Bland-Altman plots of the inter-observer agreement for differential sputum cell counts. Sputum neutrophil, eosinophil, and macrophage cell counts are represented in plots (a), (b), and (c), respectively. The dashed lines represent the inter-observer bias (± 1.96 SD). For the neutrophil and macrophage analyses, the ratio of the measurements was plotted, avoiding the need for log transformation of the data. The eosinophil analysis plotted the difference of the measurements. Definition of abbreviations: A = first cytotechnologist cell count; B = second cytotechnologist cell count.