Antiphospholipid Antibodies:

Hypercoagulability in renal transplant recipients. Identifying patients at risk of renal allograft thrombosis and evaluating strategies for prevention

Renal transplantation improves survival and quality of life for patients with end-stage renal disease (ESRD). Improvements in immunosuppressive therapy have reduced early allograft loss due to acute rejection to very low levels. Early allograft loss, due to acute thrombotic complications, remains a constant and proportionally increasing complication of renal transplantation. Identifying risk factor(s) for thrombosis amenable to preventive strategies has been elusive. Epidemiological studies have attempted to define risk in terms of modifiable (drugs, dialysis modality, surgical procedure) and non-modifiable (age, diabetes mellitus, vascular anomalies) factors, or identify changes in coagulation or fibrinolysis promoting a more thrombotic state. Most recently the evolution of thrombophilia research has established the potential for inherited hypercoagulability to predispose to acute allograft thrombosis. Inheritance of the factor V Leiden (FVL), prothrombin G20210A mutation, or the presence of antiphospholipid antibodies (APA) may increase the risk of renal allograft thrombosis approximately 3-fold in selected patients. Patients with ESRD due to systemic lupus erythematosus (SLE) appear at particularly high risk of thrombosis, especially if they have either APA or detectable beta(2)-glycoprotein-1. Data for other hypercoagulable states such as hyperhomocystinemia or the C677T polymorphism of the methylenetetrahydrofolate reductase gene are deficient. Patients with APA, FVL, or prothrombin G20210A mutation also appear to have greater graft loss due to vascular rejection, possibly reflecting immunological injury upon the vascular wall exacerbated or induced by the prothrombotic state. While substantial in vitro data suggest cyclosporine is prothrombotic, an independent clinical association with allograft thrombosis is unproven. Interventions to reduce thrombotic risk including heparin, warfarin, and aspirin have been evaluated in both selected high-risk groups (heparin and warfarin) and unselected populations (heparin and aspirin). In unselected patients at low clinical risk, aspirin (75-150 mg/day) with or without a short period of unfractionated heparin (5000U twice a day for 5 days) appears to reduce the risk of renal allograft thrombosis significantly with a low risk of bleeding, especially when compared with low molecular weight heparins which risk accumulation in renal failure. In high-risk groups (identified thrombophilic risk factor, previous thrombosis, or SLE) longer period of heparin, with or without aspirin and maintenance with warfarin, should be considered. Re-transplantation following graft loss due to vascular thrombosis can be undertaken with a low risk of recurrence. Further prospective studies evaluating both putative risk factors and intervention strategies are required to determine whether routine clinical screening for thrombophilic factors is justified.

Immunologic and serologic testing in patients with Ménière's disease

OBJECTIVE

To establish the value of immunologic and serologic testing in patients with Ménière's disease.

STUDY DESIGN

Prospective cohort.

SETTING

University-based, tertiary care balance center.

INTERVENTION

Patients with active unilateral or bilateral Ménière's disease underwent testing, including antinuclear antibodies, anti-DNA antibodies, rheumatoid factor, complement levels, anti-Sjögren syndrome A and B antibodies, sedimentation rate, antiphospholipid antibodies, Western blot for anticochlear antibodies (anti-heat shock protein 70), microhemagglutination test for Treponema pallidum, and Lyme titers.

OUTCOME MEASURES

Results of laboratory tests.

RESULTS

In patients with unilateral Ménière's disease (n = 40), 27% demonstrated elevated antiphospholipid antibody titers (population norm, 6-9%). The majority of these patients manifested negative assays on the other tests listed above. In patients with bilateral Ménière's disease (n = 18), elevations in antinuclear antibody titers (38%) were the most notable finding. As part of a broader study of patients with progressive hearing loss, four patients with positive syphilis titers were identified; however, none of these patients complained of vertigo.

CONCLUSION

In general, the results of this study do not support the hypothesis that immune or infectious pathologies are involved in the pathogenesis of unilateral Ménière's disease. In particular, Lyme disease does not seem to cause labyrinthine disease. However, the potential role of the thrombogenic antiphospholipid antibodies must be further investigated. Patients with bilateral Ménière's disease may be more likely to have a systemic autoimmune process.

Primary anti-phospholipid antibody syndrome (APS): current concepts

Primary anti-phospholipid syndrome (APS) is a thrombophilic state characterized by recurrent arterial and venous thrombosis, recurrent pregnancy loss, and the presence of circulating anti-phospholipid antibodies that may be responsible for thrombophilia and pregnancy morbidity. Ophthalmologic features are present in 15-88% of the patients with primary APS, thus ophthalmologists are one of the first physicians to whom the patient will present. An accurate diagnosis may save the patient from recurrent, potentially life-threatening thrombosis. In the U.S.A., an estimated 35,000 new cases of APS-related venous thrombosis occur each year in a population that is several decades younger than the patient population typically affected by thrombosis. Clinical features, such as chorea, transverse myelitis, cardiac valvular lesions, and accelerated atherosclerosis, are hypothesized to be due to a direct tissue-antibody interaction and cannot be explained purely by thrombosis. The use of recently proposed, well-defined diagnostic criteria, and better standardization of laboratory assays for the anti-phospholipid antibodies should help enable epidemiological surveys to establish the prevalence of these antibodies in patients with thrombosis and in the general population. Diagnosis of APS should be considered in all patients with recurrent systemic or ocular thrombosis in the absence of known risk factors. Several well-designed prospective studies show an increased risk of thrombosis in the presence of medium to high antibody level. With ocular involvement in as many as 88% of APS patients, an ophthalmic assessment should be an integral part of the clinical work-up of any patient with suspected or confirmed APS. The presence of isolated ocular thrombophilia with persistently elevated anti-phospholipid antibodies or lupus coagulant should confirm the diagnosis of APS. Management of these patients must be a multi-disciplinary effort with either a rheumatologist or a hematologist having the overall responsibility for coordinating treatment and monitoring the patient's immune status and anticoagulation. Treatment of isolated ocular thrombophilia in the presence of moderate to high titers of antiphospholipid antibodies should be on the same principles as patients with APS to prevent recurrent ocular or cerebral thrombosis.

Clinical utilization of the international normalized ratio (INR)

The prothrombin time (PT) is one of the most important laboratory tests to determine the functionality of the blood coagulation system. It is used in patient care to diagnose diseases of coagulation, assess the risk of bleeding in patients undergoing operative procedures, monitor patients being treated with oral anticoagulant (coumadin) therapy, and evaluate liver function. The PT is performed by measuring the clotting time of platelet-poor plasma after the addition of calcium and thromboplastin, a combination of tissue factor and phospholipid. Intra- and interlaboratory variation in the PT was a significant problem for clinical laboratories in the past, when crude extracts of rabbit brain or human placenta were the only source of thromboplastin. The international normalized ratio (INR), developed by the World Health Organization in the early 1980s, is designed to eliminate problems in oral anticoagulant therapy caused by variability in the sensitivity of different commercial sources and different lots of thromboplastin to blood coagulation factor VII. The INR is used worldwide by most laboratories performing oral anticoagulation monitoring, and is routinely incorporated into dosage planning for patients receiving warfarin. Although the recent availability of sensitive PT reagents prepared from recombinant human tissue factor (rHTF) and synthetic phospholipids eliminated many of the earlier problems associated with the use of crude thromboplastin preparations, local instrument variability in the INR still remains a problem. Presently, the use of plasma calibrants seems the best solution to this problem. Standardizing the point-of-care instruments for INR monitoring is another dilemma faced by the industry. Ultimately, new generations of anticoagulant drugs may eliminate the need for laboratory monitoring of anticoagulant therapy.

Renal allograft thrombosis: can thrombophilia explain the inexplicable?

Renal allograft thrombosis remains a preventable cause of early allograft thrombosis. It should not be considered simply an unpredictable and poorly understood consequence of surgery. Extrapolated data from the general population and early data from renal patients supports the concept that the interplay of non-inherited hypercoagulability of renal disease with inherited thrombophilia, and the altered environmental milieu of transplantation predisposes to thrombosis (summarized in Figure 2). We should not accept the inevitability of a constant attrition of grafts to thrombosis and need to continue to identify risk factors and confirm appropriate screening and interventions for its prevention, almost certainly requiring collaborative multicentre trials. In the future, just as we now expand the specificity of HLA gene typing with molecular biology, genotyping for recognized thrombophilia genes in patients at risk will expand our ability to recognize and prevent thrombosis with targeted interventions drawn from the increasing array of anticoagulants now available. The contribution of thrombophilia to non-immune mechanisms of chronic allograft loss is also a potentially important but neglected area of research.

Significance of elevated IgG anticardiolipin antibody levels in patients with Budd-Chiari syndrome

OBJECTIVES

Budd-Chiari syndrome (BCS) is characterized by hepatic venous outflow obstruction. Though hypercoagulable states are implicated in the causation of BCS, the etiology remains unknown in most cases. Presence of anticardiolipin antibodies (aCL) is a known cause of hypercoagulable state. We therefore studied the frequency of IgG aCL in BCS.

METHODS

Sera were obtained from 19 patients with BCS, 50 healthy controls, 18 age- and gender-matched patients with cirrhosis, and 15 patients with acute viral hepatitis. IgG aCL levels were measured using a solid-phase enzyme immunoassay. Values exceeding mean + 2 SD of healthy controls were taken as abnormal.

RESULTS

Mean +/- SD IgG aCL levels (GPL units) in the four groups were: healthy controls, 6.3 +/- 4.4; BCS, 13.8 +/- 13.3 (p < 0.05, compared with healthy controls); cirrhosis, 15.1 +/- 14.9 (p < 0.05, compared with healthy controls and p = ns, compared with BCS patients); and acute viral hepatitis, 5.0 +/- 2.5 (p = ns, compared with healthy controls). The levels in BCS and cirrhosis patients were similar (p = ns). The number of patients with elevated aCL was: healthy controls, 3/50; BCS, 6/19; cirrhosis, 7/18; and acute viral hepatitis, 0/15. The number of patients with elevated IgG aCL was significantly higher among patients with BCS and cirrhosis, compared with controls (p = 0.03 and p = 0.002, respectively).

CONCLUSIONS

Patients with BCS had higher IgG aCL levels than healthy controls. However, as aCL levels were also elevated in patients with cirrhosis, the pathogenetic role of IgG aCL in the causation of BCS is doubtful.