TY - JOUR T1 - A solution to small samples: A method validation study for sputum assay JF - European Respiratory Journal JO - Eur Respir J VL - 44 IS - Suppl 58 SP - P4236 AU - Matthew Butler AU - William Monteiro AU - Lucy Marshall AU - Erol Gaillard Y1 - 2014/09/01 UR - http://erj.ersjournals.com/content/44/Suppl_58/P4236.abstract N2 - Background: Induced sputum differential leukocyte counts as a relatively non-invasive and repeatable measure of airway inflammation have been used to phenotype patients with asthma. However, the current gold standard processing method (1) is not suitable for sputum plugs <100mg. Children frequently generate samples below this limit. We developed a method with a different filtration technique suitable for processing smaller samples.Aim: To compare our modified (small sample) sputum processing method (Method B) with the current gold standard (Method A).Methods: Sputum samples of sufficient quantity from 13 asthmatic patients (age-range 18-68years) were processed simultaneously using both methods. The median sample size used for Method B was 52mg (range 19-82) of sputum plugs. The difference in eosinophil %age between the methods was plotted against the mean result as proposed by Bland et al. (2).Results: The median %age eosinophils obtained using Method A was 4.75% (range 1.0-37.0) and 3.5% (range 0.5-32.6) using Method B. This difference was not statistically significant. There was no evidence of a systematic error. The bias and precision are shown in Figure 1.Conclusions: Our modified method for small samples gives similar results to the gold standard method described. This technique is particularly useful for paediatric studies.References:1) Pavord, I. et al. Thorax 1997; 52:4982) Bland, J. M. et al. Stat Methods Med Res 1999; 8:135. ER -