Alcohol fixation of induced sputum samples for applications in rural communities.
BACKGROUND
Sputum induction is a tool recommended for the assessment of airway inflammation and disease management. Currently, its use is limited because samples need to be processed within 3 h of induction (ie, while cells are viable); therefore, this procedure is unavailable to most clinicians.


OBJECTIVE
To develop a fixation method for induced sputum samples that allows for a delay in processing while maintaining sample integrity and not altering the standard processing method.


METHODS
Sputum samples were collected and split into three portions: a fresh sample processed using the routine method (within 3 h, using dithiothreitol); fixation in alcohol followed by delayed processing using the routine method (within 48 h to 72 h, using dithiothreitol); and fixation in formaldehyde followed by delayed processing using an alternative method (within 48 h to 72 h, using proteolysis). For each method, cytospins were prepared and differential cell counts were performed.


RESULTS
Fixation in alcohol provides accurate measures of eosinophils and macrophages, but not neutrophils. Formaldehyde fixation provides accurate measures of neutrophils and macrophages, but not eosinophils.


CONCLUSIONS
Alcohol fixation is a superior method for eosinophil quantification. It requires alteration of standardized methods for sputum sample processing and should be recommended for monitoring eosinophilic airway disease in settings where immediate processing of a sputum sample is not possible.
Dorman
Sandra C
SC
School of Human Kinetics, Laurentian University, Ontario. sdorman@laurentian.ca
Bussoli
Melanie A
MA
Ritz
Stacey A
SA
D000328:Adult; D002470:Cell Survival; D003430:Cross-Sectional Studies; D000431:Ethanol; D005260:Female; D005404:Fixatives; D005557:Formaldehyde; D006801:Humans; D008297:Male; D011446:Prospective Studies; D019035:Rural Health Services; D012424:Rural Population; D012997:Solvents; D013048:Specimen Handling / Q000379:methods*; D013183:Sputum / Q000166:cytology*
D005404:Fixatives; D012997:Solvents; D005557:Formaldehyde; D000431:Ethanol