Establish New Reference Value Of Pef For Adults And Evaluate The Effect Of Detecting Al Of Subjects With Copd

Background: The diagnosis of COPD is mainly based on airflow limitation status of patients, defining post-bronchodilator FEV1/FVC<0.70 as AL by spirometry measurement. Spirometry test is not always available in primary care settings due to social economic, skills of operators and expenses reasons. Of all patients with COPD in China, only 6.5% had ever been tested by spirometry. Establishing a method for early screening of AL of patients with COPD is an urgent need, which would be suitable for community clinic of China.Peak expiratory flow (PEF) is a measure of maximal expiratory flow that is used to assess qualitative and quantitative effort in spirometry maneuvers and is clinically utilized independently for asthma monitoring. Measurement of the PEF requires only a short maximal expiration of patient, and much less skills required for technician to achieve reliable data than for spirometry test. This study would evaluate the effects of PEF as a primary tool for detecting AL of patients with COPD.Objective:Establish new reference value of PEF for adults in South China, and evaluate the effect of PEF on detecting AL of subjects with COPD. PartⅠ: Establishment new reference value of PEF for adults aged≥40 years in SouthChinaMethods: 1,Normal subjects aged≥40 years, who had never smoked, without history of respiratory and other serious illness (bronchial asthma, pneumonia, chronic obstructive pulmonary disease, tuberculosis, heart, liver, brain, kidney, etc.), and respiratory symptoms (coughing, phlegm, wheezing, etc.), without history of occupational exposure to harmful materials and biomass smoke in the recent ten years and with a normal spirometry, were recruited from Guangdong province of China. 2,Measurement of PEF was carried out with a mini-Wright peak flow meter (Micropeak, UK). The highest of the three readings was taken as the final PEF of each subject. Standing height (cm) was measured without shoes. Age, sex, height, weight were recorded. 3,Linear regression equations for the spirometric parameters on age, height, and weight were computed, taken alone and then together by applying stepwise multivariant analysis. The analysis was repeated on logarithmic and square transformation of different variables to choose models with the best fit.Results: The PEF values of normal population without COPD were got. Total 553 normal subjects aged≥40 year old were recruited. It was noted that, in the all age brackets for female, as well as in the 40-49 and 50-59 age brackets for males, the values obtained in the our study presented no significant difference compared with the values suggested in the 1985 study. While there was a significant difference between the present values of 60-69 and 70-85 age brackets for males and that of in the 1985 study. When comparing with the values suggested in the Nunn, s study, a significant difference was observed for all age brackets and both genders.A new regression equations were calculated for predicting values of PEF of normal subjects older than 40 yrs in south China from height (H cm) and age (A years) as below: Male: PEF (L/min) = -83.493+1.472×Age-0.027×Age2+3.864×Height Female: PEF (L/min) = 155.036+0.79×Age-0.030×Age2+1.576×HeightPartⅡ: Evaluate the effect of detecting AL of subjects with COPDMethods: Subjects aged≥40 years were selected from Guitou county of Shaoguan and Liwan district of Guangzhou. Questionnaire and measurement of PEF was completed. Lung function was measured before and after administration of 400μg of salbutamol ( Ventolin; GlaxoSmithKline, Middlesex, UK) using the EasyOne Diagnostic Spirometery. The performance of PEF as a diagnostic test was evaluated to identify post-BD defined AL. Results: Of 4,081 subjects sampled,3,379 completed acceptable spirometry (grades A, B, or C),questionnaires and measurement of PEF. There were 345 subjects with AL, including 142 subjects with asymptomatic AL. Using questionnaire correctly identified 58.8% of those individuals with post-BD confirmed AL. A PEF screening cut-off point of 80% predicted (80%P) correctly identified 76.8% (sensitivity =76.8%, specificity =83.8%) of those individuals with post-BD confirmed AL. While a PEF screening cut-off point of 60% predicted correctly identified 100% (sensitivity =100%, specificity =96.0%) of those severe to very severe AL.Conclusions: There was a significant difference between the present values of 60-69 and 70-85 age brackets for males and that for Chinese made before. We established a new reference value of PEF for adults in South China. Using the new reference value, PEF is good at detecting patients with AL in the community. The worth of PEF for evaluating airflow limitation in the whole population was significantly much better than symptoms alone. It may be an effective method of AL screening in primary health unit of China.