One Step FOB Test Strip for feces (Revised Jan. 30th, 2001)
Intended Use The one step FOB (Occult Blood) test is a simple one step immuno-chromatographic assay for the rapid, qualitative detection of human occult blood in feces.
Explanation of the Test: The FOB test is designed to detect lower levels of fecal occult blood than standard guaiac tests. The basis of the test is an immuno-chromatographic sandwich capture method, which yields results that appear more specific to human occult blood and are easier to interpret than those of guaiac-based devices. In addition, unlike guaiac assays, the accuracy of the OB test is not affected by interfering substances and does not depend on the status of the patient at the time the specimen is taken.
The Fecal Occult Blood Test employs a unique combination of monoclonal and polyclonal antibodies to selectively identify occult blood in test samples with a high degree of sensitivity. Elevated levels of human occult blood as low as 25 ng/ml can be detected.
Precautions The One Step FOBtest kit should be stored at room temperature 4-30oC (40-86oF). The test device is sensitive to humidity and as well as to heat. Perform the test immediately after removing the test device from the foil pouch. Do not use it beyond the expiration date.
Warnings 1. For in vitro diagnostic use only. 2. Do not eat or smoke while handling specimens. 3. Wear protective gloves while handling specimens. Wash hands thoroughly afterwards. 4. Avoid splashing or aerosol formation. 5. Clean up spills thoroughly using an appropriate disinfectant. 6. Decontaminate and dispose of all specimens, reaction kits and potentially contaminated materials, as if they were infectious waste, in a biohazard container. 7. Do not use the test kit if the pouch is damaged or the seal is broken.
Specimen preparation 1. Specimen collection should not be performed during or within three days of a menstrual period, or if the patient suffers from bleeding hemorrhoids or blood in the urine, false-positive test results may be obtained. 2. Dietary restrictions are not necessary. 3. Alcohol, aspirin and other medications taken in excess may cause gastrointestinal irritation resulting in occult bleeding. Such substances should be discontinued at least 48 hours prior to testing.
Specimen collection 1. Unscrew the top of the sample collection device and use the sample collection stick to collect stool sample by dipping the stick into 3 different places of the same stool sample. 2. Put the sample collection stick containing the sample back in the sample collection device and screw it tightly. Shake it very well. 3. It is recommended that the above Step 1 to Step 2 to be repeated for three consecutive days.
Procedure of the test 1. Remove the test strip from its foil pouch. 2. After collecting stool samples for three consecutive days, bring the sample collection device to room temperature. Then shake the device several times. 3. Break off the tip of the collection device and squeeze 2 drops of the extracted sample on the sample pad (Figure 1). 4. Interpret test results at 5 to 10 minutes.
Caution: The above interpretation time is based on reading the test results at room temperature of 15 to 30 oC. If your room temperature is significantly lower than 15 oC, then the interpretation time should be properly increased.
Interpretation of the test 1. A color band will appear at the left section of the result window to show that the test is working properly. This band is the Control Band. 2. The right section of the result window indicates the test results. If another color band appears at the right section of the result window, this band is Test Band.
Positive Result: The presence of two color bands (“C” and “T” bands) within the result window no matter, which band appears first indicates a positive result (Figure 2).
Negative Result: The presence of only one purple color (“C”) band within the result window indicates a negative result (Figure 2).
Invalid result: After performing the test and no purple color band is visible within the result window, this result is considered invalid. The directions may not have been followed correctly or the test may have deteriorated. It is recommended that the specimen be re-tested (Figure 2).
Note: Once a positive result has been established (after 10 minutes), the result will not change. However, in order to prevent any incorrect results, the test result should not be interpreted after 10 minutes. Interpreting test results after 10 minutes, the sensitivity of the test will be higher than 25 ng/ml..
Limitations of the test The presence of blood in stools may be other than colorectal bleeding, such as hemorrhoids, blood in urine or stomach irritations. Negative results do not exclude bleeding since it can be intermittent. Colorectal polyps at very early stages may not bleed. Other clinically available tests are required if questionable results are obtained. As with all diagnostic tests, a definitive clinical diagnosis should not be based on the results of a single test, but should only be made by the physician after all clinical and laboratory findings have been evaluated.
References 1. Bahrt KM, Korman LY, and Nashel DJ, “Significance of a Positive Test for Occult Blood in Stools of Patients Taking Anti-inflammatory Drugs,” Arch Intern Med, 1984, 144:2165-6. 2. Blebea J and McPherson RA, “False-Positive Guaiac Testing With Iodine,” Arch Pathol Lab Med, 1985, 109:437-40. 3. Block GE, “Colon Cancer: Diagnosis and Prognosis in the Elderly,” Geriatrics, 1989, 44(5):45-7, 52-3. 4. Doyle AC, “A Study in Scarlet,” Philadelphia, PA: JB Lippincott Co, 1902. 5. Fleischer DE, Goldberg SB, Browning TH, et al, “Detection and Surveillance of Coleorectal Cancer,” JAMA, 1989, 261(4):580-5.