User Manual and Related Findings - FDF Project

User Manual and Related Findings

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NOTE: Lysis Volume

The lysis volume (80 ul) suggested in our protocol was internally validated taking into account 2 issues:

a)   Appropriate relationship lysis volume: assumed cell content.
b)   Criteria supported by several authors (NIST, OCME) in order to perform replicate amplifications to get reliable results. "To avoid or limit the possibility of getting the wrong answer when testing low amounts of DNA, replicate PCR amplifications are performed and a consensus profile developed. The standard practice is to PCR amplify either two or three aliquots of a DNA extract. Alleles that occur more than once (i.e., repeat) in the obtained profiles are deemed "reliable" as they have been reproduced in separate DNA tests".

However, other authors suggested that splitting a sample into fractions (aliquots) increase the analysis limitations, and efforts should be made to concentrate the template as much as possible into one single reaction.

Each laboratory should validate the final lysis volume to be used with  forensic samples, according to the protocol used.

Related Articles That Support Our Findings

A) We recommended the use of our Lysis solution (containing tensoactive substances) for swabbing procedures, and now:

S. M. Thomasma et al. / J. Forensic Sci. Vol. 58, No. 2 (2013) 465-469
The Influence of Swabbing Solutions on DNA recovery from Touch Samples

FIG. 1 - DNA quantity (pg/uL) recovered from touch samples, sorted by swabbing solutions.  
Data presented as mean ± SE (TW = Tween 20, SG = Simple Green®, 409 = Formula 409®, SDS = digestion buffer, TR = Triton X-100). Water, TW, SG, and SDS had n = 23; 409 and TR had n = 25  after outlier removal. * denotes significantly higher yields than water, based on independent samples t-test.

B) We recommended the use of FDF Kit with firearms, and now:

Samuel Nunn / J. Forensic Sci. Vol. 58, No. 3 (2013) 601- 608
Touch DNA Collection Versus Firearm Fingerprinting: Comparing Evidence Production and Identification Outcomes

TABLE  7 - Comparison of fingerprint and TriggerPro findings.

* TriggerPro = DNA Analysis
Partial table.