Comparison of Catalytic and Immunological Amylase Tests for Identifying of Saliva from Degraded Samples

The stability of salivary α-amylase is a critical factor in both catalytic and immunological method-based forensic saliva identification. This study aimed to assess the sensitivity of catalytic and immunological tests on degraded saliva samples. Degraded saliva stains were prepared by microbial decomposition using humid soil. Salivary α-amylase activity was catalytically detected both qualitatively and quantitatively using the Phadebas^® amylase test. As immunological methods, we conducted qualitative and quantitative tests using the RSID™-saliva test and ELISA, respectively. Salivary α-amylase activity of degraded samples (incubated at 37°C for 12 h) was significantly lower than that of controls in the quantitative tests. All the degraded samples obtained by the humid soil produced negative results in the Phadebas^® tests, but showed positive results in the RSID™-saliva test and ELISA. These results suggest that immunological tests are effective for testing degraded saliva samples that have lost their enzymatic activity.