BACKGROUND Induced sputum (IS) using the cytospin technique has been extensively employed to characterize inflammatory airway diseases; however, procedures of cell enrichment based on cytospin increase the analytical costs and require slide processing within a short period of time after sampling. STUDY OBJECTIVES To compare three different techniques for cytologic analysis of IS, and to determine the time required by each method and the costs involved. DESIGN Cross-sectional study. SETTING Tertiary-care university hospital. PATIENTS AND MEASUREMENTS Eighty-nine patients with asthma and 11 subjects without asthma were submitted to increasing hypertonic saline solution concentrations of 2, 3, 4, and 5% for 7 min for sputum induction. Samples were smeared without treatment with 0.1% dithiothreitol (DTT) [technique A], after treatment with DTT (technique B), and after treatment with DTT and cytospin (technique C). All slides were air-dried and stained with Leishman stain. Two independent observers counted at least 200 inflammatory cells on each slide. RESULTS Eighty percent of the slides processed by techniques A and B and 65% of the slides processed by technique C represented sputum samples of acceptable quality. The eosinophil percentages in sputum obtained by techniques A and C were closely correlated, as also were those obtained by techniques B and C (r = 0.64 and r = 0.63, respectively; p < 0.01). There was a positive correlation for eosinophils when we compared techniques A and B (r = 0.57, p < 0.01). The neutrophil correlation was significant when the three techniques were compared (technique A vs technique B, r = 0.66; technique A vs technique C, r = 0.51; and technique B vs technique C, r = 0.57; p < 0.01). Bland-Altman analysis showed a good agreement for eosinophil and neutrophil counts when techniques A and B were compared to technique C. CONCLUSIONS The three techniques are good indicators of lung inflammation. Techniques A and B are less time consuming and are of lower cost.

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@article{SaraivaRomanholo2003ComparisonOT, title={Comparison of three methods for differential cell count in induced sputum.}, author={Beatriz Mangueira Saraiva-Romanholo and Viviani Barnab{\'e} and Ana L{\'u}cia Innaco de Carvalho and Milton A Martins and Paulo Hil{\'a}rio do Nascimento Saldiva and Maria do Patroc{\'i}nio Ten{\'o}rio Nunes}, journal={Chest}, year={2003}, volume={124 3}, pages={1060-6} }