( 71.3% ) but both the specificity and auc were higher , 75.2% and 0.72% , respectively .
roc curves were generated to measure the properties of the copd - ps and the ipag questionnaires in discriminating subjects without ao from those with ao .
the auc values obtained from the roc curve by discriminating ao from no ao were 0.747 ( 95% confidence interval [ ci ] , 0.7070.788 ) for the copd - ps questionnaire and 0.775 ( 95% ci , 0.7350.816 ) for the ipag questionnaire ( figure 1 ) .
there was no significant difference in the auc values with the two questionnaires ( p=0.09 ) . between the copd - ps and ipag questionnaires ,
no statistically significant differences were founded in terms of sensitivity , specificity , or positive and negative predictive values .
however , compared with the copd - ps questionnaire , the ipag questionnaire had superior likelihood ratios for both a positive ( 2.51 vs 2.59 ) and negative test ( 0.45 vs 0.40 ) , with nonoverlapping cis ( table 4 ) .
reclassifications of subjects with and without ao are summarized in table 5 . for 672 ( 30.7% ) subjects without ao ,
classification improved using the model with the copd - ps questionnaire , and for 549 ( 25.1% ) subjects , it became worse , with the net gain in reclassification proportion of 0.056 . for subjects with ao
, classification was improved in 21 subjects ( 14.0% ) and less accurate in 28 subjects ( 18.7% ) , with the net gain in reclassification proportion of 0.047 .
thus , the categorical nri was 0.0096 ( 95% ci , 0.08680.106 ; p=0.845 ) .
the continuous nri and idi for predicting the presence of ao using the model with the copd - ps questionnaire against the ipag questionnaire were 0.107 ( 95% ci , 0.2730.058 ; p=0.203 ) and 0.014 ( 95% ci , 0.0330.006 ; p=0.182 ) , respectively , and these were not statistically significant ( table 5 ) .
the copd - ps and the ipag questionnaires had only a marginal difference in their ability to discriminate between the subjects with and without ao .
the baseline characteristics of the 2,336 subjects stratified by airflow limitation category following post - bd spirometry are presented in table 1 .
the majority of subjects ( 88.9% ) showed an initial fev1/fvc 0.70 . following post - bd spirometry ,
almost all the ao subjects ( 94.0% ) were classified as having mild or moderate copd ; only 6.0% of the ao subjects had severe or very severe copd .
the ao subjects were older , were more likely to be men , had lower body mass index , had a higher number of pack - years smoked , and were more likely to be former or current smokers ( table 1 ) . the mean and
for the ao and non - ao subjects , respectively , the mean scores were 3.9 and 2.4 , while the median scores were 4 and 2 .
the ipag and the copd - ps questionnaires were correlated with fev1/fvc ( r=0.356 and r=0.301 , respectively , p<0.001 ) , and the two questionnaires correlated with each other ( r=0.622 , p<0.001 ; table 2 ) .
the previously identified cutoff point of 4 was used for the copd - ps questionnaire .
the crude odds ratio ( or ) of the copd - ps questionnaire for ao was 5.52 , and the sensitivity of copd - ps questionnaire was 66.7% and the specificity was 73.4% . in this population - based study that included never - smokers , a cutoff point of 20 on
the crude or of the ipag questionnaire for ao , using a cutoff point of 20 , was 6.56 .
if a cutoff point of 17 was used on the ipag questionnaire , the sensitivity was higher ( 86.0% ) but both the specificity and auc were much lower , 46.2% and 0.66% , respectively .
if a cutoff point of 20 was used instead of 17 , the sensitivity was slightly lower ( 71.3% ) but both the specificity and auc were higher , 75.2% and 0.72% , respectively .
roc curves were generated to measure the properties of the copd - ps and the ipag questionnaires in discriminating subjects without ao from those with ao .
the auc values obtained from the roc curve by discriminating ao from no ao were 0.747 ( 95% confidence interval [ ci ] , 0.7070.788 ) for the copd - ps questionnaire and 0.775 ( 95% ci , 0.7350.816 ) for the ipag questionnaire ( figure 1 ) .
there was no significant difference in the auc values with the two questionnaires ( p=0.09 ) . between the copd - ps and ipag questionnaires ,
no statistically significant differences were founded in terms of sensitivity , specificity , or positive and negative predictive values .
however , compared with the copd - ps questionnaire , the ipag questionnaire had superior likelihood ratios for both a positive ( 2.51 vs 2.59 ) and negative test ( 0.45 vs 0.40 ) , with nonoverlapping cis ( table 4 ) . reclassifications of subjects with and without ao are summarized in table 5 . for 672 ( 30.7% ) subjects without ao ,
classification improved using the model with the copd - ps questionnaire , and for 549 ( 25.1% ) subjects , it became worse , with the net gain in reclassification proportion of 0.056 . for subjects with ao , classification was improved in 21 subjects ( 14.0% ) and less accurate in 28 subjects ( 18.7% ) , with the net gain in reclassification proportion of 0.047 .
thus , the categorical nri was 0.0096 ( 95% ci , 0.08680.106 ; p=0.845 ) .
the continuous nri and idi for predicting the presence of ao using the model with the copd - ps questionnaire against the ipag questionnaire were 0.107 ( 95% ci , 0.2730.058 ; p=0.203 ) and 0.014 ( 95% ci , 0.0330.006 ; p=0.182 ) , respectively , and these were not statistically significant ( table 5 ) .
the copd - ps and the ipag questionnaires had only a marginal difference in their ability to discriminate between the subjects with and without ao .
in the present population - based study , the japanese version of the copd - ps questionnaire was compared with the ipag questionnaire in a general japanese population at the age of 40 years or older .
the ipag questionnaire had superior likelihood ratios of both positive and negative tests compared with those of the copd - ps questionnaire .
however , in comparison with two questionnaires , no significant differences were founded in the auc values obtained from the roc curves discriminating between subjects with and without ao and in the sensitivity , specificity , or positive and negative predictive values .
the two questionnaires were correlated with each other , fev1/fvc , and for both of them , the ors were significantly greater than 1.0 .
these findings suggest that the copd - ps and the ipag questionnaires are useful screening tools for detecting persistent ao . in addition , the subjects with a 4 point on the copd - ps questionnaire and those with a 20 point on the ipag questionnaire are at increased risk for ao .
overall , the categorical and continuous nri and idi for predicting the presence of ao using the model with the copd - ps questionnaire were 0.0096 ( 95% ci , 0.08680.106 ; p=0.845 ) , 0.107 ( 95% ci , 0.2730.058 ; p=0.203 ) , and 0.014 ( 95% ci , 0.0330.006 ; p=0.182 ) , respectively .
reclassifications showed the ipag questionnaire to be superior to the copd - ps questionnaire ; however , there was no significant difference between the two questionnaires .
a cutoff point of 17 on the ipag questionnaire is used in general health checkup settings and general practices in japan.24 in this study , we found that a cutoff point of 20 was superior .
the reason for this discrepancy is not clear , although it may be due at least in part to the backgrounds of the study subjects .
the present study was population based and included never - smokers . in contrast , in a previous study that enrolled subjects in general health checkup settings , a cutoff point of 17 resulted in a higher sensitivity of 86.0% and a smaller auc of 0.66 ( lower than 0.70 ) than a cutoff point of 20.24 the present study was implemented in the town of hisayama , in which the age and occupational distributions of the population have been almost identical to those of japan as a whole , and thus , we recommend a cutoff point of 20 for the general japanese population .
there were only marginal differences between the two questionnaires in terms of ability to discriminate between subjects with and without ao .
moreover , the copd - ps questionnaire consists of fewer items than the ipag questionnaire and requires less time to complete .
it takes ~5 minutes to fill out copd - ps questionnaire , however , the completion of the ipag questionnaire takes ~510 minutes . in this regard ,
the japanese version of the copd - ps questionnaire should be an adequate measure for large - scale screening for possible ao .
 backgroundthe incidence of chronic obstructive pulmonary disease ( copd ) is increasing worldwide . in japan and other countries , 
 epidemiological studies have found that many patients with copd are underdiagnosed and untreated , and thus , early detection and treatment of copd has been emphasized . 
 screening questionnaires may have utility in the initial detection of copd.objectivethis study aimed to validate and compare the copd population screener ( copd - ps ) and the international primary care airway group ( ipag ) questionnaires in a general japanese population.patients and methodseligible subjects 40 years of age and older living in the town of hisayama were solicited to participate in a health checkup in 2012 . 
 all subjects 4079 years of age without physician - diagnosed asthma or lung resection were recruited , and 2,336 subjects who fully completed both questionnaires and who had valid spirometry measurements were analyzed . 
 persistent airflow obstruction ( ao ) was defined by a postbronchodilator forced expiratory volume in 1 second / forced vital capacity < 0.70 . 
 receiver operating characteristic curves , net reclassification improvement , and integrated discrimination improvement were used to examine the ability of the copd - ps and ipag questionnaires to discriminate between subjects with and without ao.resultsthe overall area under the receiver operating characteristic curve for the copd - ps questionnaire was 0.747 ( 95% confidence interval [ ci ] , 0.7070.788 ) and for the ipag was 0.775 ( 95% ci , 0.7350.816 ) , with no significant difference ( p=0.09 ) . 
 the net reclassification improvement and integrated discrimination improvement were 0.107 ( 95% ci , 0.2730.058 ; p=0.203 ) and 0.014 ( 95% ci , 0.0330.006 ; p=0.182 ) , respectively.conclusionthe five - item copd - ps questionnaire was comparable to the eight - item ipag for discriminating between subjects with and without ao . the copd - ps is a simple and useful screening questionnaire for persistent ao . 
Introduction
Methods
Study population
Study design
COPD-PS
IPAG questionnaire
Statistical analysis
Results
Participant characteristics
Discriminating subjects with and without AO
Discussion
Conclusion