Analytical and Clinical Performance of the Polymedco and NS-Plus Automated Analyzers for the testing of Fecal Occult Blood in Stool Samples

1. Performance Characteristics of the NS-Plus Automated Immunochemical Fecal
Occult Blood Test System
Michael Coyle MD*, Craig A Ennis MD*, Syam P. Gaddam MD*, Milton Koch MD*,
Yin Li MS/ME, Sam E. Moussa MD*, Robert Parson MS/MAS, Timothy C. Simmons MD*,
David Vu MPH, Lei Zhang PhD*
*Clinical Investigator
Abstract requests: Robert.Parson@alere.com, Alere - San Diego, Inc., San Diego, CA 92121
AIMS: The aims of the study were: 1) to evaluate the sensitivity (analytical performance) of the
iFOBT Hemoglobin NS-Plus system compared to a commercial reference system, and 2) to assess
the clinical performance of the NS Plus system to detect fecal occult blood in a prospective clinical
study, by evaluating the positive and negative agreement between the NS-Plus system and a
commercial reference system with fecal samples from asymptomatic individuals and symptomatic
patients scheduled for colonoscopy.
BACKGROUND: The iFOBT Hemoglobin NS-Plus Test system (Otsuka / Alfresa) is a discrete
automated, laboratory-based system (Figure 1) for detecting fecal occult blood which may be useful
in screening average risk individual for colorectal cancer. Subjects were instructed to collect two
consecutive fecal samples using sampling probes which fit into specially designed fecal specimen
collection containers with stabilizing fluid (Figure 2), designed for transport to the laboratory.
PRINCIPLE OF THE ASSAY: The NS-Plus analyzer automates the detection of human (h)
hemoglobin (Hb) by an agglutination reaction between a fecal sample containing blood and a
colloidal gold anti-hHb polyclonal antibody conjugate. Aggregates are formed that change the color
and turbidity of the reaction mixture which is measured at two wavelengths, and reported as positive
or negative, based on a preset cutoff of 100 ng hHb/mL.
METHODS: Eighteen previously screened Hb-negative fecal specimens were each spiked with 8
levels of Hb (0, 20, 40, 60, 100, 150, 300, 1200 ng/mL) to create 144 paired fecal specimens,
prepared for testing using the NS-Plus system and a commercial reference system; the testing was
replicated on the same day in 3 geographically separated clinical laboratories. Results were based on
the percent agreement between the two systems at each level of Hb spiked fecal samples. A
prospective multicenter clinical study was designed to evaluate subject acceptance and evaluate the
positive, negative and overall percent agreements between the NS-Plus and a commercial reference
system. Two fecal specimens from a total of 380 individuals at 8 clinical sites in the U.S. were
collected by screenees and tested in parallel on the two systems.
RESULTS: Optimal overall agreement (98.0% positive agreement and 99.3% negative agreement)
was observed at the 100 ng/mL Hb level for both systems, demonstrating that the ability to detect
hHb in spiked fecal specimens at or above the 100 ng/mL cutoff was comparable (Figure 3). A total
of 380 symptomatic and asymptomatic subjects provided fecal specimens for a study comparing the
NS-Plus to a commercial reference system, yielding an overall percent agreement (OPA) of 93.4%,
positive percent agreement (PPA) of 90.0%, and negative percent agreement (NPA) of 93.9% (Table
1). In the group of 245 symptomatic subjects scheduled to undergo colonoscopy, an OPA of 92.7%,
and PPA of 90.9% were observed. In the group of 135 asymptomatic apparent normal individuals,
an OPA of 94.8% and the NPA of 95.3% were observed.
The iFOBT Hemoglobin NS-Plus Test System Is Not Currently Available in the United States

2. CONCLUSIONS: Current studies indicate that the NS-Plus system is an operator-user-friendly,
reliable iFOBT system that can automatically process up to 300 samples per hour. The sensitivity is
comparable to a commercial reference system (p>0.05). The NS-Plus and the commercial reference
system identified comparable numbers of individuals positive for fecal occult blood, in a prospective
evaluation of 380 individuals. Subjects characterized the NS-Plus fecal sample collection method as
“easy to use.” Additional studies are planned to further validate the NS-Plus system.
Figure 1 Figure 2
Figure 3
Table 1 Agreement Analysis from All Evaluable Subjects
Commercial Reference Assay (Cutoff = 100 ng/mL)
NS-Plus (Cutoff = 100 ng/mL) Positive Negative Total
Positive 45 20 65
Negative 5 310 315
Total 50 330 380
PPA (95% CI): 0.900 (0.782, 0.967) NPA (95% CI): 0.939 (0.908, 0.963)
OPA (95% CI): 0.934 (0.904, 0.957)
The iFOBT Hemoglobin NS-Plus Test System Is Not Currently Available in the United States