Physicians' Newsletter Volume 13, Issue 5

In this issue

  1. Fecal Immunochemical Testing for Occult Blood (FIT) - Now Available at BC Biomedical Laboratories
  2. Management of Patients with Acute Coronary Syndromes (ACS)
  3. Dabigatran (Pradax™) Monitoring
  4. Did You Know?
  5. Download PDF of issue

Fecal Immunochemical Testing for Occult Blood (FIT) - Now Available at BC Biomedical Laboratories

FIT KitA newer test (Fecal Immunochemical Test – FIT) for fecal occult blood (FOB) is now available from BC Biomedical Laboratories. This test is based on the immunochemical detection of human globin while the standard biochemical test (guaiac test – gFOBT)detects peroxidase activity of hemoglobin and possibly other peroxidase-containing substances in stool. Human globin is normally digested in the small intestine so its presence in stool is more specific for blood originating in the lower gastrointestinal tract. The sensitivity for detecting clinically significant colorectal neoplasms is similar between these two methods, particularly if done on two or more separate patient samples, probably because some colorectal neoplasms bleed only intermittently. For this reason we recommend testing two samples collected successively rather than a single sample.

Annual fecal occult blood tests offer an important screening modality for colorectal cancer (CRC) in asymptomatic patients between the ages of 50 and 75 years with no known risk factors (see Clinical Practice Guideline - Detection of Colorectal Neoplasms in Asymptomatic Patients - www.bcguidelines.ca). When performed for CRC screening, patients with stools containing occult blood require a diagnostic workup with colonoscopy to examine the entire colon in order to exclude cancers and polyps, as well as to identify other possible causes of intestinal bleeding (e.g. colitis). Since there are less interfering substances, the FIT test might lead to less follow-up testing of falsely positive test results.

The advantages of FIT testing over guaiac (gFOBT)are:

  • No dietary or medication restriction before or during sample collection
  • The need for two rather than three samples
  • The collection kit is simpler to use.

These advantages should make for better patient acceptance and compliance for fecal testing.

The disadvantage of FIT testing over gFOBT is the cost. Results of on-going studies examining the cost-benefit of FIT in case finding of CRC in population screening programs compared to all other diagnostic modalities have not yet been published. Fecal immunochemical testing (FIT) is not funded by MSP. Until such time as MSP approves a fee code for FIT Testing, the test (two samples) is offered by BC Biomedical Laboratories on a patient self-pay basis at $30.

To order this test, enter FIT or immunochemical occult blood on the patient’s laboratory requisition. Patients then bring the requisition to the laboratory where they are given the instructions and materials necessary for collection at their convenience. Following collection, we ask them to return both samples to the laboratory for analysis.

In the event the patient does not wish to pay for the FIT test, the standard guaiac test will be substituted. The standard guaiac fecal occult blood test funded by MSP is routinely available by checking the fecal occult blood box on the laboratory requisition in the usual way.

Collection instructions for both the gFOBT and FIT test are available in the Patient Instructions section of our website, or use the links below.

Please direct questions to any member of the Medical Biochemistry Group at 604-507-5000.


Management of Patients with Acute Coronary Syndromes (ACS)

Referral of patients with suspected ACS to laboratories for ECG or troponin testing is not recommended (see the Clinical Practice
Guideline, Acute Chest Pain-Evaluation and Triage - www.bcguidelines.ca) Such patients are best sent directly to an Emergency Department for evaluation and management. While BC Biomedical Laboratories does offer Troponin I testing, its use should be restricted to follow-up of known ACS patients, and for very selected, low-risk patients as a “rule-out” test.

Please direct questions to any member of the Medical Biochemistry Group at 604-507-5000.


Dabigatran (Pradax™) Monitoring

Dabigatran (Pradax™) is an oral, direct thrombin inhibitor recently approved by Health Canada for the prevention of thromboembolic disease in patients with atrial fibrillation.

Routine monitoring of Pradax™ is NOT required as it has predictable pharmacokinetics.

BC Biomedical Laboratories continues to receive orders for PT(INR) and aPTT in patients receiving this drug.

Please note:

  • The PT(INR) is INSENSITIVE to Pradax™ and should NOT be used.
  • The aPTT can be used but is relatively insensitive. There is poor correlation between the value of the aPTT and level of Pradax™. Typically, the amount of drug present can be predicted based on its half-life (~13 hours) assuming normal renal function. Therefore, often laboratory assessment using the aPTT is NOT required and the amount of drug present can be predicted to decrease to 5-10% plasma levels after simply discontinuing the drug for 48 hours. This may be indicated prior to elective surgery but should be assessed on a case by case basis.

Please direct any questions/concerns to any member of the Hematopatholgy Group at 604-507-5000.


Did You Know?

  • Lactate dehydrogenase (LD) is primarily used to monitor some hematological neoplasms and hemolytic anemias. It is NOT a useful test for the investigation of suspected liver disease.
  • Celiac disease is common not only in patients of European extraction, but also in those whose familiy origin is from South Asia, Middle East; North, West and East Africa; and South America.
  • A low mean cell hemoglobin (MCH) value usually signifies iron deficiency and/or a hemoglobinopathy/thalassemia trait. In iron deficiency, the MCH often is the first CBC parameter to fall, even before the MCV or hemoglobin are affected.

 

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