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Synonyms
- Neutralization, Hexagonal Phase Phospholipid
Special Instructions
If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions.
Expected Turnaround Time
2 - 3 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Related Information
Related Documents
For more information, please view the literature below.
Procedures for Hemostasis and Thrombosis: A Clinical Test Compendium
Specimen Requirements
Specimen
Plasma, frozen
Volume
1 mL
Container
Blue-top (sodium citrate) tube
Collection
Citrated plasma samples should be collected by double centrifugation. Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.2,3 The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples, except when using a winged blood collection device (ie, "butterfly"), in which case a discard tube should be used.4,5 When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternate anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes. Centrifuge for 10 minutes and carefully remove 2/3 of the plasma using a plastic transfer pipette, being careful not to disturb the cells. Deliver to a plastic transport tube, cap, and recentrifuge for 10 minutes. Use a second plastic pipette to remove the plasma, staying clear of the platelets at the bottom of the tube. Transfer the plasma into a LabCorp PP transpak frozen purple tube with screw cap (LabCorp No. 49482). Freeze immediately and maintain frozen until tested.
Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.
Storage Instructions
Freeze.
Patient Preparation
Ideally, the patient should not be on anticoagulant therapy. Avoid warfarin (Coumadin®) therapy for two weeks prior to the test and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing. Do not draw from an arm with a heparin lock or heparinized catheter.
Causes for Rejection
Severe hemolysis; improper labeling; clotted specimen; specimen diluted with IV fluids; samples thawed in transit; improper sample type; sample out of stability
Test Details
Use
This test system is designed for the qualitative detection of lupus anticoagulants in plasma.6
Limitations
Anticoagulant therapy may cause false-positive results. Plasma heparin levels >2 IU/mL may interfere with this test.7 Platelets are a rich source of phospholipid that can neutralize LA. Improper preparation of the platelet-poor plasma at collection reduces the sensitivity of this assay for LA. This test is subject to false-positive cross-reactivity with factor VIII inhibitors.8
Methodology
Clotting time using an activated partial thromboplastin time (aPTT) reagent is determined both in the presence and in the absence of HPP. The assay is considered to be positive for lupus anticoagulant when addition of HPP reduces the aPTT by more than the laboratory defined cutoff.
Reference Interval
Patients with a prolonged aPTT or lupus sensitive aPTT screening test:
• Reduction of the aPTT result by more than a laboratory-determined cutoff (test result that is elevated) as the result of adding hexagonal phase phospholipid (HPP) is consistent with the presence of a phospholipid-dependent inhibitor (lupus anticoagulant).
• Failure of the HPP to reduce the aPTT result (test result that falls in the normal reference interval) can be interpreted as a possible indication of the presence of one or more specific factor inhibitors.
Additional Information
Lupus anticoagulants are nonspecific inhibitors of phospholipid-dependent in vitro coagulation tests.6 The HPP assay takes advantage of the fact that many LA antibodies specifically recognize the HPP phospholipid configuration as an antigenic epitope. Addition of HPP to the reaction mixture serves to neutralize the inhibitory effect caused by LA antibodies and does not neutralize most factor-specific antibodies.9,10 The assay design includes several features that serve to improve the clinical utility of the test.7 The aPTT reagent used is diluted to reduce its phospholipid concentration and increase sensitivity to LA. The addition of normal plasma to the test system serves to correct for any clotting time prolongation caused by factor deficiencies in the patient plasma. This improves the specificity for LA by making the test relatively insensitive to factor deficiency. The assay reagent also contains a heparin neutralizer, which makes the test system insensitive to heparin levels up to 2 IU/mL. This assay can be used to detect lupus anticoagulants in patients receiving warfarin therapy.
Footnotes
1. Adcock DM, Kressin DC, Marlar RA. Effect of 3.2% vs 3.8% sodium citrate concentration on routine coagulation testing. Am J Clin Pathol. 1997Jan;107(1):105-110.8980376
2. Reneke J, Etzell J, Leslie S, Ng VL, Gottfried EL. Prolonged prothrombin time and activated partial thromboplastin time due to underfilled specimen tubes with 109 mmol/L (3.2%) citrate anticoagulant. Am J Clin Pathol. 1998 Jun;109(6):754-757.9620035
3. National Committee for Clinical Laboratory Standardization. Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline. 5th ed. Villanova, Pa: NCCLS; 2008. Document H21-A5:28(5).
4. Gottfried EL, Adachi MM. Prothrombin time and activated partial thromboplastin time can be performed on the first tube. Am J Clin Pathol. 1997 Jun;107(6):681-683.9169665
5. McGlasson DL, More L, Best HA, Norris WL, Doe RH, Ray H. Drawing specimens for coagulation testing: Is a second tube necessary? Clin Lab Sci. 1999 May-Jun;12(3):137-139.10539100
6. Brandt JT, Triplett DA, Alving B, et al. Criteria for the diagnosis of lupus anticoagulants: An update. On behalf of the Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibody of the Scientific and Standardisation Committee of the ISTH. Thromb Haemost. 1995;74(4):1185-1190.8560433
7. CRYOcheck™ Hex LA from Precision BioLogic Information for Use. Rev 04; 12-2020.
8. Brandt JT, Barna LK, Triplett DA. Laboratory identification of lupus anticoagulants: Results of the Second International Workshop for Identification of Lupus Anticoagulants. On behalf of the Subcommittee on Lupus Anticoagulants /Antiphospholipid Antibodies of the ISTH. Thromb Haemost. 1995 Dec;74(6):1597-1603.8772243
9. Rauch J, Tannenbaum M, Janoff AS. Distinguishing plasma lupus anticoagulants from antifactor antibodies using hexagonal (II) phase phospholipids. Thromb Haemost. 1989;62(3):892-896.2512678
10. Triplett DA, Barna LK, Unger GA. A hexagonal (II) phase phospholipid neutralization assay for lupus anticoagulant identification. Thromb Haemost. 1993;70(5):787-793.8128436
References
Adcock DM, Gosselin R. Direct oral anticoagulants (DOACs) in the laboratory: 2015 review. Thromb Res. 2015 Jul;136(1):7-12.25981138
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 117838 | Hexagonal Phase Phospholipid | 3282-1 | 117839 | Hexagonal Phase Phospholipid | sec | 3282-1 |
| Reflex Table for Hexagonal Phase Phospholipid | ||||||
|---|---|---|---|---|---|---|
| Order Code | Order Name | Result Code | Result Name | UofM | Result LOINC | |
| Reflex 1 | 117841 | Comment | 117841 | Comment | 77202-0 | |
| Reflex Table for Hexagonal Phase Phospholipid | ||||||
|---|---|---|---|---|---|---|
| Order Code | Order Name | Result Code | Result Name | UofM | Result LOINC | |
| Reflex 1 | 117800 | Comment | 117800 | Comment | N/A | |
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