Computational protocol: Contrasting diagnosis performance of forced oscillation and spirometry in patients with rheumatoid arthritis and respiratory symptoms

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Protocol publication

[…] The impedance curves (resistance and reactance) were studied over the frequency range from 4 to 32 Hz. The analysis of linear regression in the resistive component of the impedance in the frequency range between 4 and 16 Hz was used to determine the intercept resistance (R0). The intercept is related to the total resistance of the respiratory system and is usually used as an index of airway obstruction (). The mean resistance (Rm), which is related to the airway caliber (), was also calculated for the frequency range from 4 to 16 Hz. The slope of the resistive component of the respiratory impedance (S) was also obtained and is associated with respiratory system homogeneity (,). The resonance frequency (fr) is defined as the frequency at which the rectance equals zero and is associated with the homogeneity of the respiratory system (). The dynamic compliance of the respiratory system (Crs,dyn), which includes the airways, lung and chest wall, was estimated using the reactance (Xrs) at 4 Hz with the equation Crs,dyn = -1/(2πfXrs). The impedance module at 4 Hz (Zrs4) was also estimated. Physiologically, this parameter represents the total mechanical load of the respiratory system ().The sample size for this study was calculated using MedCalc version 8.2 (Medicalc Software, Mariakerke, Belgium). It was based on an anticipated comparison of the mean values of R0 obtained in preliminary studies () and an assumption of Type I and Type II errors of 1%. The minimal sample size required was 18 subjects in each group.The commercial softwares MicrocalTM Origin® 6.0 (Microcal Software Inc., Northampton, USA) and STATISTICA for Windows, release 5.0 (StatSoft Inc., Tulsa, USA), were used to compare the differences between the groups. Because of the number of subjects of each group, a non-parametric Mann-Whitney U test was applied. A p-value of less than 0.05 was considered statistically significant.The clinical potential of the FOT indexes in the early detection of respiratory alterations in RA was evaluated by means of receiver operating characteristic (ROC) analyses, which were conducted using MedCalc 8.2 (Medicalc Software, Mariakerke, Belgium).Comparisons of the AUC among parameters obtained from the FOT and spirometry were conducted using MedCalc 8.2 following the theory described by Metz (). The sensitivity, specificity, and AUC of spirometry and the FOT were obtained based on the optimal cut-off point, as determined from the ROC curve analysis (). […]

Pipeline specifications

Software tools MedCalc, Statistica
Application Miscellaneous
Organisms Homo sapiens
Diseases Arthritis, Rheumatoid, Lung Diseases, Respiratory Insufficiency, Sleep Apnea Syndromes, Respiratory System Abnormalities