FLEXSURE OBT

K961062 · Smithkline Diagnostics, Inc. · KHE · Nov 6, 1996 · Hematology

Device Facts

• Record ID: K961062
• Device Name: FLEXSURE OBT
• Applicant: Smithkline Diagnostics, Inc.
• Product Code: KHE · Hematology
• Decision Date: Nov 6, 1996
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 864.6550
• Device Class: Class 2

Intended Use

The FlexSure® OBT (Occult Blood Test) is a rapid, visually read, qualitative immunochemical chromatographic method for detection of human hemoglobin from blood in fecal samples. Fecal occult blood tests are useful screening aids for detecting primarily lower gastrointestinal (g.i.) disorders that may be related to iron deficiency anemia, diverticulitis, ulcerative colitis, polyps, adenomas, colorectal cancers or other g.i. lesions that can bleed. FlexSure® OBT is recommended for use by health professionals as part of routine physical examinations or when lower g.i. disorders are suspected.

Device Story

FlexSure® OBT is a rapid, qualitative, immunochemical chromatographic test for human hemoglobin in fecal samples. It is used by health professionals in clinical settings to screen for lower gastrointestinal bleeding disorders. The device utilizes an immunochemical method to detect human hemoglobin, providing a visual result. Unlike guaiac-based tests, it is specific to human hemoglobin and does not cross-react with dietary peroxidases or iron, eliminating the need for dietary restrictions. The test output is a visual qualitative result, which assists clinicians in identifying patients requiring further diagnostic evaluation, such as colonoscopy. By detecting occult blood, the device aids in the early identification of colorectal neoplasia and other lower GI pathologies, potentially improving patient outcomes through earlier intervention.

Clinical Evidence

Clinical performance evaluated in average-risk (n=1,734) and high-risk (n=283) populations. In average-risk screening, FlexSure® OBT showed 98.4% specificity for colorectal neoplasia vs 97.2% for Hemoccult®, with a positive predictive value of 15.6% vs 3.9%. In high-risk populations, relative sensitivity for colorectal neoplasia was 55.6% vs 51.1% for Hemoccult®. Specificity in presumed normal subjects was 97.7%. Studies confirmed 100% specificity regardless of diet and in simulated upper GI bleeding scenarios.

Technological Characteristics

Immunochemical chromatographic assay for human hemoglobin. Qualitative visual readout. Does not require dietary restrictions. Designed for professional use.

Indications for Use

Indicated for screening individuals 50 years of age or older for lower gastrointestinal bleeding disorders, including colorectal neoplasia, iron deficiency anemia, diverticulitis, ulcerative colitis, polyps, adenomas, and colorectal cancers.

Regulatory Classification

Identification

An occult blood test is a device used to detect occult blood in urine or feces. (Occult blood is blood present in such small quantities that it can be detected only by chemical tests of suspected material, or by microscopic or spectroscopic examination.)

Special Controls

*Classification.* Class II (special controls). A control intended for use with an occult blood test is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 864.9.

Predicate Devices

• Hemoccult® BRAND Routine Screening Test for Fecal Occult Blood

Submission Summary (Full Text)

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NOV - 6 1996
K961062

# 510(k) SUMMARY OF SAFETY AND EFFECTIVENESS
## FlexSure® OBT Immunochemical Fecal Occult Blood Test

This 510(k) summary of safety and effectiveness information is being submitted in accordance with the requirements of SMDA 1990.

**Manufacturer:** SmithKline Diagnostics, Inc.
1050 Page Mill Rd.
Palo Alto, CA 94303-0105
**Attention:** Ronald J. Schoengold

**Proprietary Name:** FlexSure® OBT

**Classification Name:** Occult Blood Reagent

**Intended Use:** The FlexSure® OBT (Occult Blood Test) is a rapid, visually read, qualitative immunochemical chromatographic method for detection of human hemoglobin from blood in fecal samples. Fecal occult blood tests are useful screening aids for detecting primarily lower gastrointestinal (g.i.) disorders that may be related to iron deficiency anemia, diverticulitis, ulcerative colitis, polyps, adenomas, colorectal cancers or other g.i. lesions that can bleed. FlexSure® OBT is recommended for use by health professionals as part of routine physical examinations or when lower g.i. disorders are suspected.

**Predicate Product:** Hemoccult® BRAND Routine Screening Test for Fecal Occult Blood Manufactured by SmithKline Diagnostics, Inc.

**Performance Summary:** The FlexSure® OBT Immunochemical Fecal Occult Blood Test is substantially equivalent to the predicate device Hemoccult®, sold prior to May 28, 1976. The performance of FlexSure® OBT was verified by sensitivity, specificity, cross reactivity, interference, reproducibility and readability studies in laboratory and clinical settings. Refer to the attached PERFORMANCE CHARACTERISTICS.

Marshall C. McCarty
Manager, Regulatory Affairs

10/28/96
Date
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# 510(k) SUMMARY OF SAFETY AND EFFECTIVENESS
FlexSure® OBT Immunochemical Fecal Occult Blood Test

# PERFORMANCE CHARACTERISTICS

## Background

Fecal occult blood testing (FOBT) is utilized worldwide as a screening aid for persons 50 years of age or older to detect gastrointestinal (g.i.) bleeding disorders. Recent studies indicate that detection of 2 mL or more of daily g.i. blood loss can be an early indicator of significant lower g.i. pathology including colorectal neoplasia (adenomas ≥1cm and colorectal cancers.)

## Analytical Performance Studies

### ANALYTICAL SENSITIVITY:

- Lower Sensitivity Limit - In vitro studies demonstrated that following the recommended procedures for sample collection and storage, FlexSure® OBT reliably detected 0.2 mL or more of added blood per 100 g of feces (0.3 mg hemoglobin per g of stool). This level of blood is approximately equal to 2 to 3 mL of daily in vivo lower g.i. bleeding.

- Prozone Effect - In vitro studies demonstrated that FlexSure® OBT reliably detected up to 17 mL of added blood per 100 g of feces (25 mg hemoglobin per g of stool). At this level and above, blood is generally visible in the stool.

### ACCURACY OF TEST RESULTS:

- Cross Reactivity Studies - Individual fecal samples were spiked with horse myoglobin and hemoglobin from beef, chicken, fish, horse, pig, rabbit, goat, sheep and turkey to determine whether dietary substances cross react with the test. The FlexSure® OBT results were negative even at levels in excess of normal dietary intake or levels which consistently give false-positive results with guaiac-based tests.

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# 510(k) SUMMARY OF SAFETY AND EFFECTIVENESS
## FlexSure® OBT Immunochemical Fecal Occult Blood Test

ACCURACY OF TEST RESULTS (continued):

- **Interference / Effect of Dietary Substances** - Fecal samples from different individuals spiked with excessive quantities of substances known to interfere with guaiac-based tests (plant peroxidases and ferrous iron to check for possible false-positive test results, and a mixture of vitamin C and human hemoglobin to check for possible false-negative test results) yielded 100% accurate test results with FlexSure® OBT.

- **Reproducibility** - The within-site and between-site reproducibility of FlexSure® OBT was demonstrated with a range of blood levels spiked into stool samples to give negative, borderline positive and positive test results. The within-site reproducibility was 100% (90/90). The between-site reproducibility was 97% (30/30 for the negative, 30/30 for the positive and 27/30 for the borderline positive sample).

- **Readability / Repeatability** - Comparable results were obtained with experienced and inexperienced reader groups, each using fecal samples spiked with low to moderate levels of human blood. The results indicated greater than 95% agreement among the two reader groups except at the analytical cutoff of the test where greater variation is expected. The "experienced" group was comprised of three SKD technicians who had used the test extensively, one with a doctorate degree and two with BA/BS degrees. The "inexperienced" group consisted of 16 individuals with varied educational backgrounds from High School to M.D. located in the U.S., Europe, Australia and Canada.

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# 510(k) SUMMARY OF SAFETY AND EFFECTIVENESS
## FlexSure® OBT Immunochemical Fecal Occult Blood Test

### Clinical Performance Studies

#### AVERAGE RISK SCREENING:

- **Apparent Specificity and Positive Predictive Value in a Comparison of Paired Fecal Occult Blood Tests** - The performance of FlexSure® OBT in an average risk screening population of 1,734 individuals on a restricted diet yielded an apparent specificity for colorectal neoplasia of 98.4% (1,702/1,729) for FlexSure® OBT and 97.2% (1,680/1,729) for Hemoccult®. For any lower g.i. pathology, the apparent specificity was 99.0% (1,666/1,682) for FlexSure® OBT and 98.8% (1,661/1,682) for Hemoccult®. The positive predictive value for colorectal neoplasia was 15.6% (5/32) for FlexSure® OBT and 3.9% (2/51) for Hemoccult®.

#### HIGH RISK POPULATION:

- **Sensitivity** - The performance of FlexSure® OBT in a high risk population of 283 individuals with a personal or family history of colorectal cancer or adenomas who were on a restricted diet yielded a relative sensitivity for colorectal neoplasia of 55.6% (25/45) for FlexSure® OBT and 51.1% (23/45) for Hemoccult®. The Negative Predictive Values were not calculated for this group since this parameter is only meaningful in a screening population.

#### STUDIES WITH PRESUMED NORMAL SUBJECTS:

- **Lower G.I. Specificity** - The apparent specificity (an estimate of specificity due to the inability and inappropriateness of performing colonoscopy on individuals with a negative FOBT result) of FlexSure® OBT for lower gastrointestinal pathology using a group of 88 presumed normal young adults was 97.7% (86/88).

- **Effect of Diet** - The specificity of FlexSure® OBT for human hemoglobin in 19 presumed normal subjects on restricted, unrestricted, and rare red meat diets was tested. FlexSure® OBT yielded a specificity of 100% regardless of diet.

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# 510(k) SUMMARY OF SAFETY AND EFFECTIVENESS
## FlexSure® OBT Immunochemical Fecal Occult Blood Test

STUDIES WITH PRESUMED NORMAL SUBJECTS (continued):

- Simulated Upper G.I. Bleeding - The specificity of FlexSure® OBT for lower g.i. bleeding was studied in a group of presumed normal volunteers who ingested their own blood to simulate upper g.i. bleeding. FlexSure® OBT yielded a specificity of 100% in the four individuals who participated in the study.

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