What is the Hyams (guaiac-based fecal occult blood test) test?

What is the Hyams Test?

There is no medical test called the "Hyams test" in the colorectal cancer screening literature or in standard medical practice. You may be referring to a guaiac-based fecal occult blood test (gFOBT), which is a well-established screening method for colorectal cancer.

Guaiac-Based Fecal Occult Blood Test (gFOBT)

What It Is

• gFOBT detects blood in stool through the pseudoperoxidase activity of heme or hemoglobin 1
• The test uses guaiac-impregnated slides that change color when blood is present 1
• Common brand names include Hemoccult II and Hemoccult SENSA 1

How It Works

• The test requires collecting 2 samples from each of 3 consecutive bowel movements at home 1
• Samples are applied to guaiac-impregnated cards and developed either in a physician's office or clinical laboratory 1
• The guaiac reagent reacts with the peroxidase-like activity of hemoglobin, producing a blue color change if blood is present 1

Clinical Evidence

• Three large randomized controlled trials demonstrated that annual gFOBT screening reduces colorectal cancer mortality by 15-33% over 8-13 years 1
• Only high-sensitivity gFOBT (sensitivity >70% and specificity >90% for cancer) should be used for screening 1
• The sensitivity of a single gFOBT is low (30-50%), but repeated annual testing can detect up to 92% of cancers 1

Pre-Test Requirements

• Patients must avoid red meat, poultry, fish, and some raw vegetables for 3 days before testing to prevent false positives from dietary pseudoperoxidase activity 1, 2
• NSAIDs and aspirin (>1 adult dose/day) should be avoided for 7 days to reduce false positive results from medication-induced bleeding 2
• Vitamin C exceeding 250 mg should be avoided for 3 days as it can cause false-negative results 2, 3

Critical Pitfalls to Avoid

• Single-sample office FOBT collected after digital rectal examination has unacceptably poor sensitivity (4.9% for advanced neoplasia) and should NEVER be used 2, 3
• Rehydration of gFOBT slides is NOT recommended as it substantially increases false-positive rates and affects test readability 1, 2
• Any positive gFOBT must be followed by colonoscopy, not repeat stool testing 1

Test Performance

• High-sensitivity gFOBT (Hemoccult SENSA) has approximately 64.3% sensitivity for colorectal cancer with 3-sample home testing 2
• Specificity ranges from 86.7-87.5% for high-sensitivity tests 2
• The test must be repeated annually to achieve maximum benefit 1

Comparison with Fecal Immunochemical Tests (FIT)

• FIT has largely replaced gFOBT in many settings due to superior performance characteristics 4
• FIT does not require dietary restrictions and has higher participation rates 5, 4, 6
• FIT demonstrates significantly higher detection rates for advanced adenomas compared to gFOBT 5, 6
• However, gFOBT remains the only stool-based test with randomized controlled trial evidence for mortality reduction 1

Current Recommendations

• Only high-sensitivity gFOBT that have been shown to detect a majority of prevalent colorectal cancer should be used 1
• Annual screening is recommended for average-risk adults aged 50 years and older 1
• Tests should be processed in clinical laboratories rather than physician offices to improve standardization 1, 2

If you were asking about a different test or the term "Hyams" refers to something specific in your context, please clarify and I can provide more targeted information.