Comparison of three methods for differential cell count in induced sputum.
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.


OBJECTIVE
To compare three different techniques for cytologic analysis of IS, and to determine the time required by each method and the costs involved.


METHODS
Cross-sectional study.


METHODS
Tertiary-care university hospital.


METHODS
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.
Saraiva-Romanholo
Beatriz M
BM
Department of Medicine, School of Medicine, University of São Paulo, São Paulo, Brazil.
Barnabé
Viviani
V
Carvalho
Ana Lúcia I
AL
Martins
Milton A
MA
Saldiva
Paulo H N
PH
Nunes
Maria do Patrocínio T
Mdo P
D000293:Adolescent; D000328:Adult; D000368:Aged; D001249:Asthma / Q000175:diagnosis / Q000276:immunology*; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007958:Leukocyte Count / Q000379:methods*; D018655:Lymphocyte Count / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate / Q000502:physiology; D012016:Reference Values; D012680:Sensitivity and Specificity; D013183:Sputum / Q000166:cytology* / Q000276:immunology