Abstract: Objective To study the effect of urinary trypsin inhibitor（UTI） on STR genotyping with urinary samples. Methods Midstream urine samples of 5 male and 5 female volunteers were collected respectively, subpackaged, added with different concentration of UTI and stored at -80 ℃. Genomic DNA was extracted from those urinary samples, of which STR profiles were genotyped with IdentifilerTM kit at 8 different time points. Results of genotyping in urinary samples were compared with those of the homogenous blood control samples and the successful rate of genotyping in different group of urinary samples treated with UTI was determined. Results Fifteen STR loci included in Identifiler system were all detected in control blood samples and urinary samples stored for 1 day. STR locus loss was observed and all 15 STR loci disappeared in female urinary samples untreated with UTI while those storage periods prolonged to 3 and 9 days, respectively. However, all 15 STR loci could be detected in female urinary samples treated with UTI and stored for as long as 9 days. No STR loci could be detected in male urinary samples preserved without UTI for 7 days while 9 STR loci detected preserved with UTI for 9 days. There was no significant difference among the average detection ratios of STR loci in female urinary samples treated with UTI at concentrations of 0.2, 0.4 or 0.6 μg/mL and stored for 30 days, mean of which was as high as 0.840 0±0.042 3, statistically higher than that in male urinary samples（0.160 0±0.042 3）. Conclusion Detection rate of STR loci in urinary samples preserved with UTI was increased significantly, which results in prolonging the storage periods of urinary samples for personal identification.

Key words: forensic genetics, urine, individual identification, urinary trypsin inhibitor