Since emphysema was reported at both PLCO baseline and PLCO follow-up, we explored the concordance of these reports. Almost half (n = 333) of the total 882 emphysema cases were reported at baseline. Concordance between reports of emphysema at baseline and follow-up questionnaires was high; among the 882 emphysema cases in our analyses, 26% (n = 229) reported emphysema on both baseline and follow-up questionnaires, and 62% (n = 545) reported emphysema at follow-up but not at baseline. Discordant responses were recorded for 9% (n = 80) of cases; these participants reported emphysema on the first encounter but not the second. Three percent of emphysema cases were missing emphysema data on one questionnaire (n = 4 missing baseline emphysema data, n = 24 missing follow-up emphysema data). In logistic regression models, we observed similar associations between TTFC and emphysema reported at baseline and at follow-up. Compared to TTFC >60 minutes, the multivariate adjusted ORs (95% CI) for emphysema at the baseline questionnaire were 1.49 (0.95–2.36), 1.50 (0.98–2.31), and 2.19 (1.36–3.54) for TTFC 31–60 minutes, 6–30 minutes, and ≤5 minutes, respectively;
