Language barriers, instruction comprehension, and spirometry failure in a multilingual outpatient population: a cross-sectional study

Spirometry quality depends on patients’ ability to understand and execute standardized instructions; however, the effects of language discordance and instruction comprehension difficulties on test performance remain insufficiently studied. This study examined whether native language, instruction comprehension difficulty, and health-related document reading difficulty were associated with failed or partially successful spirometry outcomes in a multilingual outpatient population. This single-center cross-sectional study included consecutive adults referred for spirometry at Mardin Training and Research Hospital between 15 and 29 June 2026. Data were recorded contemporaneously during routine testing. Outcomes were classified as successful, partially successful, or failed; partially successful and failed tests were combined for the primary analysis because neither category met the predefined criteria for a diagnostically adequate test. Explanatory variables included native language, educational level, instruction comprehension difficulty, health-related document reading difficulty, language barrier-related instruction non-compliance, and dyspnea severity. Independent associations were assessed using multivariable logistic regression, with additional sensitivity analyses for alternative outcome definitions. Among 736 patients, 642 (87.2%) had a non-Turkish native language. Overall, 422 (57.3%) achieved a successful result, whereas 314 (42.7%) had a failed or partially successful test. Success was more frequent among Turkish native speakers than among patients with a non-Turkish native language (71.3% vs. 55.3%; OR 2.01, p = 0.005). Language barrier-related instruction non-compliance was also more common in the non-Turkish group (22.9% vs. 5.3%; OR 5.29, 95% CI 2.11–13.26; p < 0.001). Each one-level increase in instruction comprehension difficulty was associated with higher odds of a failed or partially successful outcome (aOR 1.65, 95% CI 1.34–2.03; p < 0.001). Health-related document reading difficulty (aOR 1.26, 95% CI 1.05–1.52; p = 0.015) and severe dyspnea (aOR 3.97, 95% CI 2.30–6.88; p < 0.001) were also independently associated with the combined outcome, whereas non-Turkish native language was not (aOR 0.96, 95% CI 0.56–1.64; p = 0.874). The principal associations remained in sensitivity analyses using a stricter repeatability-based success definition. Spirometry outcomes were more closely associated with difficulty understanding and executing instructions than with native language alone. The findings support further prospective evaluation of language-concordant coaching, visual support, and structured pre-test orientation in multilingual respiratory clinics.