Clinical Indications

Suspicion for APS in patients with an elevated aPTT, unexplained thrombocytopenia, or a history of arterial and venous thrombosis and/or obstetric complications.

Interpretation

Lupus Anticoagulant (LA)
Tests for LA are interpreted as positive, indeterminate or negative. A narrative interpretation is issued for each patient panel:

Anticardiolipin Antibodies and B2GP1 Antibodies
Tests for ACA and B2GP1 are interpreted as positive, equivocal, or negative. The reference range of each test in the diagnostic panel is shown in Table 1.

Methodology

Laboratory testing for LA consists of a panel of assays (at least two assays on different principles in each criterion) specifically performed together to maximize diagnostic potential.

Abbreviations:

Limitations

LAs are heterogeneous in terms of antigenic recognition, and aPTT reagents are variable in terms of phospholipid composition. Thus, variability in detection of LAs may exist between individual reagents, between different panel tests, and/or between laboratories.

Consequently, a normal aPTT cannot definitively exclude the presence of an LA; therefore, if clinical suspicion is high, the full panel may be performed.

Both ACA and B2GP1 APA assays are recommended as using one B2GP1 antibody assay can miss some cases of APA.

Table 1: Reference Ranges of Each Test in the Lupus Anticoagulant Diagnostic Interpretive Panel

References

1. Pengo V, Tripodi A, Reber G, et al. Update of the guidelines for lupus anticoagulant detection. J. Thromb Haemost. 2009: 7:1737.

2. Kottke-Marchant K. An Algorithmic Approach to Hemostasis Testing. CAP Press (2008).

3. Miyakis S, Lockshin MD, Atsumi T et al. International consensus statement on an update of the classification criteria for definite antiphospholipid antibody syndrome (APS). J. Thromb Haemost. 2006; 4:295.

4. Moffat KA, Ledford-Kraemer MR, Plumhoff EA et al. Are laboratories following published recommendations for lupus anticoagulant testing? An international evaluation of practices. Thromb Haemost. 2009:101:178.

5. Hoppensteadt D, Walenga J. The relationship between the antiphospholipid syndrome and heparin-induced thrombocytopenia. Hematol Oncol Clin N Am. 2008:22:1.

Clinical Indications

CALR mutation testing is useful in the workup of suspected myeloproliferative neoplasms, especially those that are negative for JAK2 V617F.

Interpretation

Normal results are reported as “CALR mutation not detected.”

Positive results are reported as “CALR mutation detected,” and an interpretation is provided that includes a description of the mutation (type 1, type 2, or other).

Methodology

Genomic DNA is extracted from the sample and CALR exon 9 is amplified by PCR. Fragment length analysis is performed to assess for insertion/deletion mutations.

Limitations

This assay has a sensitivity of 5% mutant alleles. This assay detects only insertion/deletion mutations in CALR exon 9, and a negative result does not exclude the possibility of a myeloproliferative neoplasm.

References

1. Swerdlow SH, Campo E, Harris NL, et al. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. Lyon: IARC Press; 2008.

2. Nangalia J, Massie CE, Baxter EJ, et al. Somatic CALR mutations in myeloproliferative neoplasms with nonmutated JAK2. N Engl J Med. 2013;369:2391-405.

3. Klampfl T, Gisslinger H, Harutyunyan AS, et al. Somatic mutations of calreticulin in myeloproliferative neoplasms. N Engl J Med. 2013;369:2379-90.

4. Tefferi A, Lasho TL, Finke CM, et al. CALR vs JAK2 vs MPL-mutated or triple-negative myelofibrosis: clinical, cytogenetic and molecular comparisons. Leukemia. 2014;28:1472-7.

5. Tefferi A, Wassie EA, Lasho TL, et al. Calreticulin mutations and long-term survival in essential thrombocythemia. Leukemia. 2014;28:2300-3.

6. Rumi E, Pietra D, Pascutto C, et al. Clinical effect of driver mutations of JAK2, CALR, or MPL in primary myelofibrosis. Blood. 2014;124:1062-9.

7. Rumi E, Pietra D, Ferretti V, et al. JAK2 or CALR mutation status defines subtypes of essential thrombocythemia with substantially different clinical course and outcomes. Blood. 2013;123:1544-1551.

Clinical Indications

MYD88 L265P mutation testing is useful in the evaluation of small B-cell neoplasms, especially those with plasmacytic differentiation.

Interpretation

Methodology

DNA is extracted from the sample. Real-time PCR is performed using primers specific for the L265P mutation and a reference primer set for a non-mutated portion of the MYD88 gene.

Limitations

This assay has a sensitivity of 0.5% mutant alleles.

This assay detects only the L265P point mutation, and a negative result does not exclude a diagnosis of lymphoplasmacytic lymphoma.

References

1. Swerdlow S.H., Berger F., Pileri S.A., et al. Lymphoplasmacytic lymphoma. In: WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. IARC: Lyon 2008. Swerdlow SH, Campo E. Harris EL, et al (Eds). Pp 194-195.

2. Treon SP, Hunter ZR, Castillo JJ, et al. Waldenström macroglobulinemia. Hematol Oncol Clin North Am. 2014 Oct;28(5):945-70.

3. Treon SP, Xu L, Yang G, et al. MYD88 L265P somatic mutation in Waldenström’s macroglobulinemia. N Engl J Med. 2012 Aug 30;367(9):826-33.

4. Hamadeh F, MacNamara SP, Aguilera NS, et al. MYD88 L265P mutation analysis helps define nodal lymphoplasmacytic lymphoma. Mod Pathol. 2014 Sep 12. [Epub ahead of print]

5. Ondrejka SL, Lin JJ, Warden DW, et al. MYD88 L265P somatic mutation: its usefulness in the differential diagnosis of bone marrow involvement by B-cell lymphoproliferative disorders. Am J Clin Pathol. 2013 Sep;140(3):387-94.

Clinical Indications

The ADAMTS13 activity (ADM13A), inhibitor (ADM13I), and autoantibody (ABADM) assays are useful for the diagnosis of the congenital or acquired form of TTP.

Interpretation

Diagnosis of TTP is difficult, due to the rarity of the disease and the poor specificity of clinical and laboratory signs and symptoms. Decreased ADAMTS13 activity (less than 68%) can be observed in idiopathic (autoimmune-related) TTP, TMA syndrome, congenital ADAMTS13 deficiency (Upshaw Schulman syndrome) and secondary to other clinical conditions such as HUS, ITP, solid organ or bone marrow transplantation, sepsis, DIC, HIV infection, inflammation, bloody diarrhea, liver disease, pregnancy, malignancy, or certain drug effects (e.g., clopidogrel, cyclosporine, mitomycin C, ticlopidine, tacrolimus, etc.).

1. Normal ADAMTS13 activity (>=68%) and negative ADAMTS13 inhibitor (<=0.4 IU):
No laboratory evidence of TTP

2. Mildly decreased ADAMTS13 activity (30-67%) and negative ADAMTS13 inhibitor (<=0.4 IU):
Unlikely idiopathic TTP by laboratory findings and suggestive of TTP secondary to other clinical conditions. However, if there is a strong clinical suspicion of idiopathic TTP, autoantibody assay can be performed

3. Mildly decreased ADAMTS13 activity (30-67%) and positive ADAMTS13 inhibitor (>0.4 IU):
Diagnostic of idiopathic TTP or prior therapy effect in TTP patients

4. Decreased ADAMTS13 activity (<30%) and positive ADAMTS13 inhibitor (>0.4 IU):
Diagnostic of idiopathic TTP

5. Decreased ADAMTS13 activity (<30%) and negative ADAMTS13 inhibitor (<=0.4 IU):
Further evaluation of ADAMTS13 autoantibody assay

a) Positive ADAMTS13 autoantibody (>18 U/mL):
Diagnostic of idiopathic TTP

b) Negative ADAMTS13 autoantibody (<=18 U/mL):
Suggest ADAMTS13 sequencing to rule out congenital TTP with positive ADAMTS13 gene mutation

Methodology

ADAMTS13 activity is measured by change of fluorescence energy transfer (FRET) technology with recombinant VWF86 substrate (American Diagnostica Inc/Sekisui, Stamford, CT) in citrated plasma. The basic principle of the method is that proteolytic cleavage of the VWF86-ALEXA FRET substrate between the Tyr-Met residues by ADAMTS13 uncouples the ALEXA fluorochromes resulting in an increase in fluorescence.

ADAMTS13 inhibitor is measured by using a mixing study. After the patient’s plasma is mixed with normal pooled plasma (1:1) and incubated for 1 hour at 37°C, the residual ADAMTS13 activity of the mixture is measured using FRET technology. ADAMTS13 inhibitor level (Bethesda Unit) is calculated. One inhibitor unit is considered as the concentration of inhibitor that can reduce ADAMTS13 activity by 50%.

ADAMTS13 autoantibody is measured by sandwich enzyme immunoassay modified from Technozym ADAMTS13 INH kit (Technoclone Inc, Vienna, Austria). After binding with pre-coated recombinant human ADAMTS13, anti-ADAMTS13 IgG and conjugate, resulting color is measured photometrically. The color intensity is proportional to the concentration of ADAMTS13 IgG antibodies.

Limitations

ADAMTS13 activity by FRET-based assay can be interfered by high levels of endogenous VWF, hyperlipemia, elevated plasma hemoglobin level (>2 g/dL; potent inhibitor of ADAMTS13), hyperbilirubinemia (>15 mg/dL) or other proteases that may cleave ADAMTS13. In addition, recent plasma exchange or transfusion can potentially mask the diagnosis of TTP because of false normalization of ADAMTS13 activity. ADAMTS13 autoantibody assay, usually measuring IgG by enzyme immunoassay, is sensitive but less specific than functional inhibitor assay, and can be detected in other immune-mediated disorders such as systemic lupus erythematosis, antiphospholipid syndrome or patients with high titer of IgG, and some healthy individuals (10-15%).

Suggested Reading

1. Just S. Methodologies and clinical utility of ADAMTS-13 activity testing. Semin Thromb Hemost. 2010;36:82-90.

2. Kremer Hovinga JA, Mottini M, Lammle B. Measurement of ADAMTS-13 activity in plasma by the FRETS-VWF73 assay: comparison with other assay methods. J Thromb Haemost. 2006;4:1146-8.

3. Reyvand F, Palla R, Lotta LA et al. ADAMTS13 assays in thrombotic thrombocytopenic purpura. J Thromb Haemost. 2010;8:631-640.

4. Sadler JE. Von Willebrand factor, ADAMTS13, and thrombotic thrombocytopenic purpura. Blood. 2008;112(1):11-8.

5. Rieger M1, Mannucci PM, Kremer Hovinga JA et al. ADAMTS13 autoantibodies in patients with thrombotic microangiopathies and other immunomediated diseases. Blood. 2005;106(4):1262-7.

6. Kremer Hovinga, Lämmle B. Role of ADAMTS13 in the pathogenesis, diagnosis, and treatment of thrombotic thrombocytopenic purpura. Hematology Am Soc Hematol Educ Program. 2012;2012:610-6.

7. Barrows BD, Teruya J. Use of the ADAMTS13 activity assay improved the accuracy and efficiency of the diagnosis and treatment of suspected acquired thrombotic thrombocytopenic purpura. Arch pathol Lab Med. 2014;138:546-9.

Clinical Indications

Patients with a personal or family history of unexplained or recurrent thrombosis and/or pregnancy complications.

May potentially be of benefit for screening patients who will be placed at increased risk of thrombosis.

Interpretation

This panel of tests is not simply reported as positive or negative; a narrative interpretation is issued for each patient panel.

Each test is reported separately, taking into account the patient’s clinical context.

Each positive test result increases the relative risk of thrombophilia independently of the other test results.

Limitations

Results from a hypercoagulability workup are difficult to interpret in the setting of acute thrombosis or anticoagulant medication therapy; thus, testing should be performed approximately 30 days after VTE or discontinuation of medication including warfarin, heparin, direct thrombin inhibitors (DTIs), and fibrinolytic agents.

Other clinical conditions (e.g. pregnancy, inflammatory states, liver disease, etc.) may affect certain assay results as well. The test requestor should provide appropriate clinical information in regards to these conditions to assist the laboratory in making the best possible interpretation of results. Alternatively, thrombophilic testing may be delayed until these clinical conditions have subsided.

Rarer thrombophilic mutations do exist for which testing is not currently performed. In this case, a patient may have an apparently-negative thrombophilic workup while still exhibiting a thrombotic phenotype. Clinical judgment is necessary to guide the therapy of these patients.

Methodology

Laboratory testing for thrombophilia consists of a panel of assays specifically performed together to maximize diagnostic potential.

Key:

Abbreviations:

Functional Testing

Antigenic Testing

Genetic/Molecular Testing

References

1. Colman RW et al. Hemostasis and Thrombosis: Basic Principles and Clinical Practice, 5th Ed. Lippincott Williams and Wilkins (2006).

2. Heit J. Thrombophilia: Common Questions on Laboratory Assessment and Management. Hematology. 2007;127-35.

3. Kottke-Marchant K. An Algorithmic Approach to Hemostasis Testing. CAP Press (2008).

Clinical Indications

Testing rules out venous thromboembolism, DVT, or pulmonary embolism in the presence of risk factors and clinical symptoms.

Interpretation

Negative: D-dimer < 500 ng/ml

Limitations

D-dimer should not be used as a stand-alone test.

Elevated D-dimer may be due to recent surgery, trauma, or infection.

Elevated levels are also seen with liver disease, pregnancy, eclampsia, cardiovascular disease, and some cancers.

Suggested Reading

1. Bockenstedt P. D-Dimer in Venous Thromboembolism. N Engl J Med. 2003;349:1203-1204.

2. Stein PD, Matta F. Acute pulmonary embolism. Curr Probl Cardiol. 2010 Jul;35(7):314-76.

3. Salaun PY, Couturaud F, LE Duc-Pennec A, Lacut K, LE Roux PY, Guillo P, Pennec PY, Cornily JC, Leroyer C, LE Gal G. Non-invasive diagnosis of pulmonary embolism. Chest. 2010; Aug.19, e-pub ahead of print.

Clinical Indications

The functional activity of VWF traditionally has been assessed using the ristocetin cofactor activity (RiCof) assay, which measures the VWF-mediated agglutination of platelets in the presence of ristocetin. However, the usefulness of this assay has limitations due to poor reproducibility and lack of calibration. The collagen-binding activity (CBA) assay has been proposed as a supplemental test for VWF activity.

The CBA assay is based on the ability of multimeric forms of VWF to bind collagen, and its greatest strength lies in the ability to selectively detect primarily high molecular weight (HMW) forms of VWF, which are known to be most functional and adhesive.

The CBA assay is a useful adjunctive to the RiCof assay for the diagnosis of VWD and to differentiate VWD with deficiency of HMW multimer forms in type 2A and type 2B from type 1. It also can differentiate very low levels of VWF in severe type 1 from a complete absence of VWF in type 3 and has been reported as a better marker for therapeutic efficacy of treatment with DDAVP® (desmopressin) and fVIII concentrate.

Interpretation

CBA results are reported as % of the reference value for CBA. CBA to VWF:Ag ratio is calculated to provide a ratio of VWF activity to protein amount.

1. Type 1 VWD patients have concordantly decreased CBA and VWF:Ag levels.

2. Type 3 VWD patients have markedly decreased or nearly absent CBA and VWF:Ag levels.

3. Type 2A VWD and type 2B VWD patients have discordantly decreased CBA and VWF:Ag levels with markedly decreased CBA level, normal, or decreased VWF:Ag level and loss of HMW multimers.

4. Type 2M VWD patients have a discordantly decreased CBA level with a normal or decreased VWF:Ag level but without the loss of HMW multimers.

5. Type 2N VWD patients have normal CBA and VWF:Ag with discordantly decreased FVIII coagulant activity.

6. CBA values are known to be lower in O blood groups compared with non-O blood groups. However, as VWF:Ag levels show similar blood group dependence, the ratio of CBA/VWF:Ag is not affected.

Methodology

The CBA assay is an enzyme immunoassay (REAADS® Collagen Binding Assay ELISA kit, Corgenix, Inc., Broomfield, Colo.) that quantitates the binding of VWF to a collagen-coated microwell plate. After binding peroxidase-conjugated anti-VWF antibodies to VWF multimers, the resulting color intensity is determined photometrically, which is proportional to HMW forms of VWF present in the plasma. In situ evaluation for precision and accuracy of the CBA assay shows low coefficient of variation (6.3-11.1%) with a lower limit of detection 0.2% (linearity 1-530%).

Suggested Reading

1. Favaloro EJ. Von Willebrand factor collagen-binding (activity) assay in the diagnosis of von Willebrand disease: a 15-year journey. Seminar Thromb Hemost. 2002;28:191-202.

2. Nichols WL et al. The diagnosis, evaluation, and management of von Willebrand disease. U.S. Department of Health and Human Services. NIH Publication No. 08-5832, December 2007.

3. Castaman G, Federici AB, Rodeghiero F, Mannucci PM. Von Willebrand disease in the year 2003: toward the complete identification of gene defects for correct diagnosis and treatment. Haematologica. 2003;Jan;88(1):94-108.

4. Kalla A, Talpsep T. The von Willebrand factor collagen binding activity assay: clinical application. An Hematol. 2001;80:466-471.

5. Favaloro EJ. Toward a new paradigm for the identification and functional characterization of Von Willebrand disease. Seminar Thromb Hemost. 2009;35:60-75.

Clinical Indications

This test may be useful in the evaluation of patients with intravasuclar hemolysis, unexplained hemolysis, thrombosis with unusual features, or bone marrow failure.

Interpretation

Results are reported as:

• Negative
• Low-level PNH clone positive (.01 – <1%) with percentage
• PNH clone positive (≥1%) with percentage

Limitations

Results of PNH flow cytometry studies must be interpreted in the context of the clinical, laboratory, and histologic findings.

Blood not collected in a K₂EDTA tube (or one which has been improperly stored and handled prior to receipt) cannot be processed.

Blood stability limit for PNH testing is 24 hours after the stated draw time. Clinical significance of results on specimens 24-48 hours old should be evaluated in the context of other clinical and laboratory findings.

Blood older than 48 hours from draw time cannot be analyzed.

Methodology

High sensitivity flow cytometry for PNH is performed in accordance with Clinical Cytometry Society recommendations for high sensitivity flow cytometry testing.¹

Cells are stained directly with FITC, PE, PE/Cy7, PerCP/Cy5.5, APC, and APC/Cy7-labeled monoclonal antibodies to detect antigens of interest. Antibodies used include CD15, CD24, CD33, CD45, CD59, and glycophorin A. Additionally, FLAER is employed.

For erythrocytes, antibodies to glycophorin A are used to specifically gate red cells, and PNH clones are identified by lack of CD59 expression. PNH erythrocyte clones are divided into those with partial loss of CD59 (PNH Type II Cells) or complete loss of CD59 (PNH Type III Cells).

For granulocytes, CD15 and CD33 are used to specifically gate granulocytes. PNH-type granulocytes are then identified by lack of expression of CD24 and lack of reactivity to FLAER.

References

1. Borowitz MJ, Craig FE, DiGiuseppe JA et al. Guidelines for the Diagnosis and Monitoring of Paroxysmal Nocturnal Hemoglobinuria and Related Disorders by Flow Cytometry. Cytometry B Clin Cytom. 2010; 78B:211-230.

2. Sutherland DR, Kuek N, Davidson J et al. Diagnosing PNH with FLAER and Multiparameter Flow Cytometry. Cytometry B Clin Cytom. 2007; 72B: 167-177.

Clinical Indications

Detection and differentiation of M. tuberculosis from NTM on smear-positive specimens.

Culture for Mycobacterium spp. should be performed on all specimens ordered for acid-fast bacilli because of the possibility of dual mycobacterial infections and to have the isolate available for susceptibility testing if appropriate.

Interpretation

Results are reported qualitatively as positive or negative for M. tuberculosis, and positive or negative for NTM.

Limitations

This assay, as well as commercially-available assays, is insensitive when smear-negative specimens are tested.

This assay has suboptimal sensitivity for some of the rapidly growing Mycobacterium species and M. xenopi.

Methodology

The LightCycler FastStart DNA Master Hybridization Probe Kit (Roche) is used in conjunction with broad-range mycobacterial PCR primers and specially designed FRET hybridization
probes. Rapid-cycle PCR and post-amplification melt curve analysis are performed in the LightCycler system.

References

1. Shrestha NK, Tuohy MJ, Hall GS, Reischl U, Gordon SM, Procop GW. Detection and Differentiation of Mycobacterium tuberculosis and nontuberculous mycobacterial isolates by real-time PCR. J Clin Microbiol. 2003;41:5121-6.

Clinical Indications

There are two major reasons to detect occult blood in the stool: as a screen for colorectal cancer or to detect upper or lower GI bleeding. In the outpatient settings, an immunochemical-based assay (iFOBT or FIT) is used to detect fecal occult blood for colorectal cancer screenings; the three-part guaiac-based fecal occult blood test will no longer be available for screening.

• The single guaiac card (SENSA) will continue to be used for the detection of bleeding (upper or lower GI bleeding).
• The iFOBT (FIT) cannot be used for detection of upper GI bleeding and should only be used as a colon cancer screen test.
• The HemaPrompt card (a guaiac-based POCT assay) was introduced in October 2009 for use as a point-of-care test for detection of upper and lower GI bleeding.
  • It can be used in the Emergency Department and a few other clinical areas that have been granted POCT testing privileges.

If colorectal cancer screening is the intended use of the occult blood test, the iFOBT is the preferred method because it is the more-sensitive screen, and only a single sample collection is required.

One of the main reasons for the change to iFOBT for colorectal cancer screening is that the guaiac-based tests lack the sensitivity and specificity seen with the iFOBT assays. In an early study of iFOBT assays, specimens obtained from 107 colorectal cancer subjects showed that the iFOB test had a 97% sensitivity for detection of colorectal cancer, as compared to a very-sensitive guaiac-based test (Hemoccult Sensa) in which the sensitivity was 94%. The iFOBT also demonstrated greater sensitivity (76%) in detecting large adenomas as compared with guaiac-based tests, in which the sensitivity was 42%. The specificity of the iFOBT was 97.8%, as compared to 96.1% for the gFOB, when 1,355 screening tests were performed. The authors concluded that the iFOBT provided the best combination of specificity and sensitivity.⁵ In a more recent study of performance characteristics for detecting cancer, the sensitivity of the iFOBT test was 81.8% vs. 64.3% with gFOB test.

Specificity for iFOBT was 96.9% and 97.3%, respectively, for detecting cancer and adenomas versus 90% and 90.6% with gFOB. For the detection of large polyps, the sensitivity of the gFOB was actually higher than that with iFOBT in this study.⁶ In a recent study out of Seoul, Korea, a population of average-risk individuals (770 patients from four centers) undergoing colorectal cancer screening were assayed for occult blood comparing a gFOB to an iFOB. The iFOBT provided a higher sensitivity for detecting cancer and advanced colorectal neoplasia than the gFOB and had an acceptable specificity that could significantly reduce the need for colonoscopic evaluation of the screened population.⁷ An editorial in the same issue of the journal from Seoul suggested that the data supported an effort to increase the use of iFOBT assays in the U.S. and publishing of studies in average-risk individuals here as well.⁸

Secondly, various foods and exogenous substances can yield false-positive guaiac-based FOB test results. Vitamin C in excess of 250 mg/day from all sources (dietary and supplemental) can oxidize guaiac. False-positive guaiac-based test results can also occur with excess dietary red meat, such as beef, lamb, processed meat, liver, or plant peroxidases contained in raw fruits and vegetables, especially radishes, turnips, horseradish, cantaloupes, and other melons. Such foods should be avoided for 72 hours prior to testing. GI bleeding can be induced by alcohol, and also has well-known iatrogenic causes, such as steroids and NSAIDS.⁹

The iFOBT assays detect human globin, a protein that along with heme constitutes human hemoglobin. It is more specific for human blood as compared to the guaiac-based tests, and is not subject to the false-negative results seen in the guaiac-based tests in the presence of high dose vitamin C supplements. It is important to remember that the iFOBT assays are specific to bleeding in the lower GI tract.

Thirdly, because of the increased sensitivity of these assays, only one sample is usually required for screening, as compared to the three samples needed when guaiac-based tests are used. The ease of use of these screening assays should enhance patient compliance.

Interpretation

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

Limitations

Patients with the following conditions should not be tested due to a potential for false positive results:

• Bleeding hemorrhoids
• Menstrual bleeding
• Constipation bleeding
• Urinary bleeding

Certain medications, such as aspirin and non-steroidal anti-inflammatory drugs, may cause gastrointestinal irritation and subsequent bleeding in some patients, which may cause false positive results.

Contamination of the sample with urine or toilet water also may cause erroneous results.

The OC-Sensor Diana iFOBT should not be used for testing urine, gastric or other body fluids.

Because iFOB (FIT) tests are dependent on the intact antigenic structure of heme molecules, its use is limited to screening for FOB that is not gastric or upper GI in origin.

Bulk stool samples should not be sent to the lab for occult blood testing, as hemoglobin present in stool begins to degrade within hours of passage.

Methodology

The OC-Sensor Diana iFOB test is an immunoassay-based test that uses rabbit polyclonal antibodies to detect hemoglobin in stool. The test is a turbidimetric latex agglutination test. Hemoglobin present in the patient sample will combine with latex-coated antibody to cause a change in absorbance. A light beam is passed through the reaction cells and measures changes in the intensity of light beam. Testing is performed on an automated analyzer and qualitative results are generated.

Patients should be provided with a collection kit, which is composed of a labeled collection vial, instructions on how to collect the stool sample and inoculate the vial, and an envelope into which the vial can mailed to the laboratories for testing.

Testing is performed on a daily basis, Monday through Friday

References

1. Levin B, Lieberman DA, McFarland B et al. Screening and Surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the U.S. Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. Ca Cancer J Clin. 2008;58:130-60.

2. Smith RA, Cokkinides V, Eyre HJ. Cancer screening in the U.S., 2007: a review of current guidelines, practices, and prospects. CA Cancer J Clin. 2007;57:90-104.

3. Rex DK et al. American College of Gastroenterology Guidelines for Colorectal Cancer Screening 2008. The Am J Gastroenterol. 2009;104:739-50.

4. Rockey, DC. Occult gastrointestinal bleeding. N Engl J Med. 1999;341:38-46.

5. St. John DJ, Young GP, Alexeyeff MA et al. Evaluation of new occult blood tests for detection of colorectal neoplasia. Gastroenterology. 1993;104:1861-8.

6. Sakoda LC, Levin TR et al. Screening for colorectal neoplasms with new fecal occult blood tests: update on performance characteristics. J Natl Cancer Institute. 2007;99:1462-70.

7. Park D, Ryu S, Kim YH et al. Comparison of guaiac-based quantitative immunochemical fecal occult blood testing in a population at average risk undergoing colorectal cancer screening. Am J Gastroenterol. 2010;105:2017-25.

8. Allison JE. Editorial: FIT: a valuable but underutilized screening test for colorectal cancer – it’s time to change. Am J Gastroenterol. 2010;105:1026-8.

9. Bakerman, S. ABC’s of interpretive laboratory data. Fourth Edition. Interpretive Laboratory Data Inc. Scottsdale, AZ. 2002.