Direct oral anticoagulant adsorption and laboratory detection of lupus anticoagulant

Direct oral anticoagulants (DOACs) interfere with many coagulation assays, mostly in lupus anticoagulant (LA) detection, causing false positive and negative results. Despite guidelines recommendations, LA testing may be important during anticoagulation when the clinician has to decide whether to prolong or discontinue the drug.

OBJECTIVES

In this study, the effect of activated charcoal (DOAC-Stop, DS) as a DOAC-adsorbent was investigated on samples from DOACs treated and untreated patients.

BASIC METHODS

165 plasma samples with a LA request were collected in three laboratories: 105 were from patients receiving DOACs and 60 were from nonanticoagulated patients with 30 LA negative and 30 LA positive. All coagulation screening assays and LA assays were evaluated before and after DS treatment.

RESULTS

The adsorption technique reduced DOACs concentration below the Lower Limit of Quantification. For nonanticoagulated patients: no significant difference in ratio results of coagulation screening (prothrombin time, activated partial thromboplastin time and thrombin time) and LA tests were observed before and after addition of DS in LA positive and negative patients. Every LA was correctly classified. For anticoagulated patients: a statistically significant difference was found for coagulation screening assays and LA assays. Final LA conclusions changed after DS addition from positive to negative in 58.9% of patients (more frequently with Rivaroxaban) and from negative to positive in 8% of patients (more frequently with Apixaban).

CONCLUSIONS

Our study suggests that DOAC-Stop can be used in daily laboratory practice to remove DOACs interference for a more accurate assessment of LA that is essential for diagnosis and management of APS patients.

ADAMTS13 Autoantibodies and Burden of Care in Immune Thrombotic Thrombocytopenic purpura: New Evidence and Future Implications

The introduction Caplacizumab in the management of Immune thrombotic thrombocytopenic purpura (iTTP) has raised different questions, considering its cost-efficacy and the optimal immunosuppressive treatment (IST) to associate. A retrospective multicenter collection of 42 first iTTP cases was conducted to identify variables associated with a higher burden of care and necessity of an implemented IST with early Rituximab (RTX) rescue. A significant correlation resulted between ADAMTS13 inhibitors (ADAMTS13inh) at diagnosis with total plasma exchange (PEXtot) and PEX needed to achieve clinical response (PEXtoCR, r = 0.46; r = 0.48), along with age (r = - 0.31; r = -0.35), platelet count (r = -0.30; r = -0.30), LDH (r = 0.44; r = 0.41) and total bilirubin (r = 0.54; r = 0.35). ADAMTS13inh also correlated with number of days of hospitalization (DoH, r = 0.44). A significant difference was observed in terms of median ADAMTS13inh titer at diagnosis in patient treated with RTX rescue and those responding to only steroid treatment. Thus, ADAMTS13inh titer resulted a marker of iTTP burden of care, associated with higher number of PEXtot, PEXtoCR, DoH and higher probability of needing RTX rescue to achieve clinical response and could be a useful tool for management of new iTTP cases and an interesting variable to optimize iTTP cases stratification in future Caplacizumab cost-efficacy analysis.

Antiphospholipid Antibodies and Infection: Non Nova Sed Nove

The clinical significance of antiphospholipid antibodies (aPL) in the context of infections has attracted attention since their first discovery in patients with syphilis. In fact, the recognition of aPL in patients with infections has been described in parallel to the understating of the syndrome. Since the first description of aPL-positive tests in three patients with COVID-19 diagnosed in January 2020 in Wuhan, China, a large number of studies took part in the ongoing debate on SARS-2-Cov 2 induced coagulopathy, and many following reports speculated a potential role for aPL. In order to get further insights on the effective role of detectable aPL in the pro-thrombotic status observed in COVID-19 patients, we performed an observational age-sex controlled study to compare the aPL profile of hospitalized patients with COVID with those observed in a) patients with thrombotic APS and b) patients with cultural/serologically-proved infections. Our data showed positive aPL testing in about half of the patients (53%) with COVID-19 and patients with other viral/bacterial infections (49%). However, aPL profile was different when comparing patients with overt APS and patients with aPL detected in the contest of infections. Caution is therefore required in the interpretation and generalization of the role of aPL s in the management of patients with COVID-19. Before introducing aPL testing as a part of the routine testing in patients with COVID-19, larger well-designed clinical studies are required. While the pro-thrombotic status in patients with COVID-19 is now unquestionable, different mechanisms other than aPL should be further investigated.

Inhibitory anti ADAMTS13 antibodies with a new rapid fully automated CLiA assay

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disorder characterized by severe ADAMTS13 deficiency. The acquired form is associated with autoantibodies directed against ADAMTS13. Both noninhibitory and inhibitory autoantibodies can be detected by ELISA assay, while only inhibitory autoantibodies are detected by Bethesda assay. Due to its short TAT and good performance, chemiluminescence (CliA) ADAMTS13 activity (HemosIL Acustar) has proven to be a good choice in the diagnosis of TTP in emergency settings. Aim of this study was to analyse the performance of the CliA ADAMTS13 activity assay in detecting inhibitory ADAMTS13 antibodies using the Bethesda assay.

METHODS

A method comparison study was performed on 69 stored samples: 11 acute TTPs, 38 TTP follow-ups, 5 TTP relapses, 1 congenital TTP, 10 HUS, 4 suspected TTPs. We retrieved the results of tests previously run in ELISA for both activity and autoantibodies. At the same time, we reran new tests including ELISA and CliA activity, ELISA autoantibodies, and ELISA and CliA Bethesda assays on thawed frozen samples.

RESULTS

Very good correlation was observed between ELISA and CliA activity assay results (r = 0.96) and between archived ELISA and CliA activity results (r = 0.93). Agreement between the anti-ADAMTS13 assays ranged from good (k = 0.63) to very good (k = 0.92).

CONCLUSIONS

CliA and ELISA Bethesda assays showed very good agreement with samples run at the same time using ELISA ADAMTS13-autoantibody assay. Albeit more expensive, the CliA Bethesda assay identified inhibitory anti-ADAMTS13 within almost the same TAT as ELISA, but with better automation and limited operator involvement.

Extended half-life rFIX in major surgery-How to improve clinical practice: An intraindividual comparison

Practical, safe, and effective hemostatic approach to orthopedic surgery using Extended Half-Life factor IX in hemophilia B. By intraindividual comparison, we found a lower FIX consumption, number of infusions, and cost compared to plasma-derived FIX.

A collaborative study by the Working Group on Hemostasis and Thrombosis of the Italian Society of Clinical Biochemistry and Clinical Molecular Biology (SIBioC) on the interference of haemolysis on five routine blood coagulation tests by evaluation of 269 paired haemolysed/non-haemolysed samples

Introduction

Haemolysis is the leading cause of sample rejection in laboratory haemostasis. Most studies focused on artificially haemolysed samples. The aim of this study was a prospective assessment of spontaneous haemolysis on haemostasis tests, by comparing results of haemolysed (H) versus new, non-haemolysed (NH) specimens, collected within 4hrs. As new coagulometers can identify interfering substances, visual assessment of haemolysis was also compared with instrumental haemolysis index and stratified in subclasses.

Materials and methods

Two hundred and sixty nine paired samples were collected and analysed using ACL TOP750-CTS (Instrumentation Laboratory, Bedford, USA), for prothrombin time (PT), activated partial thromboplastin time (aPTT), D-Dimer (DD), fibrinogen (Fib) and antithrombin (AT). Bias between H and NH was calculated and compared with the respective critical difference (CD).

Results

Mean bias was - 0.1 s for PT (P = 0.057), - 1.1 s for aPTT (P < 0.001), 1025 ng/mL for DD (P < 0.001), - 0.04 g/L for Fib (P = 0.258) and 1.4% for AT (P = 0.013). Bias exceeding the CD varied according to the method, with larger differences for aPTT (36.1%) and DD (17.1%) and < 8% for PT, Fib and AT. No correlation emerged between free haemoglobin values and difference in haemostasis tests in H and NH samples for any tests. Moderate/severe haemolysis involved > 95% of samples. The agreement between visual assessment and instrumental evaluation of haemolysis was 0.62.

Conclusion

Spurious haemolysis deeply influences aPTT and DD, and to a lesser extent AT and Fib. Prothrombin time seems only slightly influenced, suggesting that PT can be accepted also in haemolysed samples. Although a good inter-observer correlation of haemolysis evaluation was found, the instrumental assessment of haemolysis seems recommendable.

Reliability of Lupus Anticoagulant and Anti-phosphatidylserine/prothrombin Autoantibodies in Antiphospholipid Syndrome: A Multicenter Study

Background: Is it well-known that one of the major drawbacks of Lupus Anticoagulant (LA) test is their sensitivity to anticoagulant therapy, due to the coagulation based principle. In this study we aimed to assess the reproducibility of LA testing and to evaluate the performance of solid assay phosphatidylserine/prothrombin (aPS/PT) antibodies.

Methods: We included 60 patients that fulfilled the following inclusion criteria: (I) diagnosis of thrombotic antiphospholipid syndrome (APS); (II) patients with thrombosis and (a) inconstant previous LA positivity and/or (b) positivity for antiphospholipid antibodies (aPL) at low-medium titers [defined as levels of anti-β2Glycoprotein-I or anticardiolipin (IgG/IgM) 10–30 GPL/MPL] with no previous evidence of LA positivity. aPL testing was performed blindly in 4 centers undertaking periodic external quality assessment.

Results: The 60 patients enrolled were distributed as follows: 43 (71.7%) with thrombotic APS, 7 (11.7%) with thrombosis and inconstant LA positivity and 10 (16.7%) with low-medium aPL titers. Categorical agreement for LA among the centers ranged from 0.41 to 0.60 (Cohen's kappa coefficient; moderate agreement). The correlation determined at the 4 sites for aPS/PT was strong, both quantitatively (Spearman rho 0.84) and when dichotomized (Cohen's kappa coefficients = 0.81 to 1.0). Discordant (as defined by lack of agreement in ≥3 laboratories) or inconclusive LA results were observed in 27/60 (45%) cases; when limiting the analysis to those receiving vitamin K antagonist (VKA), the level of discordant LA results was as high as 75%(15/20). Conversely, aPS/PT testing showed an overall agreement of 83% (up to 90% in patients receiving VKA), providing an overall increase in test reproducibility of +28% when compared to LA, becoming even more evident (+65%) when analyzing patients on VKA. In patients treated with VKA, we observed a good correlation for aPS/PT IgG testing (Cohen's kappa coefficients = 0.81–1; Spearman rho 0.86).

Conclusion: Despite the progress in the standardization of aPL testing, we observed up to 45% of overall discrepant results for LA, even higher in patients on VKA. The introduction of aPS/PT testing might represent a further diagnostic tool, especially when LA testing is not available or the results are uncertain.

Use of Modified Functional Assays for Activated Protein C Resistance in Patients with Basally Prolonged aPTT

Inherited resistance to activated protein C (APCr) is currently recognized as the most prevalent cause underlying venous thrombophilia, with an estimated prevalence around 20% in thrombotic patients and around 1.8-7% in the general population. A correct laboratory diagnosis of APCr is therefore essential. Two different diagnostic approaches are at present at our disposal: the semi-quantitative plasma test based on the measurement of two aPTTs (in the presence and absence of activated protein C), and the detection of the factor V Arg506 GIn mutation by DNA analysis.

In this study we firstly evaluated sensitivity, specificity and diagnostic efficiency of an aPTT-based plasma clotting test (Chromogenix, Sweden) versus DNA analysis; then, since the APC resistance test is invalidated by a basally prolonged aPTT (i.e. during warfarin and heparin therapy or in patients with clotting factor deficiencies or in the presence of a lupus anticoagulant), patient plasmas were conveniently diluted in factor V deficient plasma in order to correct clotting factor abnormalities. Nevertheless, patients with a LA and an aPTT ratio range 1.8-3.17 were still all misclassified. We obtained correct diagnoses in LA positive patients by preincubating plasmas with a mixture of phospholipids; therefore we decided to perform a double modified clotting test adding a mixture of platelet derived phospholipids to samples previously diluted in factor V deficient plasma. The performance characteristics of this novel method with a different aPTT reagent (Behring, Germany) were also evaluated. With this double modified test all patients were correctly classified as negative or positive for factor V mutation in agreement with DNA analysis, irrespectfully of the basal aPTT value and the aPTT reagent employed. We propose this modified version of the APCr clotting test as an easily reproducible, reliable, very sensitive and specific screening test which possibly reduces the need for DNA analysis.

Carotid Intima-Media Thickness and Anti-Phospholipid Antibodies in Patients with Systemic Lupus Erythematosus

An increase in mortality due to accelerated atherosclerosis has been reported in patients affected with Systemic Lupus Erythematosus (SLE). Anti-phospholipid antibodies (aPA) may play a pathogenetic role in the development of atherosclerosis. We measured carotid intima-media thickness (IMT), as a surrogate parameter of atherosclerosis, by B-mode ultrasound examination in 42 patients affected with SLE (11 men and 31 women) and in 42 healthy age- and sex-matched subjects. Lupus Anticoagulant (LA) (APTT sensitive, silica clotting time, DRVVT), Anti-cardiolipin antibodies (ACA) IgG and IgM, anti-β2glycoprotein 1 (anti-β2GP1) IgG and IgM and anti-prothrombin (anti-PT) IgG and IgM in ELISA (Orgentec Bouty) were also detected. IMT was 0.538±0.128 mm (0.310–0.866 mm) in SLE vs 0.473±0.084 mm in healthy subjects (-p 0.003–). IMT correlated with patients’ age (p<0.005) and with C Reactive Protein (CRP) (p<0.005), but not with years of disease, hypertension, number of anti-hypertensive drugs, total cholesterol, serum creatinine and proteinuria. Sixteen patients (38%) had aPL: 12 LA, 6 ACA IgG, 4 ACA IgM, 4 anti-β2GP1 IgG, 3 anti-β2GP1 IgM, 2 anti-PT IgG and 1 anti-PT IgM. IMT was not statistically correlated with aPA. Positive and negative aPA patients only differed as regards glomerular filtration rate (76 ml/min vs 113 ml/min - p<0.01–). Frequency of aPA positivity was 50% in Patients with IMT >0.600 mm and 33.3% in those with IMT <0.600 mm. If LA positivity was considered separately, it was 41.6% in patients with IMT >0.600 mm and 23.3% in patients with IMT <0.600 mm. Among the 5 patients with IMT >0.7 mm, 2 had LA positivity (40%) vs 10/37 (27%) of those with minor carotid thickness. In conclusion, IMT, a surrogate parameter of atherosclerosis, was correlated with Patients’ age and CRP and not with presence of aPA, even though, in the group of patients with greater IMT, there was a non-significant higher proportion of positivity for anti-phospholipid antibodies, in particular for Lupus Anticoagulant.

Analytical and clinical comparison of different immunoassay systems for the detection of antiphospholipid antibodies

INTRODUCTION

We evaluated analytical and clinical performances of IgG and IgM anticardiolipin (aCL) antibodies and anti-β2-glycoprotein I (a-β2GpI) antibodies and upper limit reference ranges (99th percentiles) in comparison with manufacturer's cutoff values with different commercial methods.

METHODS

We assayed aCL and a-β2GpI in serum samples from 30 healthy individuals, 77 patients with antiphospholipid syndrome (APS) diagnosed according to the Sydney criteria, 51 patients with autoimmune diseases, eight patients with previous thrombotic events, six patients with other diseases, and 18 patients with infectious diseases, using ELISA Inova Diagnostics; EliA Phadia Laboratory Systems; CliA Zenit-RA; and CliA Bio-Flash.

RESULTS

Anticardiolipin and a-β2GpI IgG and IgM immunoassays showed good analytic performances with both 99th percentile and manufacturer's cutoff reference values. Our results showed fair to moderate agreement among assays. In-house cutoff values gave significantly better performances only for a-β2GpI IgG with all the immunoassays analyzed with the exception of Inova CliA Bio-Flash where we obtained the same performances with in-house and manufacturer's cutoffs.

CONCLUSIONS

By guidelines, all laboratories are strongly advised to validate/verify the manufacturer's cutoff values. We recommend establishing low-positive, medium-/high-positive, and high-positive CliA IgG aCL and a-β2GpI ranges in order to help clinicians in the diagnosis and treatment of APS.

Patients with antiphosholipid syndrome and thrombotic recurrences: A real world observation (the Piedmont cohort study)

BACKGROUND

Patients with antiphospholipid syndrome (APS) often have thrombotic recurrences, sometimes despite appropriate ongoing anticoagulant treatment. Identifying APS vascular patients at high risk for thrombotic recurrences is still an unsolved issue.

OBJECTIVES

To report the real-life experience of thrombotic recurrences in APS patients included in the Piedmont observational cohort study, and evaluate clinical and laboratory risk factors for thrombotic recurrences.

PATIENTS

A multi-centre observational study was performed by enrolling 177 patients with vascular APS (primary APS in 99 subjects (56%)); the median follow-up was five years (range 1-26 years).

RESULTS

The observed thrombotic recurrence rate was about 7.5/100 patient years in the first five years after the first thrombotic event. While the first recurrence often occurred (45%) in patients who were not on oral anticoagulant therapy (OAT), the second recurrence mainly occurred despite ongoing OAT (80%). However, due to the real-life observational nature of this study, treatment was based on the treating physician's judgement, and no structured therapeutic protocol was applied. Moreover, compliance with OAT was not available. No differences in antiphospholipid antibodies (aPL) profile were observed between patients with or without thrombotic recurrences, but a high risk aPL profile (Miyakis type 1 and 2a) was present in 96% of our patients, 26% of whom had triple positivity. Diabetes (p < 0.01, OR 10), inherited thrombophilia (p < 0.0078, OR 4) and OAT withdrawal were independent risk factors for recurrences.

CONCLUSIONS

With the limit of a real-life observational cohort study, the thrombotic recurrence rate in APS was as high as 7.5/100 patient years in the first five years after the first thrombotic event. OAT discontinuation, diabetes and inherited thrombophilia, when associated with a high-risk aPL profile, are risk factors for thrombotic recurrences.

[The effects of continuous renal replacement therapy (CRRT) and intermittent haemodialysis (IHD) in the treatment of dabigatran overdose. Case report]

A 85-year-old man, with CKD (e-GFR 35 mL/min), had been given Dabigatran (a direct thrombin inhibitor) at 110 mg daily dose because of atrial fibrillation. Due to intercurrent diarrhea and dehydration, renal function worsened (e-GFR 11 mL/min) and Dabigatran excretion decreased, thereby inducing drug overload. In this case, Dabigatran must be removed by dialysis, but the most appropriate schedule is still undefined. The effects of both continuous haemodiafiltration (CVVHDF) and intermittent haemodialysis (IHD) on plasma Dabigatran (Echarin Chromogenic Assay) were reported. Dialysis clearance of Dabigatran was reported as ratio to urea clearance (Dab/Urea(Cl)). Coagulation was assessed by both DOA-aPTTratio and Thrombin Time-ratio (TTratio). Dabigatran was elevated at 597 ng/mL predialysis (bleeding threshold being 30 ng/mL), and decreased to 96 ng/mL (-84%) after 20 hours of CVVHDF (Urea(Cl) = 67 mL/min). Dab/Urea(Cl) was 0.49. Three hours after dialysis, Dabigatran rebounded to 208 ng/mL. On IHD (Urea(Cl)=238 mL/min), predialysis Dabigatran was 52 ng/mL and decreased to 8 ng/mL (-85%) after 3.5 hours of treatment. Dab/Urea(Cl) was 0.47. Fourteen hours later, Dabigatran rebounded at 19 ng/mL. There was a positive correlation between Dabigatran and TTratio (r = 0.92; p<0.0001), whereas DOA-aPTT did not increase above 2.5 times the reference values, even in face of the highest values of Dabigatran. Therefore, TTratio is more reliable than DOA-aPTT in detecting Dabigatran overdose. Post-dialysis rebound of Dabigatran occurred also with CVVHDF, thereby suggesting that accurate monitoring of both Dabigatran levels and bleeding risk are mandatory, also after long-lasting dialysis sessions.

Thrombotic recurrences and bleeding events in APS vascular patients: a review from the literature and a comparison with the APS Piedmont Cohort

In APS vascular patients, thrombotic recurrences are more frequent than in non-APS thrombotic patients. To better define this clinical setting, a systematic review of the literature after 1999 was performed: 8 cohort studies (including the recent APS Piedmont Cohort) and 6 intervention studies were selected and evaluated. Thrombotic recurrences, bleeding events, therapeutic strategies, antiphospholipid (aPL) profile, inherited and acquired risk factors (when present) were calculated and compared. Emerging risk factors for thrombotic recurrences include withdrawal of oral anticoagulant therapy (OAT), high intensity OAT (INR range 3-4), aPL profile (triple positivity, Miyakis types 1 and 2a profiles) and association with inherited or acquired pro-thrombotic risk factors. Moreover, there are evidences that high risk (mainly for aPL profile) APS vascular patients have a high recurrence rate in spite of correct OAT treatment. Clinical trials in this clinical setting are needed.

Antiphospholipid syndrome in northwest Italy (APS Piedmont Cohort): demographic features, risk factors, clinical and laboratory profile

We report the experience from the Antiphospholipid Antibodies (aPL) Regional Consortium in northwest Italy, meant to support clinical research and foster collaboration among health professionals regarding the diagnosis and management of antiphospholipid syndrome (APS) patients. This cohort-study (APS Piedmont Cohort) was designed to register the clinical characteristics at inception and associated immunological manifestations at diagnosis (if any) of patients who strictly fulfilled the current criteria for APS, all recruited at the Piedmont and Valle d'Aosta regions. Clinical and laboratory data from 217 APS patients (171 with vascular events, 33 with pregnancy morbidity and 13 with both), from 16 centres within the geographical area were collected. Venous thrombosis was recorded in 45.6% of patients, arterial thrombosis in 35%, small-vessel thrombosis in 1.12% and mixed arterial and venous thrombosis in the remaining 19.4% of the cases. Pregnancy morbidity included 19 patients with unexplained fetal death beyond the 10th week of pregnancy, 17 with premature birth before the 34th week and 10 with three or more unexplained spontaneous abortions before the 10th week of gestation. This consortium represents an instrument by which to audit clinical practice, to provide counselling to local centres and to sustain future basic and clinical APS research.

Anti-cardiolipin and anti-β2-glycoprotein I antibodies: normal reference ranges in northwestern Italy

Laboratory tests for anticardiolipin antibodies (aCL) and anti-β2glycoprotein I antibodies (a-β2GPI) face problems common to many autoantibody assays: the lack of a reference standard and the need for each laboratory to assess assay-specific cut-off values. The aims of the study were to evaluate the reference range upper limits (99th percentile) used for aCL and a-β2GPI in the northwest of Italy and to investigate the analytical performances of these assays with the newly obtained reference ranges. We assayed aCL and a-β2GPI in 104 serum samples from patients without a history of thrombosis, pregnancy morbidity, tumours, infections and/or autoimmune diseases (30 males and 74 non-pregnant females). We tested all the commercial assays available in our regions (i.e. Orgentec Diagnostika, Aesku Diagnostics and Inova Diagnostics ELISA; CliA Zenit-RA and EliA Phadia Laboratory Systems). A further 30 serum samples, including 10 from healthy subjects, 10 from antiphospholipid syndrome (APS) patients and 10 from septic patients were assessed to investigate the analytical performance of the obtained cut-off limits. Reference range upper limits obtained with the commercial kits differ among assays and from the values reported by the manufacturer. Moreover, normal reference ranges calculated for IgG and IgM aCL differed from the arbitrary selected laboratory classification values suggested in the guidelines of 40 GPL and MPL.

Prevalence and significance of anti-prothrombin (aPT) antibodies in patients with Lupus Anticoagulant (LA)

OBJECTIVE

Anti-prothrombin (aPT) antibodies have been found in Lupus Anticoagulant (LA) positive patients. Their prevalence and relative contribution to thromboembolic risk in LA-positive patients is not well defined. The aim of this study was to determine their presence and association with thromboembolic events in a large series of patients with confirmed LA.

METHODS

Plasma from LA-positive patients was collected at Thrombosis Centers and sent to a reference central laboratory for confirmation. Positive plasma was tested using home-made ELISA for the presence of aPT and anti-beta(2)GPI antibodies.

RESULTS

LA was confirmed in 231 patients. Sixty-one of 231 (26%, 95%CI 22-33) LA positive subjects were positive for IgG aPT and 62 (27%, 95% CI 21-33) were positive for IgM aPT antibodies. Clinical features of Antiphospholipid Syndrome (APS) were not associated with the presence of IgG aPT [43 APS in 61 (70%) positive and 109 APS in 170 (64%) negative IgG aPT subjects, p=ns] or IgM aPT. Rate of positivity of IgG and IgM a beta(2)GPI was significantly higher than that of IgG and IgM aPT. Clinical events accounting for APS occurred in 97 of 130 (75%) IgG a beta(2)GPI positive and in 55 of 101 (54%) IgG a beta(2)GPI negative patients (OR 2.4, 95% CI 1.4 to 4.3, p=0.002). No significant association with clinical events in patients positive for both IgG aPT and IgG a beta(2)GPI as compared to those positive for one or another test was found. When patients negative for both IgG aPT and IgG a beta(2)GPI (LA positive only) were compared with remaining patients, a significantly lower association with clinical events was found (OR=0.4, 95% CI: 0.2 to 0.7, p=0.004).

CONCLUSIONS

As compared to IgG a beta(2)GPI, the prevalence of IgG aPT in patients with LA is significantly lower and not associated with the clinical features of APS.

Presence of low titre of antiphospholipid antibodies in cancer patients: a prospective study

Antiphospholipid antibodies (aPL) represent a well-defined risk factor for thrombotic events. aPL have been observed in the plasma of cancer patients, but the role and clinical relevance of aPL in this clinical setting is still unclear. This is a prospective cohort study whose aims were to: (1) compare the prevalence of aPL antibodies in cancer patients at diagnosis to matched control subjects; (2) compare thrombosis-free survival and overall survival in aPL positive and aPL negative cancer patients. One hundred and thirty-seven patients were enrolled upon a diagnosis of cancer, and were screened for lupus anticoagulant (LA), anticardiolipin antibodies, and anti-beta2 glycoprotein I antibodies (IgG and IgM). Two years of follow-up were scheduled. Low-titre aPL antibody positivity was found in 33 patients (24%), and in 6 controls (4.3%; P < 0.0001). During follow-up, nine patients developed a symptomatic, objectively confirmed, thromboembolic event. One thrombotic event was observed among the 33 aPL positive patients (3%), and 8 among the 104 aPL negative ones (7.6%) (P = NS). During follow-up, 21 patients died, and among them, 3 (9.1%) were aPL positive and 18 (17.3%) were aPL negative (P = 0.39; C.I. 0.28-0.05). In conclusion, a high prevalence of low-titre aPL was found in cancer patients at diagnosis, but no statistical difference in thrombosis-free survival or in overall survival was observed between aPL positive and aPL negative patients.

Survey of lupus anticoagulant diagnosis by central evaluation of positive plasma samples

OBJECTIVE

To determine whether the diagnosis of lupus anticoagulant (LAC) in a large cohort of positive patients was confirmed at a reference laboratory.

METHODS

Over a 1-year period, each participating center collected samples from LAC-positive patients. Plasma was filtered and kept deep-frozen until it was sent on dry ice to the reference laboratory by express courier. Centers returned detailed laboratory information and clinical data from each patient. The reference laboratory screened plasma samples by diluted Russell viper venom time (dRVVT) and kaolin clotting time (KCT). When these were prolonged, 1:1 mixing studies were carried out, and confirmatory tests were performed as appropriate. Positive samples were further tested by thrombin time (TT). The presence of heparin was checked by measuring antifactor Xa activity when TT was prolonged. Negative samples were tested by activated partial thromboplastin time using hexagonal phospholipids.

RESULTS

Plasma samples from 302 patients from 29 anticoagulation clinics were analyzed. LAC was excluded in 71 samples (24%), because dRVVT and KCT screening test results were normal (34) or reversed to normal by mixing studies (35). The remaining two samples were considered negative because they contained heparin. LAC-negative patients showed different characteristics from those in whom diagnosis was confirmed. They were significantly older (49.7 vs. 45.0 years, P < 0.03), were more often first diagnosed (66% vs. 41%, P < 0.001), and were more frequently judged as mild in LAC potency (60% vs. 25%, P < 0.0001). Moreover, anticardiolipin and anti-beta(2)-glycoprotein I antibody values were more often normal in LAC-negative (82%) than in LAC-positive (42%) samples (P < 0.0001). LAC-positive samples identified by both dRVVT and KCT (146/231, 63%) showed a LAC potency that was significantly stronger than that in samples in which LAC diagnosis was made by a single test.

CONCLUSIONS

A false-positive LAC diagnosis is not uncommon across specialized centers. Patients' characteristics and a complete antiphospholipid antibody profile may help to identify these individuals.

Antiphospholipid antibodies and hypertension

Hypertension is a common manifestation of antiphospholipid syndrome (APS). Antiphospholipid antibodies (aPL) have been described in patients with hypertension secondary to renal artery stenosis (RAS). Twenty-six patients with RAS and 25 patients with severe essential hypertension (diastolic blood pressure > 110 mmHg or > or = 3 hypertensive drugs) were studied and compared to 61 age- and sex-matched healthy subjects. Serum samples were tested for lupus anticoagulant (LA), anticardiolipin (aCL) IgG and IgM, antiprothrombin (aPT) IgG and IgM, anti-beta2glycoprotein 1 (abeta2GP1) IgG and IgM. aPL were negative in all patients with RAS. Two patients with essential hypertension had positive aPL (8%) (LA in one patient confirmed in a second assay and abeta2GP1-IgG in the other patient confirmed one year later together with aCL IgG positivity). Among healthy subjects, one case (1.6%) was found to be positive for LA, aCL IgM, abeta2GP1 IgM, aPT IgG, aPT IgM. In conclusion, the association between RAS and aPL seems to be casual rather than an expression of an elective thrombotic localization ofAPS. The positive finding of aPL in 8% of patients with essential hypertension, a frequency higher than that of the control population, deserves further studies in larger series to better explore the relationship between aPL and hypertension.

Catastrophic antiphospholipid syndromes in systemic lupus erythematosus

The objective of this study was to look for the occurrence of catastrophic antiphospholipid syndromes (APS) and to try to detect discriminating factors for predicting a worse prognosis, related to Lupus anticoagulant (LA) and antiphospholipid antibodies (aPL), in systemic lupus erythematosus (SLE) with main renal involvement. Regression, recursive partition and logistic regression analyses were applied to our 80 SLE patients prospectively followed up since 1980. Immunologic and other laboratory parameters including beta 2-glycoprotein 1 dependence, resistance to activated protein C caused by a substitution on the coagulation factor V gene, induction of monocyte procoagulant activity. Regression studies demonstrated an overall worse prognosis in term of both thrombosis and death for the group of LA/aPL positive patients (33/80). However, recursive partition analysis was able to isolate a small high risk-subgroup (8/33) characterized by persistent LA/aPL antibodies positive result, widespread signs of noninflammatory vasculopathy (skin, brain, kidney) and renal pathology mimicking that of thrombotic microangiopathy or arteriolosclerosis, also in the absence of classic SLE-nephritis. Only in this subset, three catastrophic APS were recorded, while, in traditional SLE nephritis, even persistent LA/aPL positive results (sometimes after one previous thrombosis) did not seem to imply a particularly severe prognosis. All serologic criteria employed are unable to identify high-risk patients. We conclude that catastrophic APS is a rare event in renal SLE. Before more predictive serologic markers become available, a simple algorithm, dealing with clinical data and renal histologic patterns, may help physicians to identify putatively high risk-LA/aPL antibodies in SLE patients with main renal involvement. This ominous subset does not belong to the group of classic SLE-nephritis.

Use of modified functional assays for activated protein C resistance in patients with basally prolonged aPTT

Inherited resistance to activated protein C (APCr) is currently recognized as the most prevalent cause underlying venous thrombophilia, with an estimated prevalence around 20% in thrombotic patients and around 1.8-7% in the general population. A correct laboratory diagnosis of APCr is therefore essential. Two different diagnostic approaches are at present at our disposal: the semi-quantitative plasma test based on the measurement of two aPTTs (in the presence and absence of activated protein C), and the detection of the factor V Arg506 Gln mutation by DNA analysis. In this study we firstly evaluated sensitivity, specificity and diagnostic efficiency of an aPTT-based plasma clotting test (Chromogenix, Sweden) versus DNA analysis; then, since the APC resistance test is invalidated by a basally prolonged aPTT (i.e. during warfarin and heparin therapy or in patients with clotting factor deficiencies or in the presence of a lupus anticoagulant), patient plasmas were conveniently diluted in factor V deficient plasma in order to correct clotting factor abnormalities. Nevertheless, patients with a LA and an aPTT ratio range 1.8-3.17 were still all misclassified. We obtained correct diagnoses in LA positive patients by preincubating plasmas with a mixture of phospholipids; therefore we decided to perform a double modified clotting test adding a mixture of platelet derived phospholipids to samples previously diluted in factor V deficient plasma. The performance characteristics of this novel method with a different aPTT reagent (Behring, Germany) were also evaluated. With this double modified test all patients were correctly classified as negative or positive for factor V mutation in agreement with DNA analysis, irrespectfully of the basal aPTT value and the aPTT reagent employed. We propose this modified version of the APCr clotting test as an easily reproducible, reliable, very sensitive and specific screening test which possibly reduces the need for DNA analysis.

Natural and acquired inhibitors of hemostasis in selected symptomatic outpatients with venous thromboembolic disease

BACKGROUND AND OBJECTIVE

Deficiencies of natural inhibitors and the presence of lupus anticoagulant are important risk factors leading to venous thromboembolic events. Before resistance to activated protein C (APC-R) was identified, the overall prevalence of inherited abnormalities of hemostasis in non-selected outpatients with venous thromboembolic disease was under 10%. This cast doubts on the of cost effectiveness and clinical significance of assaying hemostasis inhibitors in all such patients. The goal of this study is to evaluate the prevalence of inherited and acquired abnormalities of hemostasis in younger symptomatic outpatients with objectively diagnosed venous thromboembolic disease (VTD).

METHODS

From October 1994 to October 1996, we diagnosed, treated and followed 191 consecutive outpatients with an objective diagnosis of venous thromboembolic disease, and assayed natural and acquired hemostasis inhibitors in 81 of them aged less than 50; in addition, 129 relatives of patients with inherited deficiencies were evaluated.

RESULTS

Twenty-six of the patients under age 50 showed inherited deficiencies of natural inhibitors (3 antithrombin, 5 protein C, 3 protein 5 and 14 APC-R, 1 dysfibrinogenemia) and 8 patients had lupus anticoagulant (LA): abnormalities of hemostasis were found in 41.9% (95% confidence interval 31.1-53.5). In older selected patients, 60% (95% confidence interval 40.6-77.3) of the subjects showed abnormalities. Seventy-two of the relatives displayed natural inhibitor deficiencies; 88.5% of the families studied had at least one relative with the same defect as the propositus.

INTERPRETATION AND CONCLUSIONS

A simple selection based on age, clinical and family history shows the existence of a high prevalence and the important clinical significance of abnormalities of hemostasis in symptomatic outpatients with venous thromboembolic disease.

Lupus anticoagulant and thrombosis: role of von Willebrand factor multimeric forms

OBJECTIVE

Patients with lupus anticoagulant (LA) have an increased incidence of venous and arterial thrombosis whose pathogenesis is still unclear. High molecular weight von Willebrand Factor (vWF) multimers seem to play a causal role in shear stress-induced platelet aggregation and thrombus formation. We studied whether in patients with LA, alterations in the vWF multimers might coexist.

METHODS

The multimeric composition of plasma vWF was analysed by SDS-electrophoresis and immunoblotting in 43 subjects positive for LA. About 2/3 of the patients had had either ischemic stroke, recurrent abortions, deep vein thrombosis (DVT) or a combination of these; the remaining subjects had never had any thrombotic events.

RESULTS

An abnormal vWf multimeric pattern was found in 16 patients (37.2%); no correlation was found with the diagnosis, but the presence of abnormal vWF significantly correlated with the site of the thrombosis: indeed, it was never detected in subjects with DVT, but was found in 71.4% of patients with multiple abortions, in 50% of those with stroke and even in 25% of non-thrombotic patients.

CONCLUSION

The hypothesis is put forward that abnormal VWF may represent an additional risk factor to LA for arterial thrombosis.

Factor V Arg506-->Gln mutation in patients with antiphospholipid antibodies

Antiphospholipid antibodies (APA) have thought to be implicated in the pathogenesis of both arterial and venous thrombosis. Because of heterogeneity of APA, direct evidence of their involvement in a thrombotic event is not yet available. Development of thrombosis in the antiphospholipid antibody syndrome (APS) may occur because of the presence of additional risk factors. Here we have analysed 60 patients with APA for the presence of the Arg506-->Gln mutation in factor V. Among them 26 suffered from deep venous thrombosis, 13 from arterial thrombosis and 21 had no history of arterial or venous thrombosis. In the first group four patients were found to be heterozygous and one homozygous for the factor V Arg506-->Gln mutation. None of the patients with the factor V mutation was found in the second and third group. The incidence of factor V mutation was significantly elevated in the group of patients with venous thrombosis. These data suggest that in patients with antiphospholipid antibodies the factor V Arg506-->Gln mutation may play a major role in the occurrence of venous thrombosis.

Arterial and venous thrombosis in two Italian families with the factor V Arg506-->Gln mutation

APC resistance, due to a point mutation in factor V at amino acid position Arg506, has been identified as a major cause of inherited thrombophilia. Here we report the presence of the factor V Arg506-->Gln mutation in 2 Italian families. In 1 family 3 subjects heterozygous and 2 subjects homozygous for the factor V Arg506-->Gln mutation were identified. The only subject who developed a thrombotic event was a 20-yr-old girl who was found to be homozygous for the factor V Arg506-->Gln mutation. In the second family 10 subjects were identified to be heterozygous for the factor V Arg506-->Gln mutation; among them 2 developed a thrombotic event. In the same family 2 individuals were found to be homozygous for the mutation: the first had a myocardial infarction at age 25 yr and the second suffered from multiple episodes of deep venous thrombosis and had a stroke at age 24 yr. These data show that the risk of developing deep venous thrombosis for the carriers of the factor V Arg506-->Gln mutation is high in the families investigated. Furthermore our data imply that the factor V Arg506-->Gln mutation in its homozygous form may relate to myocardial infarction and stroke.

Absence of mutations at the activated protein C cleavage sites of factor VIII in 125 patients with venous thrombosis

Resistance to activated protein C (APC), caused by a mutation at amino acid position Arg506 of the factor V gene, has recently been identified as the most prevalent genetic defect associated with venous thrombosis. Similarly to factor V, mutations at the cleavage sites of factor VIII for APC may occur in patients with venous thrombosis. Here we have analysed 125 consecutive patients with incidental or recurrent venous thromboembolism for the presence of mutations at the cleavage sites for APC at amino acid positions Arg336 and Arg562 of factor VIII. Our findings indicate that mutations at these amino acid positions of factor VIII do not occur in the patient group analysed.