The Use of Hemastix^® and the Subsequent Lack of DNA Recovery Using the Promega DNA IQ^TM System

Abstract

Following implementation of our automated process incorporating the Promega DNA IQ system as a DNA extraction method, a large number of blood-containing exhibits failed to produce DNA. These exhibits had been tested with the Hemastix reagent strip, commonly used by police investigators and forensic laboratories as a screening test for blood. Some exhibits were even tainted green following transfer of the presumptive test reagents onto the samples. A series of experiments were carried out to examine the effect of the Hemastix chemistries on the DNA IQ system. Our results indicate that one or more chemicals imbedded in the Hemastix reagent strip severely reduce the ability to recover DNA from any suspected stain using the DNA IQ magnetic bead technology. The 3,3',5,5'-tetramethylbenzidine (TMB) used as the reporting dye appears to interact with the magnetic beads to prevent DNA recovery. Hydrogen peroxide does not seem to be involved. The Hemastix chemistries do not interfere in any way with DNA extraction performed using phenol-chloroform. The incompatibility of the Hemastix chemistries on the DNA IQ system forced us to adopt an indirect approach using filter paper to carry out the presumptive test.

New incompatibilities uncovered using the Promega DNA IQ™ chemistry

“…The mechanism appears to be different from that discussed previously for Hemastix® reagent strips and indigo dye where multiple extractions using fresh DNA IQ™ beads resulted in the capture of all DNA available in the lysates [4,5]. It is possible that additional successive extractions with fresh beads may have recovered more of the DNA present in the samples tested herein.…”

“…Reagents used on exhibits at crime scenes or in the forensic laboratory are regularly tested in our laboratory for their compatibility with our automated DNA IQ™-based extraction protocol. In case of an adverse effect, a modification to the standard operating procedures favoring an indirect application of these chemicals on exhibits can be instructed to reduce the loss of DNA [4] or exhibits can be submitted to a different extraction protocol [5].…”

“…It was discovered that specific constituents found in some casework specimen cell lysates exert various levels of competition with DNA for binding onto DNA IQ™ magnetic beads. For instance, reagents from the Hemastix® strip (Bayer HealthCare LLC), a presumptive test for blood used at the crime scene or in the forensic laboratory, were shown to severely reduce or prevent DNA binding onto the DNA IQ™ paramagnetic beads [4]. Competition for binding sites on the DNA IQ™ beads was also demonstrated between DNA and constituents of blood and denim dye molecules [5].…”

Forensic DNA Analysis

“…Since cellular material will be lost through this additional substrate absorption step, very small or faint bloodstains should be cut and not swabbed. In addition, any extraction method must be chosen within the context of sample type and sample treatment to avoid adverse cross-reactions (Poon et al 2009;Dieltjes et al 2011). ing, or combining several STR targets in a single reaction (Butler 2011). Figure 63.1 illustrates the underlying genetic principles of an STR polymorphism and introduces the relevant genetic terms.…”

A Novel Method for Rapid and Selective Extraction of Male DNA from Rape Kits using Alkaline Lysis and Pressure Cycling Technology (PCT)

“…One major limitation of this method is that DNA may be lost during the wash steps if any other materials interfere with the magnetic bead binding. A recent study noted the loss of DNA extracts in a major criminal investigation because the chemicals present in a presumptive test for blood prevented DNA from binding to these beads [97]. this releases the DNA molecules bound to the beads [140].…”