OnSite FOB Rapid Test

Hemoglobin VariantsHemoglobin variants are a part of the normal embryonic and fetal development, but may also be pathologic mutant forms of hemoglobin in a population Function • Hemoglobin A (α2β2) – The most common with a normal

amount over 95%• Hemoglobin S (α2βS

2) – A variant form of hemoglobin found in people with sickle cell disease, not uncommon in USA • Hemoglobin H (β4) – A variant form of hemoglobin, formed by

a tetramer of β chains, which may be present in variants of α thalassemia.• ………………..

Hemoglobin Structure

Benefit of FOB Detection • Detection of gastrointestinal (GI) bleeding facilitates early diagnosis of GI track cancer

• FOB testing is recommended annually by the American Cancer Society (2001) for average-risk women and men, 50 years of age and older. However, patients with significant risk factors such as family history of colorectal cancer should be screened earlier and more often.

Methods

•Biochemical method -Guaiac • False positive guaiac results may occur from a diet

of red or rare meats and/or dietary peroxidases.• Vitamin C (ascorbic acid) may cause false negative

results.

• Fecal Hb detection - Immunological • May fail to detect upper gastrointestinal tract bleeding,

producing a false negative result • Mabs recognize single antigenic determinants and may not react

positively with genetic variants of human hemoglobin, such as occur in sickle cell disease

Analytical Performance Characteristics • Sensitivity of Immunological Tests to Hemoglobin Variants

Mabs equivalently recognizes variants of hemoglobin (e.g., hemoglobin SS and hemoglobin CC) in whole blood samples from persons with hemoglobinopathies that are prevalent in the United States

• Interference • Hemoglobin from beef, chicken, fish, horse, pig, rabbit, goat, and sheep • Myoglobin or ground up meat extracts prepared from beef, chicken, fish,

horse, pork or ham, rabbit, goat, and sheep

• Cut-off • Reproducibility (Qualitative Tests)• Prozone (Hook) Effect (Immunological Tests)• Stability • Test kit stability • Specimen collection and handling

• Quality Control

Analytic Sensitivity

• 200 ng/ml : low false positive • 50 ng/ml : intermediate sensitivity• 25 ng/ml : high sensitive, high positivity rate

Factors Impact Test Performance • Representative fecal sample• Cause False negative • Solution: Randomly in 5-6 spots

• Too much fecal matters picked up • No flow migration • Solution: Sample limiting device and warning

Limitations • Results are not conclusive evidence of the presence or

absence of gastrointestinal bleeding or pathology.

• Test results can only be regarded as a preliminary screening or as an aid to diagnosis. It is not intended to replace other diagnostic procedures such as colonoscopy, sigmoidoscopy, or other x-ray studies.

• Because gastrointestinal lesions may bleed intermittently and blood in feces is not distributed uniformly, a negative test result does not assure absence of lesions.

• Any positive result should be followed up with further studies to establish the source of bleeding.

Limitations

Hemoglobin protein tends to be altered chemically as it passes through the GI tract, changing its antigenicity.

A test may detect occult blood when it is the result

of lower gastrointestinal tract bleeding, but may fail to detect upper gastrointestinal tract bleeding, producing a false negative result.

Risk to Health Failure of an FOB test to perform as indicated, or error in interpretation of results, may lead to improper patient management, including misdiagnosis and inappropriate treatment. For example, false negative results from an FOB test in patients who have asymptomatic cancer, adenoma, or other conditions could potentially give false reassurance and cause a delay in reporting symptoms and thus delay initiating treatment. False positive results could lead to performing unnecessary procedures (e.g., colonoscopy).

Conditions that are known to lead to false test results: • Intermittent bleeding and irregular distribution of blood in the feces may contribute to false negative results.

• Certain drugs such as aspirin and non-steroidal anti-inflammatory drugs may increase gastrointestinal bleeding and cause positive results. Iron compounds have been reported to cause false positive results. Ascorbic acid (vitamin C) taken at levels greater than 250 mg/day can cause false negative guaiac test results. Vitamin C in excess of 250 mg from either supplements or citrus fruits and juices should be avoided for three days before testing (Reference1).

• The American Cancer Society cautions that a single FOB test done during a digital rectal exam in the doctor’s office is not sufficient for screening. The risk of a false negative result is mitigated by performing three separate tests on three consecutive bowel movements.

CTK FOB Test Complaint Review

11 complaints over 7 years: • Too sensitive led to false positive (2 cases) • 25 ng/ml test

• Test result was not consistent among different lots (1 case)• Fecal extraction buffer leakage (Main complaints)

FOB Rapid Test Quality Requirement • False positive is not good • False negative is not good• Recognizes variants of hemoglobin (e.g., hemoglobin

SS and hemoglobin CC) in whole blood samples from persons with hemoglobinopathies that are prevalent in the United States (e.g., sickle cell disease).

Offering the Right FOB Test We needs to understand

• Sensitivity requirement • The action to be taken for positive result • Leading competitor product on the market

Together, we grow Athenese Dx & CTK

Early Diagnosis for a better life

Together, we grow Athenese Dx & CTK

Athenese DX contact information:

Module # 407 & 408, 4th Floor,Ticel Bio Park II, No. 5, CSIR Road,

Taramani, Chennai - 600113,TamilNadu, India.