Forensic STR analysis reveals DNA contamination previously undetected during clinical analysis of chronically inflamed tissues

Abstract 

While investigating the potential for genetic instability in chronic inflammatory disease, using ulcerative colitis (UC) as a model, we analyzed microsatellite DNA of both pre- and post-surgical affected and histologically normal tissues. These samples were also characterized using the forensic Identifiler^® Multiplex System from ABI. Apparent instability was found in the majority of patients using the clinical panel. This panel assumed all samples were single source, whereas the forensic panel revealed that 57% of samples tested with Identifiler^® were mixtures of more than one contributor. It is likely that DNA contamination occurred during routine histological processing. This contamination could lead to erroneous assessments of instability. Microsatellite analysis is used in tumor characterization and therapeutic determinations. Incorrect determinations could affect patient care. Given the sensitivity and widespread use of molecular tests on biopsies and preserved post-surgical tissues, we recommend that an STR multiplex used for forensic individualization be used prior to diagnostic tests to ensure the sample is from a single source.

Keywords: Microsatellite instability, Loss of heterozygosity, Identifiler, Contamination