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New Treatments for Lupus Anticoagulant



The lupus anticoagulant has been said to be an antiphospholipid antibody. It is a relatively common syndrome, often known as the antiphospholipid syndrome or lupus anticoagulant syndrome. Its diagnosis depends both on clinical and laboratory criteria. For the clinical criteria, rather than bleeding, we are looking here at either arterial or venous thrombosis, and/or morbidity during pregnancy. That is pregnancy losses on a recurrent basis. In terms of laboratory criteria for the syndrome, we diagnose this with an anticardiolipin antibody that usually needs to be of medium or high titer, either in the presence or absence of a lupus anticoagulant. These tests should be repeated and be positive at a second testing at least six weeks distant from the first. Because there appear to be transient positive, especially, anticardiolipin antibodies in normal subjects. The IgG or IgM anticardiolipin antibody testing that we do in the lab usually is a fairly straightforward ELISA assay. But I do want to emphasize that the titer needs to be usually - depending on the normal ranges - 35 or 40 or above to be considered a medium or high titer. So the lower titered ones are of questionable significance, particularly in terms of the lupis anticoagulant.

What are the clinical correlates? Besides the thrombosis that we mentioned, patients may also have thrombocytopenia. They may have other immune problems with autoimmune hemolytic anemia. Many may present - especially women - with livedo reticularis and there can be associated cardiac valve disease and central nervous system syndromes, probably caused by thrombosis. The classification has fallen into the usual primary and secondary, and of course in the primary there is no known underlying disease. In the secondary the most common cause is probably autoimmune disease such as lupus or other autoimmune diseases, rheumatoid arthritis and so on.

The actual diagnosis, in terms of laboratory diagnosis, is made using the anticardiolipin antibodies. Itís an ELISA plate and we now understand that these antibodies are not directed directly against the anionic phospholipids but they are actually directed against a protein called beta 2 glycoprotein 1. Beta 2 glycoprotein 1 is a normally circulating protein at about 200 mcg/ml so there is a lot of it present. When one adds plasma or serum to a plate thatís coated with cardiolipin there will be plenty of beta 2 glycoprotein 1 present which will complex with this cardiolipin in the plate and actually be the binding site for the antibody thatís present in the patientís plasma.

What are the antibodies, the lupus anticoagulants do? They of course, as you know, cause a prolonged clotting time in the test tube. These long clotting times occur in the phospholipid-dependent assays and they will usually correct - or they should correct - with the addition of extra phospholipid and thatís really a criterion for making the diagnosis of lupus anticoagulant. What are these tests that are going to be prolonged? Well usually, since we screen with an APTT that is one of the tests that will be the first one that we note as being prolonged. Generally if the anticoagulant is of sufficient titer it will not correct with a mixing study with normal plasma. So if you take normal plasma 1:1 with a patient, the APTT will still be prolonged. There is a specific test called the stay-clot (?) test as well as perhaps some others that use the APTT system.

Now itís very very important that you collect the blood for this test in the proper way. The problem occurs - and you can get false negative tests - if you have platelet fragments which can remain up in the supernaten plasma after you separate red cells and white cells and platelets from the plasma. So most laboratories would recommend either extremely extensive hard spins, or better yet usually what we do is filter the plasma to remove any of the fragments which would otherwise bind or soak up this anticoagulant and remove it from the test and cause the test to be falsely normal. So it is important how you collect the plasma and you should remember that you cannot freeze the plasma.

What about the pathophysiology? We just said that it prolongs the clotting time, but in the patient they get thromboses. It doesnít make a lot of sense. Now there are several different mechanisms and one of the more recent mechanisms for causing thrombosis in patients that has been proposed by Rand et al is probably at least going to be present in many of these lupus anticoagulant patients who have clots. That has to do with another substance called annexin 5 which normally is at the surface of a phospholipid membrane, platelets or endothelial cells, where clotting is going to take place. You obviously need a site. You need a phospholipid site for normal coagulation. Usually these sites, these

Now if you specifically have relatively high titers of antibodies against prothrombin rather than just displacing annexin 5 and allowing clotting to take place at the membrane, you can also cause a bleeding problem. In these patients the mechanism by which that occurs appears to be twofold. One, you can interfere with the assembly of the so-called prothrombinase complex, which is the activated factors that are going to activate prothrombin and thrombin; the 10A5 phospholipid calcium complex. That is interfered with by antibodies to prothrombin, certain antibodies to prothrombin. The second way is what I mentioned earlier and you can actually get hypoprothrombinemia because the antigen

Other mechanisms that have been proposed and certainly have been described in individual patients, include; the antibodies actually somehow inhibiting the activation of protein C and inhibiting prostacyclin generation, and also activating platelets. There have been some studies looking at the tissue factor present on monocytes and other cell surfaces which seem to be increased also in the presence of lupus anticoagulants. So there may be a number of different mechanisms that are operative that lead to clotting in this syndrome.

What about treatment? Well, we are looking at a thrombotic disease so we need anticoagulation, and as you would expect for acute thrombosis. You treat as you would any patient, usually with heparin followed by Coumadin. This anticoagulation should be continued for at least six months and it may be very important to continue it for a longer time depending on the status of the patient. If the lupus anticoagulant and underlying syndrome that perhaps the patient has disappears, you may not need longer anticoagulation. However, you may because look at this

Now during pregnancy when this certainly occurs as well, what should one be doing? Patients who have recurrent pregnancy losses should, during their next pregnancy, receive low molecular weight heparin and again, oftentimes, low dose aspirin is added. The increase in fetal survival is about 50-80%, so this has been fairly effective treatment in these patients. I should add that there has been some debate about the level of Coumadin, Coumadin-ization that should be maintained in these patients. There is evidence in some peopleís hands that they feel that higher dose or higher doses sufficient to cause the INR to be 3.5 or above is important. I think the answer isnít entirely known and one has to

Factor VIII inhibitors. They are rare in the population except for hemophiliacs. Itís actually more like one in a million. So we are looking at a very unusual illness, but the mortality rate can be quite high in this acquired anticoagulant so one should definitely be aware of it. These can be either a spontaneous antibody, at least we donít know what has elicited the antibody, or they can be associated sometimes with other autoimmune diseases like lupus, rheumatoid. They do occur in pregnant women and peripartum. Interestingly enough they do not always recur with subsequent pregnancies so one cannot predict whether it will or not. And then with allergic reactions one may see this occur. Penicillin has been a particularly big offender. In the spontaneous patients I guess the classic presentation often is in a patient above 55, 60 years of age

Now, third, we are going to talk a little bit about von Willebrand, acquired von Willebrand disease. It often may occur because of an antibody against von Willebrand factor, much like the other syndromes that we have talked about. However there can be other causes for acquired von Willebrand disease. That can occur when there is proteolysis of von Willebrand factor through shear mechanisms; perhaps cardiac disease, valve disease. Increased shear in smaller vessels as well. Binding of the von Willebrand factor to tumor cells and its clearance has been described. Decreased synthesis of von Willebrand factor from perhaps severe hypothyroidism, and then there have been some drug-associated cases where we donít really know the mechanism well. The diseases that these occur in, the antibodies of course occur more often in lymphoproliferative

How do we make the diagnosis? Well, we look at and get a good history from the patient to try and find out if theyíve had any exposure during recent surgery, or with any other reason to have had topical thrombin. One then tries to recheck a thrombin time with human thrombin rather than bovine thrombin, and if this is directed simply against the bovine thrombin itís clinically irrelevant. Itís not important and no treatment will be required. Thatís the usual case. Occasionally, because these topical thrombin preparations are not just thrombin - they contain other clotting factors, including factor V - one may get antibodies also directed against factor V, bovine factor V, which often and more often will cross-react with human factor V leading to a true circulating anticoagulant. So the antibody can be formed, from these preparations, against bovine factor V that does cross-react. In this case one will see in the patient - since the antibody is in the final common pathway - an elevation of both the APTT and the pro time and no correction, since itís an antibody, with a 1:1 mix. If one looks in a specific factor V assay one will

A caveat here, just to comment; some of the newer coagulation instruments have of course factor assays on them and they provide often, and want you to use their own substrate deficient plasmas for these tests, such as factor V or factor II, which one might look at in some of these cases. The antibodies are directed primarily against the bovine reagents so if one uses human factor V deficient substrate to measure factor V it will be usually less of a titer than one would see against the bovine factor V. In some of the cases that we have seen recently we have realized that the substrate plasma that weíve used has been artificially depleted rather than obtained from a factor V or II deficient patient. Those depletions require some repletion with factors by the manufacturing company. They will often use bovine products to replete the factors that theyíve removed that they donít want removed from the plasma. You are trying to just get one factor thatís deficient, if you are measuring that one factor. One needs to be very careful. Actually one of our factor II or prothrombin assays uses a substrate that has plasma that has been

The diagnosis is, as we said before, a long PTT and pro time not correcting, a low factor V on specific assay. Again, platelets can often be quite effective since they are protected from the circulating antibody.

Heparin-like anticoagulants, another acquired problem thatís not common but can be quite a puzzle. The mechanism of these heparin-like anticoagulants is that they of course will act very much like heparin. The heparin sulfate combined antithrombin 3 and inhibit all of the activated coagulation factors that heparin AT3 does. A diagnosis may be suspected when you see a prolonged APTT and thrombin time usually that does not correct. You may see some correction with protamine but it often is not as good as with heparin, since the protamine does not bind as tightly to the heparin sulfate. The treatment in these patients, if they are bleeding, potentially protamine sulfate can be useful. Often these patients are not bleeding but you will get a consult because there is an abnormal coagulation test.

Acquired dysfibrinogens, we see them associated with hepatic disease. It can be cirrhosis, chronic active hepatitis, sometimes hepatomas or massive hepatic metastases. Why dysfibrinogens should cause bleeding; they can actually interfere with the normal fibrin monomer polymerization since they are abnormal and wonít form a firm clot. Usually that can be reflected in the thrombin time, also the reptilase time and you will see a discrepancy if you measure this thrombin time or the activity, versus the total amount of fibrinogen by an immunologic or

The last four we are going to talk about are antibodies that occur or mechanisms for decreasing factor X and XI and XII and XIII. Basically these are very very rare. There has been a very famous case of low factor X thatís been associated with amyloidosis and it was beautifully demonstrated, actually, that the factor X was taken out of the circulation by binding to the amyloid protein. In cases where there are actually antibodies rather than this amyloid mechanism, one sees in the testing what would be expected with an antibody. Again here, since it is factor X, will affect both the extrinsic and intrinsic pathways. Youíll see a prolongation of both the APTT and pro time not correcting, and again if

Inhibitors of factor XI, again very uncommon. They can cause problems by several mechanisms. They may bind to the active site or they can block absorption of factor XI, which is important for the rest of the coagulation to occur. Diagnosis again, in this case itís just the X intrinsic