Perceived stress as a determinant of spirometry performance: Development and application of a cooperation index

Background Spirometry quality relies heavily on patient cooperation, yet the psychological determinants of poor performance remain understudied. This study aimed to explore the relationship between perceived stress and spirometry quality by developing and applying a novel Cooperation Index (CI). Methods A cross-sectional study was conducted among 237 adults undergoing spirometry. Cooperation was quantified using a CI (range 0-9), based on eight ATS/ERS-derived quality criteria. Perceived stress was assessed using the 10-item Perceived Stress Scale (PSS); scores ≥ 27 were considered high. Sociodemographic, clinical, and psychological data were collected, and multivariable logistic regression identified factors independently associated with limited cooperation (CI ≤ 4). Results Only 60.8% of patients achieved optimal cooperation. Limited cooperation was significantly more frequent in patients with high perceived stress (OR = 5.34; 95% CI: 1.87-15.23; p = 0.002) and those aged ≥ 65 years (OR = 3.65; 95% CI: 1.44-9.23; p = 0.006). High stress was associated with delayed expiratory start, insufficient duration, and submaximal effort. Other factors, including BMI, dyspnea, smoking, and insomnia, were not independently linked to cooperation. Conclusion Perceived stress was independently associated with limited cooperation during spirometry. The proposed CI offers a reproducible tool to assess and stratify patient cooperation. Incorporating stress assessment into pulmonary function testing could enhance test reliability and guide supportive interventions.