Kanlayanee TangprasertNattinee JantaratnotaiPraewpat PachimsawatMahidol University2020-01-272020-01-272019-11-01American Journal of Human Biology. Vol.31, No.6 (2019)15206300104205332-s2.0-85069719718https://repository.li.mahidol.ac.th/handle/20.500.14594/49707© 2019 Wiley Periodicals, Inc. Objectives: A handheld biosensor for measuring salivary α-amylase (sAA) was developed for convenient on-site measurement. Previous studies reported some discrepancies in sAA levels measured with a biosensor and a standard assay. This study aimed to compare sAA levels measured with three different methods and the factors affecting its levels. Methods: Thirty-eight participants collected saliva two times for three measurements. First, the collector strip was placed under the tongue for 2 minutes, then the strip was used to measure sAA level on-site immediately (intraoral biosensor; method 1). Then, a participant pooled the saliva for 4 minutes and collected the saliva into the tube which was aliquoted to measure in a laboratory with a handheld biosensor (extraoral biosensor; method 2) and with a standard enzyme kinetic assay (EKA; method 3). Additional experiments were carried out to compare the levels of sAA measured with differences in pooling time and positioning of the collector strip. Results: A high correlation of sAA levels between an extraoral and an EKA measurement (r = 0.989) was observed, while sAA levels measured with an intraoral method showed a significant but weaker correlation with either an EKA (r = 0.475) or an extraoral method (r = 0.436). Saliva pooling time and positioning of the collector strip significantly affected sAA levels. Conclusions: A handheld biosensor is valid to measure sAA levels extraorally. For an intraoral measurement, pooling time and positioning of the collector strip need to be taken into account.Mahidol UniversityAgricultural and Biological SciencesBiochemistry, Genetics and Molecular BiologyMedicineArticleSCOPUS10.1002/ajhb.23298