Salivary acetylcholinesterase as a biomarker for organophosphate exposure

Background Workers exposed to organophosphate (OP) pesticides are required to undergo periodic statutory medical surveillance in several countries. Aim To study the relationship between serum, erythrocyte and saliva acetylcholinesterase (AChE) levels and to explore the use of salivary AChE as potential biomarker for OP exposure. Methods A cross-sectional study was conducted on 19 healthy adult male lead-exposed workers who were undergoing six monthly statutory medical examination. Passive drool saliva samples were collected from each worker. Each blood sample was tested for serum and erythrocyte AChE, and each saliva sample was tested for AChE. Results Among the 19 subjects, the mean (±standard deviation) of salivary, erythrocyte and serum AChE/cholinesterase were 22.7 (±17.4), 17171 (±1467), 8861 (±1876) U/l, respectively. There was a moderate correlation between salivary and erythrocyte AChE (r = 0.42, P = 0.071), but not salivary and serum AChE (r = −0.17, P = 0.48). The level of AChE in saliva was ∼1820 times lower than AChE in erythrocytes. Conclusion It is probably not feasible to use saliva as a replacement for blood for the measurement of AChE levels. This is because of the much lower levels of AChE in saliva relative to erythrocytes, the weak correlation between the two measurements and the previously reported high intra-individual variation of salivary AChE.