Corrigendum: The new Italian registry of infantile thrombosis (RITI): a reflection on its journey, challenges and pitfalls.

[This corrects the article DOI: 10.3389/fped.2023.1094246.].

The new Italian registry of infantile thrombosis (RITI): A reflection on its journey, challenges and pitfalls.

Introduction: Thrombotic events in neonates and children represent a rare although severe occurrence in view of the associated risk of mortality and sequelae. Quality evidence is limited in this field, and registry studies provide an essential base for research. The aim of this paper is to present the new Italian Registry of Infantile Thrombosis (RITI), set it into the scene of international thrombosis and stroke registries, and provide some insight on the challenges associated with registry management. Methods: We present the detailed structure and content of the new RITI registry, a brief overview of its main data, and a reflection on its features, pitfalls and the main challenges related to its management. Results: The RITI, initially started in 2007 and officially re-launched in 2017 after structural modifications, is a non-interventional retrospective and prospective registry study collecting data on neonatal and pediatric patients (0-18 years) who experienced a systemic or cerebral thrombotic event in Italy. The RITI is managed by a multidisciplinary team with expertise in pediatric thrombosis, and participation is open to all Italian physicians, on a voluntary basis. The overall aim of the registry is to acquire new evidence to better characterize the population of children with thrombotic events and improve their management and outcome. 48 Italian pediatric and intensive care units are actively involved in the RITI, including 85 medical doctors from 16 Italian regions. A total of 1,001 neonates and children affected by cerebral or systemic thrombosis have been enrolled. Discussion: The RITI is one of the largest available European registries of neonatal and pediatric thrombosis. National registries like the RITI represent a model for the study of rare conditions based on multidisciplinary and multicenter collaboration, aimed at overcoming the limitations due to small populations of patients, and creating a network of experts for patient referral and continuous education. Moreover, registry studies have a pivotal role in the research on pediatric thrombosis, due to the limited feasibility of high-quality studies. In our experience, the main critical stages, pitfalls and challenges in registry management include adequate registry designing, diffusion, data completeness and quality control.

Prevalence of inherited thrombophilia in patients with documented stent thrombosis.

BACKGROUND: Stent thrombosis (ST) is a multi-factorial process involving different mechanisms. The impact of inherited coagulation disorders in the genesis of ST has never been assessed. The aim of the present study was to evaluate the prevalence of G1691A Factor V Leiden mutation, G20210A Factor II (prothrombin) mutation and C677T homozygous methylenetetrahydrofolate reductase (MTHFR) polymorphism in patients with ST. METHODS AND RESULTS: The prevalence of the aforementioned gene variations was assessed in 127 patients: 50 admitted for ST and 77 previously treated with percutaneous coronary intervention not developing ST. A control cohort of 529 healthy volunteers was sampled from the same geographical area. Patients with ST were carriers of at least 1 gene variation in 28% of cases. The prevalence of G1691A Factor V Leiden mutation (odds ratio [OR]=0.64; 95% confidence interval [CI]: 0.04-10.5), G20210A Factor II mutation (OR=0.63; 95% CI: 0.12-3.28) and C677T MTHFR homozygous polymorphism (OR=1.13; 95% CI: 0.47-2.72) did not differ significantly among patients with or without ST. The logistic regression model did not show a significant association between gene variations and ST (OR=0.61; 95% CI: 0.24-1.60; P=0.32). CONCLUSIONS: A specific association between studied gene variations and ST has not been detected. The relatively high prevalence of at least 1 gene anomaly in such a rare subset of patients, and its consequences in term of secondary prevention therapy, suggests that screening for thrombophilia might be justifiable in cases of ST.

Predictors of migraine subtypes in young adults with ischemic stroke: the italian project on stroke in young adults.

BACKGROUND AND PURPOSE: the mechanisms underlying the relationship between migraine and ischemic stroke remain uncertain. The aim of the present study was to investigate the predictive value of major cardiovascular risk factors, cardiac interatrial abnormalities, and additional biological markers on migraine subtypes in young adults with ischemic stroke. METHODS: ischemic stroke patients aged 45 years or younger were consecutively enrolled as part of the Italian Project on Stroke in Young Adults. A comprehensive evaluation was performed including assessment of self-reported migraine and cardiovascular risk factors, interatrial right-to-left shunt, and genotyping to detect factor V Leiden and the G20210A mutation in the prothrombin gene. RESULTS: nine hundred eighty-one patients (mean age, 36.0 ± 7.6 years; 50.7% women) were included. The risk of migraine with aura increased with decreasing number of cardiovascular risk factors (OR, 0.50; 95% CI, 0.24-0.99 for 2 factors or more), increasing number of thrombophilic variants (OR, 2.21; 95% CI, 1.05-4.68 for carriers of at least 1 of the 2), and the presence of right-to-left shunt (OR, 2.41; 95% CI, 1.37-3.45), as compared to patients without migraine. None of these factors had influence on the risk of migraine without aura. CONCLUSIONS: in young adults with ischemic stroke, low cardiovascular risk profile, right-to-left shunt, and an underlying procoagulant state are predictors of migraine with aura. The biological effects of these factors should be considered in future studies aimed at investigating the mechanisms linking migraine to brain ischemia.

Is there a relationship between factor V Leiden and type 2 diabetes?

BACKGROUND: Diabetes is well known risk factor for thrombotic events. The association between diabetes and venous thromboembolism is still matter of debate. However, during diabetes an acquired thrombophilia is present and is due to the non-enzymatic glycosilation of clotting inhibitors as antithrombin thus leading to hypercoagulable state. A possibile relationship between the presence of FVL gene variant in type 1 or type 2 diabetes has been hypothysed by several reports in the Literature with non-univocal findings. PATIENTS AND METHODS: Retrospectively we analysed nearly 7000 patients referred to our Thrombosis Center for venous thromboembolism (VTE) then we selected 115 patients underwent to the screening for inherited thrombophilia. All selected patients were divided in 2 groups: the first group (group A) included 64 patients with previous VTE and carriers of factor V Leiden, while the second group (group B) included 51 patients with previous VTE and evetually carriers of thrombophilic defects other than factor V Leiden. Patients of group B acted as control group. 75 g oral glucose tolerance Test (OGTT) recommended by WHO was perfomed to all subjects in the study in order to screen subjects with glucose reduced tolerance or subjects with inducible diabetes. Statistical analysis was performed with STATA 6 http://www.stata.com with Student t test for unpaired data, with chi2 test or with Fisher exact test where appropriated; differences were considered to be significant if p < 0.05. RESULTS: We did not find sifferences between glycaemia at baseline and after OGTT between patients with VTE carriers of FVL compared to non-carriers of FVL. We found a relevant increase in the prevalence of IGT and diabetes between patients with VTE carriers of FVL compared to non-carriers of FVL although this increase did not raise statistical significance. DISCUSSION: our data pointed out an interesting aspect of the linking between FVL gene variant, diabetes and atherothrombosis and other vascular complications, although data on larger population are needed; this aspect may be another relevant topic of research based because also a link between the pathogenesis of venous thrombosis and atherothrombosis has been recently reported in the Literature.

Paediatric venous thromboembolism: a report from the Italian Registry of Thrombosis in Children (RITI).

BACKGROUND: The Italian Registry of Thrombosis in Children (RITI) was established by a multidisciplinary team with the aims of improving knowledge about neonatal and paediatric thrombotic events in Italy and providing a preliminary source of data for the future development of specific clinical trials and diagnostic-therapeutic protocols. MATERIALS AND METHODS: We analysed the subset of RITI data concerning paediatric systemic venous thromboembolic events that occurred between January 2007 and June 2013. RESULTS: Eighty-five deep venous thromboses and seven pulmonary emboli were registered in the RITI. A prevalence peak was observed in children aged 10 to 18 years and, unexpectedly, in children aged 1 to 5 years. A central venous line was the main risk factor (55% of venous thromboembolic events); surgery (not cardiac) (25%), concomitant infections (23%) and malignancy (22%) were the clinical conditions most often associated with the onset of venous thromboembolism. There was a diagnostic delay of more than 24 hours in 37% of the venous thromboembolic events. Doppler ultrasound was the most widely used test for the objective diagnosis of deep venous thrombosis (87%). Antithrombotic therapy was administered in 96% of venous thromboembolic events, mainly low molecular weight heparin (60%). In 2% of cases recurrences occurred, while post-thrombotic syndrome developed in 8.5% of cases. DISCUSSION: Although the data from the RITI are largely in agreement with published data, peaks of prevalence of thrombosis, risk factors and objective tests used for the diagnosis showed some peculiarities which may deserve attention.

SV-IV Peptide1-16 reduces coagulant power in normal Factor V and Factor V Leiden.

Native Factor V is an anticoagulant, but when activated by thrombin, Factor X or platelet proteases, it becomes a procoagulant. Due to these double properties, Factor V plays a crucial role in the regulation of coagulation/anticoagulation balance. Factor V Leiden (FVL) disorder may lead to thrombophilia. Whether a reduction in the activation of Factor V or Factor V Leiden may correct the disposition to thrombophilia is unknown. Therefore we tested SV-IV Peptide 1-16 (i.e. a peptide derived by seminal protein vescicle number IV, SV-IV) to assess its capacity to inhibit the procoagulant activity of normal clotting factor V or Factor V Leiden (FVL). We found that SV-IV protein has potent anti-inflammatory and immunomodulatory properties and also exerts procoagulant activity. In the present work we show that the SV-IV Peptide 1-16, incubated with plasma containing normal Factor V or FVL plasma for 5 minutes reduces the procoagulant capacity of both substances. This is an anticoagulant effect whereas SV-IV protein is a procoagulant. This activity is effective both in terms of the coagulation tests, where coagulation times are increased, and in terms of biochemical tests conducted with purified molecules, where Factor X activation is reduced. Peptide 1-16 was, in the pure molecule system, first incubated for 5 minutes with purified Factor V then it was added to the mix of phosphatidylserine, Ca2+, Factor X and its chromogenic molecule Chromozym X. We observed a more than 50% reduction in lysis of chromogenic molecule Chromozym X by Factor Xa, compared to the sample without Peptide 1-16. Such reduction in Chromozym X lysis, is explained with the reduced activation of Factor X by partial inactivation of Factor V by Peptide 1-16. Thus our study demonstrates that Peptide 1-16 reduces the coagulation capacity of Factor V and Factor V Leiden in vitro, and, in turn, causes factor X reduced activation.

Homocysteine, MTHFR C677T gene polymorphism, folic acid and vitamin B 12 in patients with retinal vein occlusion.

BACKGROUND: Many available data have suggested that hyperhomocysteinaemia, an established independent risk factor for thrombosis (arterial and venous), may be associated with an increased risk of retinal vein occlusion (RVO). AIM OF THE STUDY: To evaluate homocysteine metabolism in consecutive caucasian patients affected by RVO from Northern Italy. PATIENTS AND METHODS: 69 consecutive patients from Northern Italy (mean age 64.1 +/- 14.6 yy) with recent RVO, were tested for plasma levels of homocysteine (tHcy: fasting and after loading with methionine), cyanocobalamine and folic acid levels (CMIA-Abbot) and looking for MTHFR C677T mutation (Light Cycler-Roche) and compared to 50 volunteers, enrolled as a control group. RESULTS: Fasting levels of tHcy were significantly higher in patients than in controls: mean value 14.7 +/- 7.7 vs 10.2 +/- 8 nmol/ml. Post load levels were also significantly higher: mean value 42.7 +/- 23.7 vs 30.4 +/- 13.3 nmol/ml; Total homocysteine increase was also evaluated (i.e. Delta-tHcy) after methionine load and was also significantly higher in patients compared to control subjects: mean Delta-tHcy 27.8 +/- 21.5 vs 21.0 +/- 16 nmol/ml (normal value < 25 nmol/ml). Furthermore, patients affected by RVO show low folic acid and/or vitamin B12 levels, although differences with control group did not reach statistical significance. Heterozygous and homozygous MTHFR mutation were respectively in study group 46% and 29% vs control group 56% and 4%. CONCLUSION: our data confirm that hyperhomocysteinaemia is a risk factor for RVO, and also that TT genotype of MTHFR C677T is more frequently associated with RVO: if the mutation per se is a risk factor for RVO remains an open question to be confirmed because another study from US did not reveal this aspect. Hyperomocysteinemia is modifiable risk factor for thrombotic diseases. Therefore, a screening for tHcy plasma levels in patients with recent retinal vein occlusion could allow to identify patients who might benefit from supplementation with vitamins and normalization of homocysteine levels, in fasting and after methionine load.

Paediatric arterial ischaemic stroke and cerebral sinovenous thrombosis. First report from the Italian Registry of Pediatric Thrombosis (R. I. T. I., Registro Italiano Trombosi Infantili).

Data from large case series of children with cerebral thrombotic events are pivotal to improve prevention, early recognition and treatment of these conditions. The Italian Registry of Pediatric Thrombosis (R. I. T. I.) was established in 2007 by a multidisciplinary team, aiming for a better understanding of neonatal and paediatric thrombotic events in Italy and providing a preliminary source of data for the future development of specific clinical trials and diagnostic-therapeutic protocols. We analysed data relative to the paediatric cerebral thrombotic events of the R. I. T. I. which occurred between January 2007 and June 2012. In the study period, 79 arterial ischaemic stroke (AIS) events (49 in males) and 91 cerebral sinovenous thrombosis (CSVT) events (65 in males) were enrolled in the R. I. T. I. Mean age at onset was 4.5 years in AIS, and 7.1 years in CSVT. Most common modes of presentation were hemiparesis, seizures and speech disturbances in AIS, and headache, seizures and lethargy in CSVT. Most common etiologies were underlying chronic diseases, vasculopathy and cardiopathy in AIS, and underlying chronic diseases and infection in CSVT. Time to diagnosis exceeded 24 hours in 46 % AIS and 59 % CSVT. Overall data from the Italian Registry are in substantial agreement with those from the literature, despite small differences. Among these, a longer time to diagnosis compared to other registries and case series poses the accent to the need of an earlier recognition of paediatric cerebrovascular events in Italy, in order to enable prompt and effective treatment strategies.

Evaluation of the prevalence of severe hyperhomocysteinemia in adult patients with thrombosis who underwent screening for thrombophilia.

INTRODUCTION: Treatment with B-vitamins and betaine reduces the high risk of thrombosis in patients with homocystinuria, a metabolic syndrome that is characterized by severe hyperhomocysteinemia (HHcy). In contrast, there is no clear demonstration that B-vitamins reduce the risk of thrombosis in patients with mild HHcy: for this reason, many question the clinical utility of measuring total Hcy (tHcy) in patients with thrombosis. However, thrombosis may be the first clinical manifestation of homocystinuria in patients reaching adulthood without signs and symptoms of the syndrome. AIM: 1) to measure the prevalence of severe, previously undiagnosed, HHcy among patients with thrombosis 2) to profile these patients on the basis of their characteristics. METHODS: Six Italian Thrombosis Centers completed a first questionnaire, reporting tHcy levels in patients with thrombosis who underwent thrombophilia screening, and a second questionnaire, reporting the characteristics of patients with severe HHcy (tHcy>100µmol/L). RESULTS: Of 19,678 cross-sectionally collected patients with thrombosis who underwent thrombophilia screening in the last 12.5years (median value, range 6-17), 38 had severe HHcy (0.2%). Their median age at diagnosis was 47years (range 19-83) and the median level of tHcy was 130µmol/L (range 101-262). Venous thromboembolism (71%) was more frequent than arterial thromboembolism (26%); recurrent thrombosis occurred in 42% of cases. CONCLUSIONS: Measurement of tHcy in adult patients with thrombosis may reveal the presence of severe HHcy. Since treatment of patients with severe HHcy decreases the risk of thrombosis, measurement of tHcy in patients with thrombosis may prove clinically useful.

Interaction between proatherosclerotic factors and right-to-left shunt on the risk of cryptogenic stroke: the Italian Project on Stroke in Young Adults.

OBJECTIVE: To explore the interaction effects between cardiac interatrial right-to-left shunt (RLS) and proatherosclerotic factors on the risk of brain ischaemia. DESIGN: Multicentre Italian case-control study. SETTING: University hospitals. PARTICIPANTS: 588 patients with cryptogenic stroke (CS) aged ≤45 years and 585 control subjects consecutively enrolled as part of the Italian Project on Stroke in Young Adults. METHODS: Interaction effects between RLS and an individual proatherosclerotic score computed from the number of conventional vascular risk factors for the risk of CS were investigated. Data were examined by logistic regression models and expressed as interaction OR or interaction risk difference (RD). RESULTS: CS risk increased with increasing number of proatherosclerotic factors in subjects without RLS (OR 2.73; 95% CI 1.98 to 3.76; RD +0.246; 95% CI +0.17 to +0.32; for subjects with one or more factors), but was higher in subjects with RLS and no additional proatherosclerotic factors (OR 5.14; 95% CI 3.49 to 7.58; RD +0.388; 95% CI +0.31 to +0.47) compared with subjects without RLS and no risk factors. Negative interaction and antagonistic effects between RLS and proatherosclerotic factors were observed (interaction OR 0.52; 95% CI 0.31 to 0.91; interaction RD -0.17; 95% CI -0.29 to -0.05). CONCLUSIONS: The influence of RLS on the risk of CS decreases with increasing number of atherosclerotic factors, and is highest when such factors are absent. Individual proatherosclerotic profiles may help to identify patients with CS whose patent foramen ovale is probably pathogenic.

Low-molecular-weight heparin in women with repeated implantation failure.

UNLABELLED: Implantation failure is common in assisted reproduction techniques (ART). The role of low-molecular-weight heparin (LMWH) is a matter of debate as a potential factor to improve implantation. AIM: To evaluate the pregnancy rate in patients with or without heparin administration. MATERIALS & METHODS: We performed a retrospective observational analysis of patients with at least two IVF/intracytoplasmic sperm injection cycles with implantation failure, screened for inherited thrombophilia and submitted to further ART cycles with or without administration of LMWH. A total of 265 patients fulfilled the enrollment criteria. Of these 149 (56%) were primary infertile and 116 (44%) were secondary infertile. Their mean age was 36.3 ± 3.6 years. We analyzed basal FSH, smoking habit, gene variants for inherited thrombophilia (i.e., MTHFR C677T, prothrombin G202A10G and Factor V Leiden). The patients underwent 569 new ART cycles: 512 (90%) without and 57 (10%) with LMWH. RESULTS: In total 105 clinical pregnancies were observed in 569 cycles (18.8%). The pregnancy rate was 17.19% (88/512) in patients not treated with LMWH and 29.52% (17/57) in the LMWH-treated group (p = 0.006). In women over 36 years of age the pregnancy rate was 15.53% (50/322) in nontreated versus 35.71% (10/28) in treated cycles (p = 0.007), while no difference was found in younger women. No statistical difference was found between the presence of inherited thrombophilia and pregnancy rate in treated and untreated cycles. DISCUSSION: significantly higher pregnancy rate in patients with previous ART implantation failures was observed with LMWH. Our results confirm no relation among inherited thrombophilia and pregnancy rate in patients with previous IVF implantation failures. These findings should be confirmed by randomized controlled trials before use of LMWH for ART cycles is recommended.

Differences in the INR evaluation of two different thromboplastins in patients with positivity to lupus anticoagulant in ongoing oral anticoagulation.

BACKGROUND: A possible interference between lupus anticoagulant (LAC), a well characterized clotting inhibitor, in the International Normalized Ratio (INR) determination during oral anticoagulation (OA) has been reported in the literature. Few data are available about the relationship between this kind of interference and the daily clinical management of oral anticoagulation. The aim of the study is to evaluate the role of two different thromboplastins-RecombiPlasTin 2G and HepatoComplex-in the determination of INR values of several patients' ongoing OA for a previous thrombotic disorder with and without positivity to LAC, and to evaluate possible interferences in the daily therapeutic approach. PATIENTS AND METHODS: We selected 16 patients (13 females and 3 males, mean age 59 ± 16 years) with LAC positivity ongoing OA and 11 control subjects (7 females and 4 males, mean age 58 ± 14.5 years) with similar characteristics (ie, ethnic background and weight) with LAC negativity ongoing OA. 165 assays for INR determination were analyzed from both groups. Statistical analysis was performed using STATA 10 software. P values were considered significant if <0.05. RESULTS: Mean values of INR for patients with LAC positivity were 3.79 ± 1.63 when tested with RecombiPlasTin 2G vs 3.18 ± 1.15 when tested with HepatoComplex (P < 0.001, s); while mean values of INR for patients with antiphospholipid syndrome (APS) with LAC negativity were 3.54 ± 1.39 when tested with RecombiPlasTin 2G vs 3.23 ± 1.14 when tested with HepatoComplex (P < 0.002, s). An INR value > than 4.5 was found in 31/165 samples in 9 subjects, 8 patients with LAC positivity, and 1 control group subject with LAC negativity. There was a great difference in INR values in these subjects if we use the common thromboplastin (ie, RecombiPlasTin 2G) with a INR range varying from 5.14 ± 0.35 vs 3.79 ± 0.38 if we use another thromboplastin (ie, HepatoComplex) (P < 0.001, s). A change in the therapeutic approach for OA is possible in these cases because different INR values were obtained using different thromboplastins. DISCUSSION: Our data confirm that INR evaluation does not reveal significant changes also if tested with two different thromboplastins, for patients ongoing OA with and without LAC positivity, when the INR value is < than 4. Over this INR value there is a significant difference in patients with LAC positivity if we use a different thromboplastin for the INR determination. For this reason values obtained by RecombiPlasTin 2G need to be confirmed and matched with another thromboplastin (ie, HepatoComplex). This approach may be useful in order to have a good INR testing for the chronic long-term treatment with OA in particular in patients with LAC positivity.

Intima-media thickness evolution after treatment with infliximab in patients with rheumatoid arthritis.

BACKGROUND: Atherosclerosis is a well known progressive disease that recognizes risk factors such as diabetes, hypertension, smoking, dyslipidemia, and inflammation. Mechanisms underlying atherosclerotic processes during inflammation are not completely understood, but cytokines are also involved, in particular tumor necrosis factor-alpha (TNF-alpha). Chronic inflammatory diseases such as rheumatoid arthritis (RA) are commonly associated with atherosclerotic complication. Little is known about the role of treatment of chronic inflammatory disease on the evolution of atherosclerosis in this kind of disease. Usually, evolution of atherosclerosis is monitored by intima-media thickness and the presence of plaques on several arteries such as common carotid. AIM: The aim of the study was to monitor atherosclerosis evolution in seven RA patients on common treatment with infliximab (an anti-TNF-alpha drug) compared with seven RA patients during common treatment but not treated with infliximab. PATIENTS AND METHODS: We selected 14 patients with RA according to the American College of Rheumatology classification criteria. Seven patients were selected before and after common treatment for RA based on nonsteroidal anti-inflammatory drugs (NSAIDs), methotrexate, and steroids (12 months), and seven patients before and after treatment based on infliximab associated with NSAIDs, methotrexate, and steroids (12 months). Ultrasound vascular imaging was performed to screen intima-media thickness and the presence of atherosclerotic plaques on common carotid artery and identify evolution of atherosclerosis. RESULTS: After 12 months, patients that were treated with infliximab showed significant worsening of atherosclerosis with an increase of intima-media thickness and the presence of further atherosclerotic plaques compared to patients that were treated traditionally and showed a nonsignificant increase of the same parameters. DISCUSSION: Treatment based on anti-TNF-alpha such as infliximab shows a worsening evolution of atherosclerosis based on our data. If these data are associated with a poor clinical outcome such as atherothrombosis of cerebral vessels and/or coronary vessels, this should be evaluated by further studies.

Effects of CYP2C9 and VKORC1 on INR variations and dose requirements during initial phase of anticoagulant therapy.

INTRODUCTION: Anticoagulants of the coumarin type are effective drugs for the treatment and prevention of thromboembolic diseases. However, they have a narrow therapeutic range and show inter- and intra-individual variability in dose requirement, largely conditioned by both environmental and genetic factors. METHODS: This prospective study investigated, during the initial phase of acenocoumarol therapy, the effect of CYP2C9 variant alleles and VKORC1 haplotypes, single and in combination, in 220 Italians. RESULTS: CYP2C9*3 was associated with a 25% dose reduction and an increased risk of over-anticoagulation (International Normalized Ratio [INR] > 6) on day 4. Two copies of the VKORC1*2 haplotype were associated with a 45% dose reduction and an increased risk of over-anticoagulation. Homozygosity for VKORC1*3 and VKORC1*4 was associated with an increased dose requirement and a reduced risk of over-anticoagulation. The VKORC1*3 or *4 plus CYP2C9*1 genotype combination was associated with the highest dose requirement and the lowest INR on day 4; VKORC1*2 plus CYP2C9*3 was associated with the lowest dose requirement, the highest INR and an increased risk of over-anticoagulation. Even though they spent approximately 50% of the time within the target therapeutic range, VKORC1*3 or *4 plus CYP2C9*1 carriers spent a large percentage of the remaining time below and carriers of VKORC1*2 plus CYP2C9*3 above the target range. DISCUSSION: The determination of VKORC1*3 and VKORC1*4 haplotypes may be an important addition to CYP2C9 and VKORC1*2 genotyping to identify patients at risk of being outside the target range during initial anticoagulation with acenocoumarol.