Update on selected inherited venous thrombotic disorders

Thrombophilia gene mutations predict venous thromboembolism in ambulatory cancer patients receiving chemotherapy

BACKGROUND

Inherited thrombophilia and cancer both independently increase the risk of venous thromboembolism (VTE). However, whether the increased VTE risk associated with inherited thrombophilia exists in cancer patients is less clear.

OBJECTIVES

Our objective was to determine the influence of inherited thrombophilia on VTE and bleeding risk in moderate-to-high-risk ambulatory cancer patients receiving chemotherapy.

METHODS

We conducted a post hoc analysis using blood samples from patients enrolled in the AVERT trial to determine if previously recognized thrombophilia gene mutations (prothrombin factor [F] II G20210A, FXI, fibrinogen gamma, serpin family A member 10, FV K858R, FXIII, FV Leiden [FVL], and ABO blood) were associated with VTE or bleeding during the 7-months after starting chemotherapy. Logistic regression was used to compare heterozygous and homozygous mutations (combined) to wild-type. VTE rates, bleeding rates, and risk differences for mutations stratified by prophylactic anticoagulation use were calculated.

RESULTS

Of the 447 patients, there were 39 VTE and 39 bleeding events. The odds of VTE were significantly increased with FVL mutation and non-O blood type (odds ratio [OR]: 5.2; 95% CI: 1.9-14.7 and OR: 2.7; 95% CI: 1.2-6.1, respectively). The use of anticoagulation prophylaxis resulted in complete protection in FVL patients, whereas those not receiving anticoagulation had a VTE rate of 119 per 100 patient-years. Lower VTE rates were also observed in non-O blood type patients taking prophylactic anticoagulation. No other thrombophilia genes tested were significantly associated with VTE or bleeding.

CONCLUSION

Our results indicate that FVL mutation and ABO blood type may be important VTE predictors in cancer patients starting chemotherapy.

Association between serum vitamin D levels and venous thromboembolism (VTE): A systematic review and meta-analysis of observational studies

OBJECTIVE

Although many studies have attempted to unravel the relationship between vitamin D deficiency and the incidence of VTE, the results remained inconsistent. To address this discrepancy, we performed a systematic review and meta-analysis to precisely disentangle the relationship between serum vitamin D levels and VTE risk.

METHODS

The Web of Science, Scopus, PubMed/Medline, Embase, and Google Scholar databases were searched for all available observational studies that reported the risk of venous thromboembolism (VTE) based on serum vitamin D levels categories. The search was performed up to March 2020.

RESULTS

Seven studies were included. The overall analysis showed a significantly increased risk of VTE in subjects with low levels of serum vitamin D compared with those with normal vitamin D levels (RR = 1.34; 95% CI: 1.07-1.69; P = 0.011). In a sensitivity analysis, we did not observe a significant effect of any individual study on the combined effect sizes. Nevertheless, significant heterogeneity was present among the studies (Cochrane Q test, p = 0.018, I² = 61%). In the stratified analysis, low vitamin D levels were positively associated with an increased risk of VTE in prospective population-based studies (RR = 1.31; 95% CI: 1.06-1.61; P = 0.010) and in subjects below 60 years old (RR = 1.28; 95% CI: 1.07-1.54; P = 0.060).

CONCLUSION

our systematic review and meta-analysis showed that a low serum vitamin D level was indeed associated with an increased risk of VTE.

The joint effect of genetic risk factors and different types of combined oral contraceptives on venous thrombosis risk

It is not known whether the synergistic effect of genetic markers, increasing the risk of venous thrombosis (VT), and combined oral contraceptives (COC) use varies between different types of progestogens in these preparations. We investigated the joint effect of genetic risk factor, that is, F5 rs6025, F2 rs1799963, and FGG rs2066865 mutations, and different progestogens on the risk of VT. The constrained maximum likelihood estimation (CMLE) method was used to calculate joint effects, expressed as odds ratio (OR) with 95% confidence intervals [CI]. As the dose of estrogen is known to be a risk factor for VT, analyses were restricted to COC with 30 µg estrogen and each progestogen. Overall, the joint effect of COC and genetic variants was lowest for COC containing the progestogen levonorgestrel, albeit CIs were wide. The OR (95% CI) of the four different analyses (i.e. joint effect with F5 rs6025, F2 rs1799963, F5 rs6025 or F2 rs1799963 and FGG rs2066865) ranged between 7·4 (5·4–10·2) and 24·8 (12·3–50·0) for levonorgestrel. For gestodene the joint effect ranged between 11·7 (7·2–19·1) and 30·9 (10·6–89·9). Desogestrel and cyproterone acetate had the highest risk estimates: 14·6 (9·7–21·9) and 32·6 (13·2–80·6) and 15·5 (9·7–24·9) and 44·4 (16·9–116·3) respectively. In women with inherited thrombophilia, COC containing levonorgestrel were associated with the lowest risk of VT, albeit the CIs were wide.

Risk factors for deep vein thrombosis of lower extremities in Sudanese women

Aim

In this study, we aimed to analyze the genetic and acquired risk factors for deep vein thrombosis (DVT) of the lower extremities among Sudanese women.

Methods

A total of 136 women were enrolled in the study, including 75 DVT patients and 61 healthy controls. Demographic and clinical data were collected using a specific questionnaire. Citrated blood samples of patients and controls were used for coagulation assays, and DNAs isolated from EDTA-blood samples were used for the detection of Factor V Leiden and prothrombin G20210A mutations using multiplex polymerase chain reaction-restriction fragment length polymorphism analysis.

Results

Both gene mutations were found to be absent from all 136 subjects, and therefore did not account for the incidence of DVT in Sudanese women. Of the 75 DVTs, 70 (93.3%) were localized in the left leg and 5 (6.7%) in the right leg. Additionally, 84% of the DVTs were proximal and 16% were distal. Among the 75 patients, 22 (29.33%) were postpartum, 7 (9.33%) were pregnant, and 46 (61.33%) were nonpregnant. Levels of prothrombin fragment 1+2, prothrombin time, activated partial thromboplastin time, and D-dimer were significantly higher in DVT patients than in healthy controls (P<0.0001).

Conclusion

Risk factors that most significantly affected patients in the 18–45 years age group were pregnancy and oral contraceptive usage, whereas those that most significantly affected patients in the 66–90 years age group were immobility, heart disease, and history of DVT.

Serum levels of vitamin D are not associated with future risk of venous thromboembolism

Previous studies have provided indirect evidence for a possible association between vitamin D status and risk of venous thromboembolism (VTE). However, no study has so far investigated the association between serum levels of 25-hydroxyvitamin D (25(OH)D), the biomarker of vitamin D status, and risk of VTE. The aim of our study was to investigate whether high levels of 25(OH)D were associated with decreased risk of VTE in a prospective population-based study. Serum levels of 25(OH)D were measured in 6,021 men and women, aged 25–84 years, who participated in the Tromsø Study in 1994–1995. Incident VTE-events were registered from date of inclusion through the end of follow-up, September 1, 2007. Cox-regression models were used to calculate hazard ratios (HR) with 95% confidence interval (CI) for VTE. There were 201 incident VTE-events during a median of 10.7 years of follow-up. The risk of VTE did not decrease per one standard deviation (SD) (19.8 nmol/l) increase in serum 25(OH)D (multivariable HR 1.02; 95% CI 0.91–1.22). Moreover, subjects with serum 25(OH)D ≥ 70 nmol/l (upper quartile) did not have decreased risk of VTE compared to those ≤ 44 nmol/l (lower quartile) in age- and sex-adjusted analysis (HR 0.91, 95% CI: 0.60–1.37, p for trend across quartiles 0.9) or multivariable analysis adjusted for age, sex, body mass index, smoking, and physical activity (HR 0.76, 95% CI: 0.45–1.28, p for trend across quartiles 0.9). Subgroup analyses showed no associations between serum levels of 25(OH)D and unprovoked or provoked VTE. In conclusion, in our study, normal serum levels of 25(OH)D were not associated with future risk of VTE, suggesting that vitamin D status does not play an important role in the pathogenesis of VTE. However, our findings did not apply to subjects with vitamin D deficiency (< 30 nmol/l) due to lack of statistical power among these subjects.

Associations between serum levels of calcium, parathyroid hormone and future risk of venous thromboembolism: the Tromsø study

OBJECTIVE

The relationship between serum levels of calcium, parathyroid hormone (PTH) and risk of venous thromboembolism (VTE) has not been addressed in population-based cohorts. We investigated the associations between serum levels of calcium and PTH, with future risk of VTE in a general adult population.

DESIGN

Population-based cohort.

METHODS

A total of 27 712 subjects (25-87 years) who participated in Tromsø 4 (1994-1995) and Tromsø 5 (2001-2002) surveys were included in the study, and total calcium and PTH were measured in 27 685 and 8547 subjects respectively. Incident VTE was recorded through December 31, 2012. Cox-regression models with calcium and PTH as time-varying exposures were used to calculate hazard ratios (HR) of VTE by quartiles of calcium and PTH. Quartiles of calcium and PTH were also combined to assess the effect of discordants of both PTH and calcium (e.g. highest and lowest quartiles of both calcium and PTH) on VTE risk using the middle two quartiles as reference.

RESULTS

There were 712 VTEs during 15.0 years of median follow-up. Serum levels of calcium and PTH were not associated with risk of VTE. However, subjects with discordant high serum levels of both calcium and PTH (calcium ≥2.45 mmol/L and PTH ≥4.0 pmol/L) had increased risk of VTE compared to those in subjects with normal calcium and PTH (multivariable HR: 1.78, 95% CI: 1.12-2.84).

CONCLUSIONS

Serum levels of calcium and PTH separately were not associated with future risk of VTE, but subjects with high levels of both calcium and PTH had increased risk of VTE compared to those in subjects with normal levels.

Clinical Trial of Erythropoietin in Young Children With Cerebral Palsy

This study was conducted to assess the safety and efficacy of recombinant human erythropoietin in young children with cerebral palsy aged between 6 months and 3 years. All participants received subcutaneous recombinant human erythropoietin and 8 weeks of rehabilitation therapy. Adverse events, changes of vital signs, and hematologic tests were monitored up to 8 weeks postinjection. Functional measures of development at 4 and 8 weeks postinjection were compared with baseline values, and improvements were compared with those of an age-matched historical control group. Nine participants completed the trial from June 2012 to February 2015. No adverse events were related to recombinant human erythropoietin. Erythropoiesis was noted, although within normal range. Functional improvements were observed in all participants (P < .05) and increases in motor function were higher in recombinant human erythropoietin group than the control group. Accordingly, recombinant human erythropoietin administration was safe without any significant adverse events and improved the functional outcomes in young children with cerebral palsy.

Thyroid function, as assessed by TSH, and future risk of venous thromboembolism: the Tromsø study

OBJECTIVE

The relationship between thyroid function and the risk of venous thromboembolism (VTE) has not been addressed in population-based cohorts. We investigated the association between TSH levels and the risk of VTE in a general adult population.

DESIGN

Population-based cohort study.

METHODS

TSH was measured in 11 962 subjects aged 25-89 years who participated in Tromsø 4-6 starting in 1994-1995. Incident VTE events were recorded through 31st December 2010. Cox's regression models with TSH as a time-varying covariate were used to calculate hazard ratios (HRs) of VTE by TSH categories (low TSH: <0.05  mU/l; moderately reduced TSH: 0.05-0.19  mU/l; normal TSH: 0.20-4.00  mU/l; moderately elevated TSH: 4.01-5.00  mU/l; and high TSH: >5.00 mU/l) and within the normal range of TSH, modeling TSH as a continuous variable.

RESULTS

There were 289 VTEs during 8.2 years of median follow-up. Subjects with low (prevalence: 0.22%) and high (3.01%) TSH had slightly higher risk estimates for VTE than did subjects with normal TSH (multivariable HRs: 2.16, 95% CI 0.69-6.76 and 1.55, 95% CI 0.87-2.77 respectively), but the CIs were wide. Moreover, there was no association between TSH within the normal range and VTE (HR per 1 mU/l increase: 0.95, 95% CI 0.82-1.11).

CONCLUSION

Serum levels of TSH within the normal range were not associated with a risk of VTE, whereas low and high TSH levels were rare and associated with a moderately higher risk of VTE. The present findings suggest that only a minor proportion of the VTE risk in the population can be attributed to thyroid dysfunction.

Hyperglycemia, assessed according to HbA1c , and future risk of venous thromboembolism: the Tromsø study

BACKGROUND

HbA1c , a marker of average plasma glucose level during the previous 8-12 weeks, is associated with the future risk of cardiovascular disease and all-cause mortality.

OBJECTIVES

To examine the association between hyperglycemia, assessed according to HbA1c , and the future risk of venous thromboembolism (VTE) in a population-based cohort.

METHODS

HbA1c was measured in 16 156 unique subjects (25-87 years) who participated in one or more surveys of the Tromsø study (Tromsø 4, 1994-1995; Tromsø 5, 2001-2002; and Tromsø 6, 2007-2008). All subjects were followed, and incident VTE events were recorded up to 31 December 2010.

RESULTS

There were 333 validated first VTE events, of which 137 were unprovoked, during a median follow-up of 7.1 years. HbA1c was not associated with the future risk of VTE in analyses treating HbA1c as a continuous variable, or in categorized analyses. The risk of VTE increased by 5% per one standard deviation (0.7%) increase in HbA1c (multivariable-adjusted hazard ratio [HR] 1.05; 95% confidence interval [CI] 0.97-1.14), and subjects with HbA1c  ≥ 6.5% had a 27% higher risk than those with HbA1c  < 5.7% (multivariable-adjusted HR 1.27; 95% CI 0.72-2.26). There was no significant linear trend for an increased risk of VTE across categories of HbA1c (P = 0.27).

CONCLUSIONS

Serum levels of HbA1c were not associated with the future risk of VTE in multivariable analysis. Our findings suggest that hyperglycemia does not play an important role in the pathogenesis of VTE.

Elevated factor IX activity is associated with an increased odds ratio for both arterial and venous thrombotic events

OBJECTIVES

Elevations of factor IX (FIX) are thought to contribute to thrombotic risk, but this has not been well characterized. We retrospectively sought to determine whether elevated FIX levels are a risk factor for thrombosis in 81 adult subjects younger than 65 years (mean, 47 years) who were referred for evaluation of a hypercoagulable state.

METHODS

Patients were classified by arterial transient ischemic attack/stroke (TIA/stroke, n = 62) or venous thromboembolism (VTE, n = 19) events. FIX activity testing was performed on all 81 subjects and a reference group of 40 healthy individuals.

RESULTS

Thirteen (21%) of 62 subjects with TIA/stroke and 5 (26%) of 19 subjects with VTE had elevated FIX activity. Odds ratios for TIA/stroke and VTE in subjects with elevated FIX activity were 3.7 (95% confidence interval [CI], 0.76-17.65) and 6.8 (95% CI, 1.18-39.07), respectively.

CONCLUSIONS

Our findings suggest an association between elevated FIX levels and both arterial and venous thrombotic events.

Platelet count and mean platelet volume in patients with in-hospital deep venous thrombosis

AIM

To investigate the relationship between mean platelet volume (MPV) and in-hospital deep venous thrombosis (DVT).

MATERIAL AND METHODS

147 patients with the diagnosis of DVT and 149 control participants were included in the study. For all participants, clinical risk factors, smoking status, and other demographic data were recorded from hospital registries. The data of patients with DVT were compared with the control participants.

RESULTS

Mean MPV was significantly higher in patients with DVT than the control group (8.91 ± 1.86 vs 7.86 ± 0.9; P < .001). Body mass index, smoking frequency, hematocrit, and platelet count were significantly correlated with MPV. Independent predictors of in-hospital DVT were MPV (odds ratio [OR] = 1.5; 95% confidence interval [CI] = 1.2-1.87; P ≤ .001), body mass index (OR = 1.17; 95% CI = 1.04-1.34; P = .012), and smoking (OR = 1.83; 95% CI = 1.09-3.08; P = .023).

CONCLUSION

Mean platelet volume was significantly higher in patients with DVT, and it is an independent predictor of in-hospital DVT.

Cystatin C is associated with risk of venous thromboembolism in subjects with normal kidney function--the Tromsø study

BACKGROUND

Previous studies have shown an association between impaired kidney function, assessed by cystatin C-based estimated glomerular filtration rate, and venous thromboembolism. The aim of this study was to investigate whether serum cystatin C was associated with a risk of venous thromboembolism among subjects with normal kidney function in a prospective population-based study.

DESIGN AND METHODS

Cystatin C was measured in serum from 3251 men and women with normal kidney function, aged 25-84 years, who participated in the Tromsø study in 1994-1995. Normal kidney function was defined as a creatinine-based estimated glomerular filtration rate greater than 90 mL/min/1.73 m(2) and absence of microalbuminuria. Incident venous thromboembolism was registered from the date of inclusion through to the end of follow-up, September 1, 2007. Cox-regression models were used to calculate hazard ratios with 95% confidence intervals for venous thromboembolism.

RESULTS

There were 83 incident venous thromboembolic events, of which 53 (63.9 %) were provoked, during a median of 12.3 years of follow-up. A one standard deviation (0.11 mg/L) increase in serum cystatin C levels was associated with a 43% (hazard ratio 1.43; 95% confidence interval 1.17-1.72) increased risk of total venous thromboembolism. Subjects with cystatin C levels in the top quartile (≥ 0.87 mg/L) had a 2.5-fold (hazard ratio 2.51; 95% confidence interval 1.27-4.96) increased risk of venous thromboembolism compared to those with levels in the bottom quartile (≤ 0.72 mg/L) in adjusted analysis. The risk estimates were even higher for provoked venous thromboembolism (hazard ratio 3.11; 95% confidence interval 1.23-7.86).

CONCLUSIONS

Serum cystatin C levels were associated with the risk of venous thromboembolism in subjects with normal kidney function. Our findings suggest that elevated serum cystatin C levels may promote venous thrombosis beyond reflecting impaired kidney function.

Thrombophilia in patients with chronic venous leg ulcers-a study on patients with or without post-thrombotic syndrome

BACKGROUND

Chronic venous leg ulcers (CVU) cause considerable burden of disease for the patients as well as enormous costs for health care systems. The pathophysiology of CVU is complex and not entirely understood. So far reliable pathogenic and/or prognostic parameters have not been identified.

OBJECTIVES

We studied the role of thrombophilia in patients referred to a University dermatology department for treatment of CVU.

PATIENTS AND METHODS

A cohort of 310 patients with active chronic venous leg ulcers (CEAP 6) was stratified into two comparably large groups according to the presence or absence of post-thrombotic syndrome (PTS+; PTS-) as determined using duplex scan and/or phlebography. In addition, several thrombophilia parameters were assessed.

RESULTS

The prevalence of protein S deficiency and factor V Leiden mutation was significantly higher in PTS+ patients compared with the PTS- group. However, patients in both subgroups revealed high prevalences of thrombophilia (antithrombin deficiency, protein C deficiency, protein S deficiency, activated protein C resistance, factor V mutation or elevated homocysteine).

CONCLUSION

Based on these data, it is conceivable that thrombophilia contributes to the pathogenesis of CVU, possibly through induction of microcirculatory dysregulations.

Diagnostic algorithm for thrombophilia screening

Thrombophilia screening is aimed at detecting the most frequent and well-defined causes of venous thrombosis, such as activated protein C resistance/factor V Leiden mutation, prothrombin G20210A gene mutation, deficiencies of natural anticoagulants, such as antithrombin, protein C and protein S, the presence of antiphospholipid antibodies, hyperhomocysteinemia and increased factor VIII activity. At this time, thrombophilia screening is not recommended for those possible congenital or acquired risk factors, whose association with increased risk of thrombosis has not been proven sufficiently. Laboratory investigations should include a step-wise approach to the diagnosis of thrombotic disorders with respect to the assays and methods of analysis that are used. The assays recommended for the first diagnostic step of screening should establish, whether the subject has one of the common causes of thrombophilia. If one or more abnormal results are obtained, the second diagnostic step includes the assays recommended for confirmation and/or characterization of the defect. When performing the investigation of thrombophilia, it is important to consider all pre-analytical and other variables that may affect the results of thrombophilia testing, including time of testing, age, gender, liver function, hormonal status, pregnancy or the acute phase response to inflammatory diseases. This is necessary, in order to avoid, any misinterpretation of the results. This review summarizes the current knowledge concerning thrombophilia investigations, with special focus on the diagnostic algorithm regarding patient selection, the assays and methods of analysis used and all the variables that should be considered when employing tests for the diagnosis of thrombophilia.

Physical activity and risk of venous thromboembolism. The Tromso study

BACKGROUND

Previous studies have shown differences in the impact of regular physical exercise on the risk of venous thromboembolism. The inconsistent findings may have depended on differences in study design and specific population cohorts (men only, women only and elderly). We conducted a prospective, population-based cohort to investigate the impact of regular physical exercise on the risk of venous thromboembolism.

DESIGN AND METHODS

Risk factors, including self-reported moderate intensity physical exercise during leisure time, were recorded for 26,490 people aged 25-97 years old, who participated in a population health survey, the Tromsø study, in 1994-95. Incident venous thromboembolic events were registered during the follow-up until September 1, 2007.

RESULTS

There were 460 validated incident venous thromboembolic events (1.61 per 1000 person-years) during a median of 12.5 years of follow-up. Age, body mass index, the proportion of daily smokers, total cholesterol, and serum triglycerides decreased (P<0.001), whereas high density cholesterol increased (P<0.001) across categories of more physical exercise. Regular physical exercise of moderate to high intensity during leisure time did not significantly affect the risk of venous thromboembolism in the general population. However, compared to inactivity, high amounts of physical exercise (≥ 3 hours/week) tended to increase the risk of provoked venous thromboembolism (multivariable hazard ratio, 1.30; 95% confidence interval, 0.84-2.0), and total venous thromboembolism in the elderly (multivariable hazard ratio, 1.33; 95% confidence interval, 0.80-2.21) and in the obese (multivariable hazard ratio, 1.49; 95% confidence interval, 0.63-3.50). Contrariwise, compared to inactivity, moderate physical activity (1.0-2.9 hours/week) was associated with a border-line significant decreased risk of venous thromboembolism among subjects under 60 years old (multivariable hazard ratio, 0.72; 95% confidence interval, 0.48-1.08) and subjects with a body mass index of less than 25 kg/m(2) (multivariable hazard ratio, 0.59; 95% confidence interval, 0.35-1.01).

CONCLUSIONS

Our study showed that regular, moderate intensity physical exercise did not have a significant impact on the risk of venous thromboembolism in a general population. Future studies are required to assess the impact of regular physical exercise on venous thromboembolism risk in different population subgroups.

Body height and risk of venous thromboembolism: The Tromsø Study

An association between body height and venous thromboembolism (VTE) has been suggested by previous studies including males only. The aim of this prospective cohort study was to investigate the sex-specific impact of body height on risk of VTE in a general population. Risk factors, including body height and weight, were registered for 26,727 subjects aged 25-96 years who participated in the Tromsø Study (Norway) in 1994-1995. Incident VTE events were registered through September 1, 2007. There were 462 VTE events during a median 12.5 years of follow-up. Body height was a risk factor for VTE in men, but not in women. Multivariable hazard ratios per 10 cm, adjusted for age, body mass index, diabetes, smoking, and hormone therapy (women), were 1.34 (95% confidence interval: 1.09, 1.64) for men and 1.13 (95% confidence interval: 0.91, 1.40) for women. Hazard ratios by quartiles of body height revealed that men in the upper quartile (>181 cm) had a 1.99-fold (95% confidence interval: 1.35, 2.92) increased risk of VTE compared with men in the lowest quartile (<173 cm) (P for trend across quartiles = 0.002). There was no significant trend (P = 0.2) across quartiles of body height for women. Study findings revealed that body height is a sex-specific risk factor for VTE in men.

Mean platelet volume is a risk factor for venous thromboembolism: the Tromsø Study, Tromsø, Norway

BACKGROUND

Platelet size, measured as mean platelet volume (MPV), is associated with platelet reactivity. MPV is increased in acute myocardial infarction, and has been identified as an independent risk factor for future myocardial infarction and stroke.

OBJECTIVES

The purpose of the study was to determine the impact of platelet count and MPV on the incidence of venous thromboembolism (VTE) in a prospective, population-based study.

METHODS

Platelet count, MPV and baseline characteristics were registered in 25 923 subjects aged 25-96 years who participated in the Tromsø Study in 1994-1995. Incident VTE events were registered to the end of follow-up (1 September 2007).

RESULTS

There were 445 validated incident VTE events (1.6 per 1000 person-years), of which 186 (42%) were unprovoked, during a mean of 10.8 years of follow-up. Subjects with MPV >or= 9.5 fL had a 1.3-fold [95% confidence interval (CI) 1.0-1.7] higher risk of total VTE and a 1.5-fold (95% CI 1.1-2.3) higher risk of unprovoked VTE than subjects with MPV < 8.5 fL in analyses adjusted for age, sex, smoking, body mass index, and platelet count. Increasing MPV was associated with increased risk of total VTE (P for trend = 0.09) and unprovoked VTE (P for trend = 0.03) in analyses adjusted for age and sex. There was no significant association between increasing platelet count and risk of VTE.

CONCLUSIONS

An increasing MPV was identified as a predictor for VTE, in particular VTE of unprovoked origin. The present findings support the concept that platelet reactivity is important in the pathogenesis of VTE.

Inherited Thrombophilia

Inherited thrombophilia can be defined as a genetically determined predisposition to the development of thromboembolic complications. Since the discovery of activated protein C resistance in 1993, several additional disorders have been described and, at present, it is possible to identify an inherited predisposition in about 60 to 70% of patients with such complications. These inherited prothrombotic risk factors include qualitative or quantitative defects of coagulation factor inhibitors, increased levels or function of coagulation factors, defects of the fibrinolytic system, altered platelet function, and hyperhomocysteinemia. In this review, the main inherited prothrombotic risk factors are analyzed from epidemiological, laboratory, clinical, and therapeutic points of view. Finally, we discuss the synergism between genetic and acquired prothrombotic risk factors in particular conditions such as childhood and pregnancy.

Testing for hereditary thrombophilia: a retrospective analysis of testing referred to a national laboratory

Background

Predisposition to venous thrombosis may be assessed through testing for defects and/or deficiencies of a number of hereditary factors. There is potential for confusion about which of these tests are appropriate in which settings. At least one set of recommendations has been published to guide such testing, but it is unclear how widely these have been disseminated.

Methods

We performed a retrospective analysis of laboratory orders and results at a national referral laboratory to gain insight into physicians' ordering practices, specifically comparing them against the ordering practices recommended by a 2002 College of American Pathologists (CAP) consensus conference on thrombophilia testing. Measurements included absolute and relative ordering volumes and positivity rates from approximately 200,000 thrombophilia tests performed from September 2005 through August 2006 at a national reference laboratory. Quality control data were used to estimate the proportion of samples that may have been affected by anticoagulant therapy. A sample of ordering laboratories was surveyed in order to assess potential measurement bias.

Results

Total antigen assays for protein C, protein S and antithrombin were ordered almost as frequently as functional assays for these analytes. The DNA test for factor V Leiden was ordered much more often than the corresponding functional assay. In addition, relative positivity rates coupled with elevations in prothrombin time (PT) in many of these patients suggest that these tests are often ordered in the setting of oral anticoagulant therapy.

Conclusion

In this real-world setting, testing for inherited thrombophilia is frequently at odds with the recommendations of the CAP consensus conference. There is a need for wider dissemination of concise thrombophilia testing guidelines.

Inherited thrombophilia is associated with deep vein thrombosis in a Colombian population

The development of venous thromboembolism is influenced by a variety of genetic and environmental risk factors. A few studies have ascertained whether thrombophilic defects are risk factors for venous thromboembolism in Latin American populations with a variable degree of admixture, such as the Colombian population. To address this issue, we conducted a case-control study involving 100 consecutive patients with deep vein thrombosis and 114 healthy controls from the Hospital Universitario San Vicente de Paúl, Medellín, Colombia. Activated protein C resistance (APC resistance) was detected in 25/99 patients vs. 6/114 controls (OR = 6.08, 95% CI = 2.23-17.47). Ten of 100 patients carried the factor V Leiden mutation vs. 1/114 controls (OR = 12.56, 95% CI = 1.61-267). APC resistance was associated with the factor V Leiden mutation in only 10/25 patients. The prothrombin G20210A mutation was found in 4/100 patients, but none of the controls (P < 0.05). There was no significant difference in the proportion of homozygous carriers of methylenetetrahydrofolate reductase C677T variant among patients and controls. In conclusion, in our studied population, factor V Leiden, APC resistance, and prothrombin G20210A were associated with an increased risk of deep vein thrombosis. However, the frequencies of these thrombophilic defects and of APC resistance associated with factor V Leiden was lower than the corresponding frequencies previously reported for Caucasian populations. Further study is required to assess the influence of ethnicity on thrombophilia.

[Mechanisms of action of recombinant human activated Protein C]

Human activated protein C (APC) is a serineprotease and one of the most important physiological inhibitors of the coagulation system. Apart from anticoagulative effects, profibrinolytic and anti-inflammatory modes of action have been reported for APC. The administration of recombinant human activated protein C (rhAPC), drotrecogin alfa (activated), Xigris, to patients with severe sepsis and sepsis-induced multi-organ failure reduced mortality in large clinical trials. Anti-apoptotic and immunomodulatory effects of rhAPC have been examined in in vitro experiments and in experimental animal studies. Moreover, a reduction of endothelial cell permeability, enhanced endothelial cell survival as well as improvements of microcirculatory disorders have been proposed for rhAPC. The manifold mechanisms of action of APC may give reasons for its application in diseases other than sepsis, which are characterized by endothelial and microcirculatory dysfunction, e.g. acute pulmonary or renal failure, ischemic stroke, ischemia-reperfusion injury and acute pancreatitis. A better understanding of the anti-inflammatory, anti-apoptotic and immunomodulatory modes of action of APC could be relevant for dosing and mode of application and may lead to a broadening of the indication field for rhAPC.

Subclinical atherosclerosis and the risk of future venous thrombosis in the Cardiovascular Health Study

BACKGROUND

Recent reports have suggested an association of atherosclerosis with risk of venous thrombosis.

OBJECTIVE

To confirm whether subclinical atherosclerosis is a risk factor for venous thrombosis (VT) among men and women age 65 and older.

METHODS

Participants of the Cardiovascular Health Study (n = 4,108) without baseline clinical cardiovascular disease, anticoagulant use or previous VT were followed for a median of 11.7 years after non-invasive assessment of subclinical atherosclerosis using carotid ultrasound (intima-media thickness and presence of plaques), ankle-brachial blood pressure index and electrocardiogram. Each event was classified as idiopathic or secondary. We used Cox proportional hazards regression to estimate the relative risk of overall and idiopathic VT for individuals with and without baseline subclinical atherosclerosis.

RESULTS

There were 133 first time VT events. No subclinical atherosclerosis measures were associated with increased risk of overall or idiopathic VT. The adjusted relative risks of overall and idiopathic VT for presence of any type of subclinical disease were 0.60 (95% confidence interval 0.39-0.91) and 0.32 (0.18-0.59), respectively. Most of this association was explained by an inverse association of high-risk carotid plaques (prevalent in 54% of those at risk) with VT.

CONCLUSION

Non-invasively measured subclinical atherosclerosis was not associated with increased risk of overall or idiopathic VT in this observational study. Carotid plaques and arterial events during follow up were inversely associated, a finding that requires further study.

Elevated coagulation factor VIII, postoperative thrombosis and flap failure in late breast reconstruction with a free TRAM flap: a case report

Only a few studies have sought to establish whether an underlying coagulation disorder might predispose a patient to thrombosis or coincide with flap failure in the context of free flap surgery. Here, we report a case of both intra- and postoperative arterial anastomotic thromboses and late flap failure due to venous thrombosis after late breast reconstruction with a TRAM flap, in which laboratory evaluation revealed elevated levels of coagulation factor VIII (FVIII). High FVIII concentrations have recently been cited as an independent and dose-dependent risk factor for thromboembolism.

High plasma levels of factor VIII: An important risk factor for isolated pulmonary embolism

OBJECTIVE

The aim of the study was to investigate whether factor V Leiden and prothrombin G20210A mutations, elevated levels of factor VIII and factor IX are associated with pulmonary embolism (PE).

METHODS

Sixty-four patients with objectively documented PE and 64 control subjects were included in this study. The authors divided the 64 subjects with PE into those with PE and deep vein thrombosis (combined form of venous thromboembolism, n = 26) and those with PE without deep vein thrombosis (isolated PE n = 38).

RESULTS

There was no significant difference between the PE groups and the control subjects with regard to the presence of factor V Leiden and prothrombin mutations and elevated levels of factor IX. Using the 90th percentile measured in control subjects (P(90) = 168 U/dL) as a cut-off point for factor VIII levels, the authors found an 11-fold increased risk for both isolated PE patients and patients with a combined form of venous thromboembolism who have factor VIII levels >168 U/dL compared with individuals having factor VIII levels below this cut-off point. The risk was not affected by adjustments for other possible risk factors.

CONCLUSIONS

Elevated plasma factor VIII levels were found to be a significant, independent risk factor for PE.

Zebrafish: a genetic model for hemostasis and thrombosis

Here we review the zebrafish hemostatic system, its relevance to mammalian hemostasis, and its efficacy as a vertebrate genetic model to further the understanding of hemostasis and thrombosis.

Analysis of pediatric thrombotic patients in Turkey

This study analyzes the data of thrombotic children who were followed up in different pediatric referral centers of Turkey, to obtain more general data on the diagnosis, risk factors, management, and outcome of thrombosis in Turkish children. A simple two-page questionnaire was distributed among contact people from each center to standardize data collection. Thirteen pediatric referral centers responded to the invitation and the total number of cases was 271. All children were diagnosed with thromboembolic disease between January 1995 and October 2001. Median age at time of first thrombotic event was 7.0 years. Of the children 4% of the cases were neonates, 12% were infants less than 1 year old, and 17% were adolescents. Thromboembolic event was mostly located in the cerebral vascular system (32%), deep venous system of the limbs, femoral and iliac veins (24%), portal veins (10%), and intracardiac region (9%). Acquired risk factors were present in 86% of the children. Infection was the most common underlying risk factor. Inherited risk factors were present in 30% of the children. FVL was the most common inherited risk factor. Acquired and inherited risk factors were present simultaneously in 19% of the patients. Eleven children had a history of familial thrombosis. Due to the local treatment preferences, the treatment of the children varied greatly. Outcome of the 142 patients (52%) was reported: 88 (62%) patients had complete resolution, 47 (33%) had complications, 12 (9%) had recurrent thrombosis, and 34 (24%) died. Three children (2.1%) died as a direct consequence of their thromboembolic disease. The significant morbidity and mortality found in this study supports the need for multicentric prospective clinical trials to obtain more generalizable data on management and outcome of thrombosis in Turkish children.

The inherited thrombophilias: genetics, epidemiology, and laboratory evaluation

It is now possible to identify a predisposing thrombophilic condition for venous thrombosis in well over half of the cases. Certain thrombophilia diagnoses have a major impact on anticoagulant therapy, and hence it is incumbent upon physicians to understand how to diagnose and manage these conditions. This chapter covers the genetics and epidemiology of the inherited thrombophilias and provides a useful, common-sense approach to the laboratory evaluation of a patient with venous thrombosis.

Genetic analysis of hemostasis and thrombosis using vascular occlusion

The zebrafish is an excellent model for mammalian hemostasis and thrombosis since it possesses coagulation factors, thrombocyte receptors and responds to anti-coagulant and anti-platelet drugs commonly used in clinical treatment. In this study, exposure of larvae to FeCl(3) or laser irradiation produced a vessel injury that caused a visible vascular occlusion as a result of thrombus formation. Using the time to vascular occlusion as an assay, two screening strategies were tested for their utility in identifying novel genes involved in thrombosis. Morpholino knockdown studies of zebrafish factor VII showed a prolongation of the time to occlusion of the vessel whereas knockdown of the recently discovered factor VIIi resulted in a shortening of the time. Genetic screening of a population of zebrafish identified mutants that showed a prolongation of the time to occlusion. Bulk segregant analysis showed linkage of one mutant to a locus, victoria, on linkage group 7. Thus, the vascular occlusion assay developed in this report measures in vivo thrombus formation and is a powerful tool for identifying novel genes involved in thrombosis.

Prevalence of the 20210 G-->A prothrombin variant and its association with coronary artery disease in a Middle Eastern Arab population

BACKGROUND

No reports are available on the distribution of the 20210 G-->A prothrombin variant among Middle Eastern Arabs. Additionally, to date, studies that attempt to establish this polymorphism as an independent risk factor or as a predictor for coronary artery disease (CAD) have yielded conflicting results.

OBJECTIVE

To determine the prevalence of the 20210 G-->A prothrombin variant among Middle Eastern Arabs and to evaluate the potential relevance of this variant to Arab patients with angiographically documented CAD.

METHODS AND RESULTS

We used the polymerase chain reaction and restriction enzyme digestion to determine the prevalence of this polymorphism in 613 individuals from Arabic ethnic origin with CAD and from 593 healthy blood donors (BDs) from an identical ethnic background. Within the BD group (n = 593), 10 individuals (1.7%) were heterozygous, 583 individuals (98.3%) were normal, and none were homozygous for the 20210 G-->A prothrombin variant. Within the CAD group (n = 613), 13 individuals (2.1%) were heterozygous, 600 individuals (97.9%) were normal, and none were homozygous for the 20210 G-->A prothrombin variant. A chi(2) analysis was used to evaluate any significance in the distribution of genotypes. A value of 1.23 was obtained. Values less than 3.84 indicate no statistically significant difference between the heterozygous carriers of the 20210A allele in both study groups.

CONCLUSIONS

In our population of Middle Eastern Arabs, the presence of the 20210 G-->A prothrombin variant is not associated with patients with angiographically documented CAD. Therefore, this variant cannot be considered as an independent risk factor or as a predictor for CAD in this population.

Risk factors for thromboembolism in teens: when should I test?

The discoveries of the factor V Leiden mutation and the prothrombin gene variant 20210 in the last decade have markedly contributed to the understanding of the molecular pathophysiology of inherited risk factors for thrombophilia. Population studies in the adult literature have shown that although the overall prevalence of these defects is low, affected individuals are at increased risk of thrombosis particularly if acquired risk factors for thrombosis are also present. The use of combined hormonal oral contraceptive pills is a well-known acquired risk factor, and recent studies have shown significant increased risk of thrombosis for women who carry the factor V Leiden mutation and use oral contraceptive pills. Despite this significant increased risk, mass screening of asymptomatic women for factor V Leiden prior to prescribing oral contraceptive pills is not a cost-effective use of health care dollars and could result in unnecessarily preventing many women from the contraceptive and noncontraceptive benefits of this medication. Instead, clinicians can use thoughtful screening questions to identify potentially high-risk patients for thrombophilia and consider testing for inherited risk factors on a case-specific basis.