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Updates: The most complete version of this article is available at the following location

Copyrights: Copyright © 2014 by author(s) and International College of Human Nutrition and Functional Medicine


Citation: Gingras BA, Duncan SB, Scheuller NJ, Schreckenberger PC. Assessment of diagnostic accuracy of recently introduced

DNA stool screening test.

International Journal of Human Nutrition and Functional Medicine


International Journal of Human Nutrition and Functional Medicine

Photos of Chicago, Illinois, USA

Original Research

• Microbiology • Laboratory Science • Medical Errors • Ethics

Assessment of the Diagnostic Accuracy of Recently

Introduced DNA Stool Screening Test

Bruce A. Gingras



Sara B. Duncan



Nate J. Schueller



Paul C. Schreckenberger



Department of Microbiology IIT Research Institute, Chicago, IL,


Department of Pathology Loyola University Medical Center,

Maywood, IL. #Corresponding Author: Paul C. Schreckenberger, Department of Pathology, Loyola University Medical Center,

2160 S. First Ave. Maywood, IL 60153. Phone: 708-216-5682. Email:

. This work was presented in part at

the 112 General Meeting of the American Society for Microbiology, San Francisco, CA, June 18, 2012. This work was support by a

grant from Doctor’s Data, Inc.


The “gold standard” for detection of enteric pathogens

in stool samples is bacterial culture using a variety of

selective and differential media. However, culture

methods can require several days to complete and are

targeted for the detection of bacteria that can be grown

in culture. There is need for qualitative and quantitative

tests that are more rapid than bacterial culture. Real-

time detection polymerase chain reaction (RTD-PCR)

has been applied for the detection of food-borne

pathogens (12), cancer (3,7,


), genetic diseases (



and infectious diseases (6,




). This method

produced a linear quantitative detection range of 7 logs,

with a lower detection limit of 10


colony-forming units

(CFU)/g tissue or a few copies per reaction. (14)

In 2007, a diagnostic testing laboratory

(“Subject Laboratory”) began offering a stool-

screening test that uses a proprietary DNA method to

identify gut microbiota including anaerobes. The

Subject Laboratory claims that their DNA assessment

is specific, accurate, avoids the pitfalls of sample

transport, reports results as specific numbers, and is

more sensitive than classic laboratory methods. Their

stated cutoff for clinically significant pathogens is 1 x

10³ organisms/gram. The purpose of this study was to

assess the accuracy and specificity of this new testing

modality by conducting a proficiency analysis study

performed by an independent Life Sciences research

organization (IIT Research Institute [IITRI], Chicago).

Materials and Methods

Stool Inoculation

: Human stool was utilized as a

matrix in which to spike known concentrations of

various bacterial pathogens. All samples were prepared

from a human stool pool that served as the consistent

control matrix for all samples. This matrix also

provided a background of normal stool flora and was

used throughout the study. The test platforms were the

Subject Laboratory’s Specimen Collection Kits that

were prepared as instructed by the package inserts. One

gram of stool was added to each of three vials

containing either C&S Medium, 10% Formalin

Fixative, or Nucleic Acid Collection Solution. Each

vial was subsequently spiked with 0.1mL of bacterial

target concentrations at either approximately 1.0 x



CFU/mL or 1.0 x 10


CFU/mL. All samples

including the normal unaltered stool specimen were

shipped to the Subject Laboratory via overnight courier

the same day they were prepared with a request for stool