Reference Equations Research Articles

Association between Spirometric Parameters and Depressive Symptoms in New Mexico Uranium Workers

Uranium workers are at risk of developing lung disease, characterized by low forced expiratory volume in one second (FEV1) and/or forced vital capacity (FVC). Previous studies have found an association between decreased lung function and depressive symptoms in patients with pulmonary pathologies, but this association has not been well examined in occupational cohorts, especially uranium workers. This cross-sectional study evaluated the association between spirometric measures and depressive symptoms in a sample of elderly former uranium workers screened by the New Mexico Radiation Exposure Screening & Education Program (NM-RESEP). Race- and ethnicity-specific reference equations were used to determine predicted spirometric indices (predictor variable). At least one depressive symptom [depressed mood and/or anhedonia, as determined by a modified Patient Health Questionnaire-2 (PHQ-2)], was the outcome variables. Chi-square tests and multivariable logistic regression models were used for statistical analyses. At least one depressive symptom was self-reported by 7.6% of uranium workers. Depressed mood was reported over twice as much as anhedonia (7.2% versus 3.3%). Abnormal FVC was associated with at least one depressive symptom after adjustment for covariates. There was no significant interaction between race/ethnicity and spirometric indices on depressive symptoms. Although depressive symptoms are uncommonly reported in uranium workers, they are an important comorbidity due to their overall clinical impact. Abnormal FVC was associated with depressive symptoms. Race/ethnicity was not found to be an effect modifier for the association between abnormal FVC and depressive symptoms. To better understand the mechanism underlying this association and determine if a causal relationship exists between spirometric indices and depressive symptoms in occupational populations at risk for developing lung disease, larger longitudinal studies are required. We recommend screening for depressive symptoms for current and former uranium workers as part of routine health surveillance of this occupational cohort. Such screening may help overcome workers' reluctance to self-report and seek treatment for depression and may avoid negative consequences to health and safety from missed diagnoses.

The applicability of the global lung initiative equations and other regional equations on a sample of healthy Middle Eastern adolescents.

The Global Lung Initiative 2012 (GLI-2012) spirometry equations are multi-ethnic equations that cover all ages between 3 and 95. However, there is a need to evaluate the suitability of these equations to a sample of Middle Eastern adolescents prior to being applied in clinical practice. The aim of this study is to evaluate the suitability of GLI-2012 equations and two regional equations to a sample of Jordanian adolescents. Spirometric measures were collected from 1036 healthy 14 to 17-year-old Jordanian children. z-scores, predicted values, percent predicted values, and frequency of measures below lower limit of normal (LLN) were calculated for each adolescent using the studied equations. The means of z-scores produced by GLI-2012 equations for Caucasians in forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), FEV1/FVC% and mid forced expiratory flow (FEF25-75) for boys were 0.12, -0.06, 0.34 and 0.09, respectively, while for girls they were -0.09, -0.16, 0.19 and -0.05, respectively. The mean of z-scores produced by GLI-2012 Other or Mixed equations in FEV1, FVC, FEV1/FVC% and FEF25-75 for boys were 0.74, 072, 021 and 0.33, respectively, and for girls were 0.53, 0.56,0.02 and 0.2, respectively. The frequency of measures below LLN as produced by GLI 2012 for Caucasians were significantly different from the expected 5% in FEV1 and FEF25-75 in boys only, whereas Other or Mixed produced frequencies significantly different from the expected 5% in most of the parameters. Spirometry reference equations formulated for Jordanian adolescents may improve the diagnosis and treatment of asthma in Jordan.

Peak In- and Expiratory Flow Revisited: Reliability and Reference Values in Adults

Background: While peak in- and expiratory flow rates offer valuable information for diagnosis and monitoring in respiratory disease, these indices are usually considered too variable to be routinely used for quantification in clinical practice. Objectives: The aim of the study was to obtain reproducible measurements of maximal inspiratory flow rates and to construct reference equations for peak in- and expiratory flows (PIF and PEF). Method: With coaching for maximal effort, 187 healthy Caucasian subjects (20–80 years) performed at least 3 combined forced inspiratory and expiratory manoeuvres, until at least 2 peak inspiratory flow measurements were within 10% of each other. The effect on PIF preceded by a slow expiration instead of a forced expiration and PIF repeatability over 3 different days was also investigated in subgroups. Reference values and limits of normal for PIF, mid-inspiratory flow, and PEF were obtained according to the Lambda-Mu-Sigma statistical method. Results: A valid PIF could be obtained within 3.3 ± 0.6(SD) attempts, resulting in an overall within-test PIF variability of 4.6 ± 3.2(SD)%. A slow instead of a forced expiration prior to forced inspiration resulted in a significant (p < 0.001) but small PIF increase (2.5% on average). Intraclass correlation coefficient for between-day PIF was 0.981 (95% CI: 0.960–0.992). Over the entire age range, inter-subject PIF variability was smaller than in previous reports, and PIF could be predicted based on its determinants gender, age, and height (r² = 0.53). Conclusions: When adhering to similar criteria for the measurement of effort-dependent portions of inspiratory and expiratory flow-volume curves, performed according to current ATS/ERS standards, it is possible to obtain reproducible PIF and PEF values for use in routine clinical practice.

Predictors and reference equations for augmentation index, an arterial stiffness marker, in healthy children and adolescents

OBJECTIVES:To investigate predictors and propose reference equations for the augmentation index normalized to 75 bpm heart rate (AIx@75) in healthy children and adolescents.METHODS:This was a cross-sectional, observational study involving 134 healthy children and adolescents aged 9 to 19 years old. Participants were categorized into child (n=53) and adolescent (n=81) groups, as well as into male (n=69) and female (n=65) groups. We evaluated AIx@75, vascular and hemodynamic parameters, anthropometric data, physical activity profile, and quality of life (Peds-QL4.0; physical, emotional, social and school domains).RESULTS:The predictors of AIx@75 in the whole sample were age, peripheral diastolic blood pressure (pDBP), mean arterial pressure, pulse pressure amplification (PPA), systolic volume (SV), cardiac index (CI), and pulse wave velocity (PWV; R2=80.47%). In the male group, the predictors of AIx@75 were SV, CI, total vascular resistence (TVR), and PWV (R2=78.56%), while in the female group, they were pDBP, PPA, SV, and PWV (R2=82.45%). In the children, they were pDBP, PPA, SV, and PWV (R2=79.17%), while in the adolescents, they were body mass index, pDBP, PPA, SV, TVR, and PWV (R2=81.57%).CONCLUSION:In the present study, we used a representative sample from Belo Horizonte to establish normality values of AIx@75. We also identified, for the first time, independent predictors of AIx@75 in healthy children and adolescents categorized by sex and age. Determining AIx@75 reference equations may facilitate the early diagnosis of preclinical atherosclerosis and allow an objective measure of the vascular effects of therapeutic interventions aimed at modifying cardiovascular risk factors.

A NEW APPROACH TO MEDICAL DIAGNOSIS OF COVID-19 AND CONTROLLING THE EFFECTS OF COVID-19 ON ARTERIAL BLOOD GAS WORKING

Aim: The purpose of this study is to provide information about the effect of the defense mechanism formed by the lung mucosal surface against Covid-19 and the effect of Covid-19's lung involvement on Arterial Blood Gas Values, whose number of cases and mortality rate increases day by day in our country. In addition, by sharing a new method in the diagnosis of Covid-19, important issues in the monitoring of Covid-19 patients with a high symptom burden and high risk of complications associated with lung damage were highlighted. Method: The blood values of 4000 patients who read the consent form and gave consent were collected in the SPSS 26 program in our study conducted in various public hospitals within the city of Istanbul with the permission of Istanbul Provincial Health Directorate with the number 15916306-604.02 and dated 08.09.2020. With our quantitative research, it is possible to interpret the arterial blood gas values of patients who have been diagnosed with covid-19 positive, to determine the common output and to determine the treatment methods, drugs, etc. It is aimed to be a resource for the studies. Common values were searched in the formed control groups and analyzed in accordance with the Henderson-Hasselbalch equation and in accordance with the literature. Arterial and vein blood from the patients participating in the study were collected in anaerobic environment with sterile syringes containing 1.0 or 5.0 mL lyophilized heparin. During blood collection, necessary measures have been taken to prevent or minimize blood contact with air. Since arterial blood gas collection requires expertise, no results that could be interpreted as suspicious were included in the study. Analyzes were performed with pH, pO2, pCO2, HCO3, LDH and Hgb values of 4000 participants. Results: Our study includes 4000 people between the ages of 19-88, who have been diagnosed with Covid-19 and voluntarily agree to participate in our study. 58% of the patients who participated in the study by approving the consent form were male and 42% were female. In order for the blood values of the deceased patients to be used in our study, permission was also requested from their relatives. In this group, 68% of the participants are male and 32% are female participants. It was found that the pO2 and pCO2 ratio of 4000 patients participating in the study did not exceed 10% of the LDH and HCO3 ratio (1O X (LDH) / 100 X (HCO3)&gt; pO2 / pCO2). If the equation is correct in the equation [(LDH) X (pCO2)] / [(HCO3) X (pO2)] ≤ (Hgb), the covid-19 diagnostic status is positive. Conclusion: : It has been determined that the pO2 / pCO2 ratio does not exceed 10% of the LDH / HCO3 ratio in the critical cases examined within the scope of the research. As this rate decreased, the rate of survival of patients also decreased. Therefore, in positive cases, a reference equation that can detect covid-19 positivity has been found by looking at whether there is an anion gap and metabolic acidosis is observed and LDH level. This formula; [(LDH) X (pCO2)] / [(HCO3) X (pO2)] ≤ (Hgb). When the formula was applied, it was determined that the ratio of [(LDH) X (pCO2)] / [(HCO3) X (pO2)] was equal or less than the value of hemoglobin (Hgb).

Control of ground objects escorting from aircraft

The synthesis problem of adjuster for software automatic escorting of a ground mobile object using a surveysearch system of an aircraft is considered. The calculation of the control function is carried out by the method of the inverse dynamic problem separately for two angular channels. It is proposed to take into account the restrictions on the magnitude of the control action and on the angles of the line of sight, as well as to use the nonlinear Lewis equation with a correcting differential term as a reference equation. Keywords software support; synthesis of program control; method of the inverse dynamic problem

Spirometry Abnormalities and Its Associated Factors Among Primary School Children in a Nigerian City.

Background:There is paucity of data on objectively measured lung function abnormalities in Nigerian children using diagnostic testing methods such as spirometry. Such assessments could prompt early diagnosis and therapeutic interventions.Methods:This was a cross sectional study among children aged 6 to 12 years in South-Eastern Nigeria. We selected participants from one school using a multistage stratified random sampling technique. A structured respiratory questionnaire was administered to obtain necessary data. The lung functions of the children were measured by spirometry. We used Lower Limits of Normal (LLN) based on GLI reference equations for African-American and mixed ethnicities to define abnormal spirometry. We studied the association between the exposures and lung function using logistic regression/chi-squared tests.Results:A total of 145 children performed acceptable and repeatable tests. There were 73 males (50.3%), mean age of 9.13 years (+1.5) and age range 6 to 12 years. Frequency of respiratory symptoms was cough- 64 (44.1%) and wheeze in 19 (13.1%). Using GLI for African-Americans, fifty-five (37.9%) children had abnormal spirometryobstructive pattern in 40 (27.6%) and restrictive pattern in 15 (10.3%). The two references showed significant differences in interpretation of abnormality (χ2 = 72.86; P < .001). Respiratory symptom-wheeze was an independent determinant of abnormal lung function in this population.(OR = 0.31; 95%CI: 0.10–0.94; P = .04)Conclusion:There is a high burden of respiratory symptoms and abnormal spirometry among these children. The need for objective evaluation of lung function especially for children with respiratory symptoms is evident.

Reference values and regression equations for predicting the 6-minute walk distance in Saudi adults aged 50-80 years: A cross- sectional study.

The 6-minute walk test (6-MWT) is commonly used to measure functional capacity in clinical and research settings. The reference equations for predicting the 6-minute walk distance (6-MWD) in different populations have been established; however, there is a lack of information regarding healthy Saudi individuals over 50 years old. This study aimed to establish the reference values of 6-MWD in a sample of healthy Saudi adults aged 50-80years, develop regression equations for the established 6-MWD, and compare the measured 6-MWD in the present study with the predicted 6-MWD derived from the previously published regression equations. In total, 210 healthy Saudi volunteers aged 50-80 years participated in this cross-sectional study. The 6-MWT was performed according to the American Thoracic Society (ATS) guidelines. Lung function, physical activity, blood pressure, heart rate, oxygen saturation, exertion level of leg fatigue, and sensation of dyspnea were measured. The mean 6-MWD was 396.2 ± 69.4 m. It was significantly correlated with age, sex, height, body mass index (BMI), and physical activity. The predictors of 6-MWD were age and BMI for men, while they were age, BMI, and height for women. They accounted for 25% and 35% of the total variance of 6-MWD for men and women, respectively. The measured 6-MWD was significantly shorter than the predicted 6-MWD. Saudi populations have significantly shorter 6-MWDs than those reported in other ethnic groups. The sex-specific equations developed in this study are expected to provide a useful measure of 6-MWT for Saudi adults. However, further investigation is required to validate the application of these equations to individuals living in different regions of Saudi Arabia.

Reference values for the Modified Timed Up and Go Test in Saudi children aged 4–12 years old in Riyadh city: cross-sectional study

Purpose The study aimed to report within-session reliability, estimate the reference values for the Modified Timed Up and Go (mTUG) test in typically developing (TD) Saudi children aged 4–12 years old, develop a reference equation for the estimated mTUG, and compare the measured mTUG in the present study with the predicted mTUG obtained from the previous regression equation. Methods In this cross-sectional observational study, anthropometric measurements and mTUG test were investigated in 805 child. The association between the mTUG test and predictive variables was studied. Results Average mTUG speed was 4.63 ± 0.68 s. Within-session reliability was excellent with intraclass correlation coefficient of 0.90. The test was significantly and negatively correlated with age, height, and weight (r = −0.66, p = .00), (r = −0.54, p = .01), and (r = −0.33, p = .01) respectively. According to the stepwise regression analysis, age and weight were the predictors and explained 47% of total variance of mTUG scores. Conclusion This study provided the mTUG reference values that can be used clinically to evaluate functional mobility and dynamic balance in TD Saudi children aged 4–12 years. The mTUG scores can be predicted as a function of age and weight. KEY MESSAGES Modified Timed Up and Go test used to assess the functional mobility and dynamic balance for children with or without developmental abnormalities. Availability of reference values according to age is helpful to compare the performance of children at same ages.

Guidance to the applicability of the Global Lung Initiative spirometry reference equations for South African populations

Guidance to the applicability of the Global Lung Initiative spirometry reference equations for South African populations

Guidance to the applicability of the Global Lung Initiative spirometry reference equations for South African populations

Guidance to the applicability of the Global Lung Initiative spirometry reference equations for South African populations

Predicting the handgrip strength across the age span: Cross-validating reference equations from the 2011 NIH toolbox norming study

Study DesignThis is a cross-sectional observational study. BackgroundReference equations for describing hand-grip strength across the age span were derived from the 2011 NIH Toolbox norming study. PurposeThe purpose of this study was to cross-validate reference equations by evaluating its predicting power on a separate, independent data set from the 2011-2014 National Health and Nutrition Examination Survey (NHANES) study MethodsObserved hand-grip strength data from 13,676 noninstitutionalized participants were obtained from the NHANES study. Best values (best from 3 trials) and the mean values (averaged from 3 trials) were determined for each hand. Using the age (yr), height (m), and weight (kg), we computed predicted grip strength values for dominant and nondominant hands using the reference equations. For validation, three predictability measures: the correlation coefficient, residuals, and accuracy, were used along with the Bland-Altman plot. ResultsThe predicted values highly correlated with observed values (r = 0.90, ICC = 0.89). In predicting best values, means (SD) of residuals were 1.41 (5.57) and 1.03 (5.44) kg for dominant and nondominant hands, respectively. In predicting mean values, means (SD) of residuals were −0.23 (5.42) and −0.54 (5.31) kg for dominant and nondominant hands, respectively. Root mean square error ranged from 4.10 (female's nondominant mean values) to 6.74 (male's dominant best values). About 5.56% fell outside of the 95% confidence interval of the prediction. ConclusionsWe acknowledged that the two studies' hand-grip protocols (NIH Toolbox, NHANES) were different. Results provided the preliminary predicting performance of the reference equations derived from the NIH Toolbox study.

Predicted Reference Equations for Spirometry Indices as a Proxy from Anthropometry Measurements of Nigerian Children with Sickle Cell Anaemia Aged 5-12 Years.

Significant morbidity and mortality in patients with sickle cell disease are accounted for by lung complications. To facilitate good respiratory care for children with sickle cell anaemia the generation of local predicted values is highly important. To determine the reference equations for spirometry indices estimation in children with sickle cell anaemia, which can be readily used as proxy when there is no easy accessibility to spirometer. A cross-sectional study with linear regression models developed to estimate reference values for spirometric indices in Nigerian children with sickle cell anaemia aged 5-12 years. Age as independent variables for estimation of forced expiratory volume in 1 s (FEV1) was associated with lowest coefficient of determination (R2) and highest standard error. The coefficient of determination (R2) and standard error was highest and lowest, respectively, when arm span was used to determine peak expiratory flow rate (PEFR). Prediction models for PEFR and FEV1 gave the closest mean estimates that were 0.18 and 0.16 lower and higher than the actual mean PEFR and FEV1, respectively, but the differences was significant only in FEV1. On the contrary the prediction models for forced vital capacity (FVC) gave mean estimates that was 1.02 higher than the actual mean FVC, however, the finding was not significant. Preferred proxy for spirometry indices in children with sickle cell anaemia may be arm span.

Enhanced scaling effects significantly lower the ability of MODIS normalized difference snow index to estimate fractional and binary snow cover on the Tibetan Plateau

MODIS fractional (FSC) and binary (BSC) snow-cover data are important for obtaining accurate spatiotemporal snow-cover information for the Tibetan Plateau (TP) where rapid warming is closely related to snow-cover changes. However, FSC and BSC data are no longer provided in the newly released version (v6) of the MODIS snow cover product, having been replaced with normalized difference snow index (NDSI) data. Recent studies have observed clearly lower accuracy of MODIS snow cover data on the TP than in other areas, possibly implying that there are strong scaling effects due to the complex terrain and land cover which are not well understood. A total of 353 Landsat-8 scenes covering most parts of the TP are used to establish a new empirical relationship between FSC and MODIS NDSI for FSC estimation and a new NDSI threshold for BSC estimation. The results indicate that the new regression model (mean root-mean-squared-deviation (RMSD): 0.22) has a better FSC estimation accuracy than the previously used global reference equation (mean RMSD: 0.24) and that the new NDSI threshold of 0.29 (mean Cohen’s Kappa (CK): 0.49) outperforms the global reference NDSI threshold of 0.4 (mean CK: 0.40) in BSC estimation. The relatively low accuracy could be due to an enhanced scaling effect. The 30-m Landsat-8 NDSI data are upscaled to 500-m (MODIS) to analyze the scaling effects on FSC and BSC estimates made using MODIS NDSI. We find that the methods using MODIS NDSI have much lower estimation accuracy, for both FSC and BSC, compared with those using upscaled Landsat-8 NDSI. An analysis of variance (ANOVA) test which considers 512 combinations of aspect, slope and normalized difference vegetation index (NDVI) further demonstrates that the enhanced scaling effects are mainly caused by terrain factors (i.e. aspect and slope). The optimal NDSI threshold for estimating BSC generally increases with slope and decreases as the aspect varies from the southeast to northwest. This study has important implications for the optimal use of MODIS NDSI snow cover data on the TP and highlights the importance of developing more advanced methods which take more factors into account.

Normative Cardiopulmonary Exercise Test Responses at the Ventilatory Threshold in Canadian Adults 40 to 80 Years of Age

Physiologic and symptom responses at the ventilatory threshold (Tvent) during incremental cardiopulmonary exercise testing (CPET) can provide important prognostic information. This study aimed to develop an updated normative reference set for physiologic and symptom responses at Tvent during cycle CPET (primary aim) and to evaluate previously recommended reference equations from a 1985 study for predicting Tvent responses (secondary aim). Participants were adults 40 to 80 years of age who were free of clinically relevant disease from the Canadian Cohort Obstructive Lung Disease. Rate of oxygen consumption (V˙O2) at Tvent was identified by two independent raters; physiologic and symptom responses corresponding to V˙O2 at Tvent were identified by linear interpolation. Reference ranges (5th-95th percentiles) for responses at Tvent were calculated according to participant sex and age for 29 and eight variables, respectively. Prediction models were developed for nine variables (oxygen pulse, V˙O2, rate of CO2 production, minute ventilation, tidal volume, inspiratory capacity, end-inspiratory lung volume [in liters and as percentage of total lung capacity], and end-expiratory lung volume) using quantile regression, estimating the 5th (lower limit of normal), 50th (normal), and 95th (upper limit of normal) percentiles based on readily available participant characteristics. The two one-sided test of equivalence for paired samples evaluated the measured and 1985-predicted V˙O2 at Tvent for equivalence. Reference ranges and equations were developed based on 96 participants (49%men) with a mean ± SD age of 63 ± 9 years. Mean V˙O2 at Tvent was 50%of measured V˙O2 peak; the normal range was 33%to 66%. The 1985 reference equations overpredicted V˙O2 at Tvent: mean difference in men, -0.17 L/min (95%CI, -0.25 to -0.09 L/min); mean difference in women, -0.19 L/min (95%CI, -0.27 to -0.12 L/min). A contemporary reference set of CPET responses at Tvent from Canadian adults 40 to 80 years of age is presented that differs from the previously recommended and often used reference set from1985. ClinicalTrials.gov; No.: NCT00920348; URL: www.clinicaltrials.gov.

Newly developed multiple-breath washout reference equations from the CHILD Cohort Study: implications of poorly fitting equations.

Using inappropriate reference equations would provide incorrect estimate of z-scores, which would cause misdiagnosis. Appropriate representative normative reference data must be available to correctly interpret individual lung function results. https://bit.ly/3dcNZ5p

Reference equations for parameters of impulse oscillometry in Egyptian children and adolescents

BackgroundImpulse oscillometry (IOS) is important in diagnosing respiratory functions in non-cooperative children. Studies are rising nowadays to establish reliable reference values of IOS for children of different ethnicities. No available data about the regression equations for parameters of IOS for Egyptian children and adolescents. So, our study aimed to develop regression equations for parameters of IOS in Egyptian children and adolescents in relation to their age, weight, height, and body mass index.ResultsHeight and age affected the regression equation of impedance at 5 Hz (Z5 Hz) and resistance at 5 Hz (R5 Hz) in both males and females, resistance at 20 Hz (R20 Hz) in males and reactance at 5 Hz (X5 Hz) in females. Height affected the regression equation of R20 Hz in females, resonant frequency (Fres) in males, and the area of reactance (AX) in both males and females. While age affected the equation of X5 Hz in males and Fres in males.ConclusionsHeight and age were the most predictive values affecting the regression equation of IOS in Egyptian children and adolescents.

Predicting the Handgrip Strength across the Age Span: Validating Reference Equations from the 2011 NIH Toolbox Norming Study

Predicting the Handgrip Strength across the Age Span: Validating Reference Equations from the 2011 NIH Toolbox Norming Study

The impact of changing to the Global Lung Function Initiative reference equations for transfer factor in paediatrics.

The Global Lung Function Initiative (GLI) all-age reference equations for carbon monoxide transfer factor were published in 2017 and endorsed by the European Respiratory Society and American Thoracic Society. In order to understand the impact of these new reference equations on the interpretation of results in children referred from haematology and oncology paediatric services, we retrospectively analysed transfer factor results from any paediatric patient referred from haematology/oncology in the period 2010–2018. We examined transfer factor of the lung for carbon monoxide (TLCO), transfer coefficient of the lung for carbon monoxide (KCO) and alveolar volume (VA) from 241 children (age range 7–18 years, 130 male). The predicted values from Rosenthal and GLI were plotted against height. The difference in interpretation of results was analysed by looking at the percentage of patients below the lower limit of normal for each parameter. Overall, the Rosenthal predicted values for TLCO were higher than those predicted by GLI. Predicted KCO using Rosenthal was higher in all observations. In contrast, the Rosenthal predicted VA was generally lower than the GLI value. The GLI predicted values for transfer factor show considerable differences compared with currently used paediatric UK reference values, differences that will have a significant impact on interpretation of results.

Predicted values for the forced expiratory flow adjusted for forced vital capacity, a descriptive study

BackgroundThe forced expiratory flows (FEFs) towards the end of the expiration may be more sensitive in detecting peripheral airways obstruction compared to the forced expiratory volume in 1 s and forced vital capacity (FVC). However, they are highly variable. A partial solution is to adjust the FEFs for FVC (FEF/FVC). Here we provide reference equations for these adjusted FEFs at 25%, 50%, 75% and 25–75% of FVC, which are currently lacking.MethodsWe included pulmonary healthy, never-smoker adults; 14 472 subjects from Lifelines, a biobank for health research, and 338 subjects from the department's control cohorts (NORM and Fiddle). Reference equations were obtained by linear regression on 80% of the Lifelines dataset and validated on the remaining data. The best model was defined as the one with the highest adjusted R2-value. The difference in variability between adjusted and unadjusted FEFs was evaluated using the coefficient of variation.ResultsFor all adjusted FEFs, the best model contained age, height and weight. The adjustment improved the coefficient of variation of the FEF75 from 39% to 36% and from 43% to 40%, respectively, in males and females. The highest percentage of explained variance by the reference equation was obtained for FEF75/FVC, 32%–38% for males, and 41%–46% for females, depending on the validation set.ConclusionWe developed reference equations for FVC-adjusted FEF values. We demonstrated minimally yet significantly improved variability. Future studies in obstructive airway diseases should demonstrate whether it is worthwhile to use these (predicted) adjusted FEF values.