Lupus Anticoagulant Testing

Anfal Helu asked: I have a question regarding the screening and confirmatory testing for the lupus anticoagulant (LA). Recently, a young female pt was clotting everywhere after a hospital visit for a status epilepticus attack during which she was intubated and placed on mechanical ventilation. She had 2 pulmonary emboli, 2 MI, ischemic colitis, renal necrosis, as well as newly discovered adrenal and pulmonay nodules.

Testing was done to confirm the reason for her thrombotic state which revealed hexagonal phase staclot LA positive, and staclot LA delta prolonged. The DRVVT ratio was normal as well as DRVVT LA– AB. The  PT and PTT were normal, and the beta glycoprotein and cardiolipin were normal. The pathology report states there is a positive LA.

I am a new resident and want to interpret the confirmatory testing the pathologist used here. How was he able to confirm a positive result when everything was negative, such as all antibodies and the PT/PTT/DRVVT except for the hexagonal phase and delta staclot? This patient has been in the hospital and on DVT therapy. There was no DVT found for the clots and no reason for thrombosis.

Prior testing was negative for ANA, ESR, CRP, and all common antibodies associated with auto-immune diseases, as well as anti-cardiolipin which is most common for anti-phospholipids. She had testing done months prior because of a rash that kept appearing on her face and a “change in character.”

My main question is; Is the hexagonal phase that much superior in its confirmatory results in comparison to other tests done? It seems as though he based it only on that and the delta LA.

Sorry, I have a lot of questions because these are all new tests to me and it did not make sense. I have found out same patient came in again because of loss of sensation, severe pruritus, and stinging sensation yet no rash in the temporal side of her head, and woke up to patches of hair loss. we would think discoid but no scales or skin lesions at all, also I have not heard of discoid lupus causing these symptoms. This case is all very interesting to me. I would appreciate any input. Thank you.

Hello, Anfal Helu, I shared your question with Ali Sadeghi-Khomami, PhD, lead scientist at Precision BioLogic, Inc. and developer of PBI’s Hex LA. Here is his response:

I am not a clinician, but I have seen case reports of antiphospholipid syndrome (APS) with various manifestations from hearing loss to mood swings, skin disorders livedo reticularis, etc.

From the lab diagnosis perspective, the pathologist’s report is correct. According to ISTH guidelines, two LA assays based on different principles need to be done (Hexagonal APTT, dRVVT in this case) and if one of them is positive, the sample should be reported LA-positive (see below). This is due to the heterogeneity of antibodies involved and these antibodies could target different protein-phospholipid targets. It is necessary to repeat lab testing after 12 weeks to differentiate the incident from transient LA. Sampling from a patient in the acute phase doesn’t produce an accurate result (due to anticoagulant drug interference or imbalance coagulation factors). PT and PTT (APTT, aPTT) reagents used by the lab may not be sensitive to LA. We need the name of the reagents, normal range, and patient result to assist further (if we could).

What kind of antibody testing has been done in this case? IgG/IgM/IgA aCL and abGPI? What was the lab’s titer and reference interval (RI)? If the lab is equipped with aPT-PS antibody testing, it would be beneficial to run it. Although this antibody test is not on the ISTH guideline yet, it is strongly associated with LA-positive results.

The LA assay result, compared to the anti-phospholipid antibodies (APAs), has the strongest correlation with thrombotic events. However, if no AP antibody could be found in the patient’s sample, there is also a possibility of a false positive Staclot-LA (prone to clinical interferences). Their lab could run Cryocheck Hex LA and check it out. See the attached reference below for details summarized here:

1. Two tests based on different principles
2. dRVVT should be the first test considered.
3. The second test should be a sensitive aPTT (low phospholipids and silica activator.
4. LA should be considered positive if one of the two tests gives a positive result.
   Once a patient has been identified as positive for LA, it is imperative testing be repeated on a second occasion >12 weeks after the initial testing. It is preferable for specimens to be obtained prior to or in the absence of anticoagulant therapy, as this may interfere with the assay. Caution should be exercised in the interpretation of results of tests performed close to a thrombotic event as patients may be treated with full doses of unfractionated heparin and/or vitamin K antagonists. Furthermore, acute phase reactants such as FVIII may be increased during acute events.