The effect of cotton-based collection methods on eosinophil cationic protein (ECP) concentrations detected in saliva

BACKGROUND Salivary eosinophil cationic protein (ECP) level has the potential to be an assessment tool for asthma. Its measurement is not well-established and needs standardization. We studied how passive drool (PD) and two commercial devices, Salivette(®) (cotton-based device) and Sorbette(®) (cellulose-cotton-based-device), may affect ECP levels during collection among healthy subjects. METHODS Study I (n = 10) involved direct sampling of healthy adult subjects with Salivette(®) and Sorbette(®). Study II (n = 33) involved 'indirect' sampling of previously collected PD by both devices. RESULTS In study I, ECP levels were detected in all PD samples but only in three with Sorbette(®) and none with Salivette(®) (collection order: PD, Sorbette(®) and Salivette(®)). We changed the order of collection (Salivette(®), Sorbette(®), PD) and the results were similar (ECP levels detected in all PD samples, three with Sorbette(®) and only one with Salivette(®)). In study II, ECP levels in saliva collected by PD was 12.8 μg/L (median) and using Sorbette(®) and Salivette(®) were < 2.0 μg/L and 3.4 μg/L respectively (p < 0.01). ECP levels in PD correlated with Sorbette(®) (r(s) = 0.79, p < 0.01) and Salivette(®) (r(s) = 0.62, p < 0.01). CONCLUSION Compared to PD, saliva collected using cotton or cellulose-based collection devices resulted in lower measurable ECP levels.