The investigation and management of inherited thrombophilia

Multivessel Thromboembolism Associated with Dysfunction of Protein S

Protein S is a vitamin K-dependent coagulation factor that acts as an anticoagulant. Deficiency of protein S increases the risk of thromboembolic events. We report a case of isolated protein S deficiency in a 39-year-old woman suffering arterial occlusion in both lower legs. She underwent a surgical procedure using thrombectomy and balloon angioplasty of her left lower extremity. Later, she had right trans-tibial amputation because of the reperfusion injury. Throughout the evaluation of thromboembolic events, we diagnosed a large thrombus in the right atrium and an asymptomatic pulmonary thromboembolism. The patient was successfully treated with right atrial thrombectomy and systemic anticoagulation. Careful evaluation for protein S levels may be necessary in patients with arterial thromboembolic events, especially young adults.

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.

Normal levels of protein C and protein S tested in the acute phase of a venous thromboembolic event are not falsely elevated

Background

Protein C (PC) and protein S (PS) determination is part of the thrombophilia investigation in patients with idiopathic venous thromboembolism (VTE). Based on scarce evidence it is a common notion that PC and PS levels decrease during the acute phase of VTE, necessitating delay of testing and temporary transition from warfarin to low molecular weight heparin. We have previously demonstrated that an abnormal PC or PS result determined within 24 hours of VTE diagnosis and before the initiation of warfarin needs to be repeated for confirmation ≥3 months after starting treatment and ≥14 days after stopping anticoagulation therapy. In the current study, we sought to show that normal PC and PS values determined during the acute phase of VTE are not false negatives.

Methods

99 patients with acute idiopathic VTE who had normal PC and PS determination within the first 24 hours of presentation and who subsequently had their oral anticoagulation discontinued after six months of therapy. PC and PS determinations were repeated ≥6 months after starting treatment and ≥ 14 days after stopping warfarin. Proportions of patients who tested abnormal on the second test were calculated and 95% confidence intervals obtained using the Wilson's score method. Data from a previously published study on patients with abnormal initial tests was included for comparison.

Results

None of the 99 patients who had normal PC and PS initially had an abnormal result on repeated testing (0%; 95% CI 0 - 3.7%). Data from the previous study showed that, among patients who initially had abnormal results, 40% (95%CI 35.4-84.8%) were confirmed to have low PC and 63.6% (95%CI 16.8-68.7%) low PS on repeated testing. The difference between proportions was statistically significant (χ² p-value < 0.001).

Conclusion

Our results suggest that PC and PS can be determined during the acute phase of VTE and whereas abnormal results need to be confirmed with repeat testing at a later date, a normal result effectively rules out deficiency with only one test.

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.

Determinants and associations of homocysteine and prothrombotic risk factors in Kuwaiti patients with cerebrovascular accident

OBJECTIVE

The objective of this study was to evaluate the determinants and associations of some prothrombotic risk factors in patients with cerebrovascular accidents (CVAs).

SUBJECTS AND METHODS

In this case-control study, plasma total homocysteine (tHcy), lupus anticoagulant, protein C, protein S, activated protein C resistance (APC-R) and antithrombin were measured in 102 patients (60 males and 42 females) and 167 controls (87 males, 80 females). Serum vitamin B(12), folate, red cell folate, creatinine, lipid profile and glucose were also determined. Glomerular filtration rate (GFR) was calculated.

RESULTS

13 (22%) of the 60 male patients, and 16 (39%) of the 42 female patients had hyperhomocysteinemia. Median (interquartile range) tHcy was higher in male patients [11.22 micromol/l (9.60-15.40)] than female patients [10.05 micromol/l (8.72-17.54)]. On binary logistic regression analysis, the significant (p < 0.05) determinants of tHcy were urea, creatinine and GFR. Comparing patients with control subjects showed that tHcy, age, fasting glucose, urea, serum creatinine, white blood cell count, protein S, APC-R and factor VIII were significantly higher, while protein C, factor II, total cholesterol, high-density lipoprotein cholesterol and low-density lipoprotein cholesterol were significantly lower in patients. Lupus anticoagulant was not associated with tHcy and not detected in patients and controls. Low concentrations of vitamins B(12) and folate were not associated with tHcy. Logistic regression analysis showed a significant association of tHcy with CVA (OR = 9.55; p = 0.047) in males in the presence of other traditional CVA risk factors but tHcy is not independently associated with CVA in females.

CONCLUSION

Hyperhomocysteinemia is common in Kuwaiti patients with CVA and tHcy probably interacts with prothrombotic factors (protein C, APC-R and factor VIII) to increase CVA risk. The main determinants, age and GFR markers, should be kept in mind when determining the risk associated with tHcy.

Plasma homocysteine and hematological factors in patients with venous thromboembolic diseases in Kuwait

BACKGROUND

Venous thromboembolic disease (VTE) is a common cause of morbidity in Kuwait, but the risk factors have not been studied. Hyperhomocysteinemia has been suggested as one of the risk factors. We postulate that hyperhomocysteinemia acts synergistically with hematological variables to increase VTE risk. This study evaluates the roles of hyperhomocysteinemia and hematological variables in patients with VTE.

METHODS

We measured fasting plasma total homocysteine (tHcy), activated protein C resistance, protein C (PC), protein S (PS) and antithrombin (AT) in 201 patients with VTE and 166 healthy controls. We also measured factor VIII, factor II, lupus anticoagulant, anticardiolipin, serum vitamin B12, folate, creatinine, lipid profile, glucose, full blood count and red cell folate. The glomerular filtration rate (GFR) was calculated from creatinine.

RESULTS

When patients on warfarin were excluded, 13.1% of patients (18 out of 137) had a deficiency in PC, 16.8% (23 out of 137) had a deficiency in PS, and when patients on heparin were excluded, 8.3% of patients (14 out of 168) had low AT. Spearman's rank correlation analysis showed that tHcy had significant correlations with age, creatinine and PS, and significant inverse correlations with GFR, high-density lipoprotein cholesterol and serum folate. Partial correlation analysis after correcting for age and sex showed that tHcy retained a significant correlation with creatinine, GFR and serum folate. Binary logistic regression analyses of the determinants of hyperhomocysteinemia included age, creatinine, GFR and serum folate. Multivariate logistic regression analysis showed significant association of tHcy with VTE (OR = 5.6; p < 0.0001) in the presence of known risk factors for VTE.

CONCLUSION

We conclude that elevated tHcy is a significant risk factor for the development of VTE, and therefore, it should be included in the workup for patients at risk of VTE, but the determinants of tHcy should be kept in mind.

Determinants of plasma homocysteine in relation to hematological and biochemical variables in patients with acute myocardial infarction

BACKGROUND

Elevated plasma total homocysteine (tHcy) is a risk factor for coronary artery disease (CAD), but the mechanism is not known. This study evaluates the determinants and associations of tHcy in patients presenting with acute myocardial infarction (AMI).

METHODS

Plasma concentration of tHcy, protein C, protein S, and antithrombin were measured in 210 (177 males and 33 females) patients with first AMI and 167 (87 males and 80 females) controls. Serum vitamin B12, folate, creatinine, lipid profile, fasting glucose, full blood count and red cell folate were determined. Creatinine clearance was calculated using the modification of diet in renal disease formula. Univariate and multivariate analyses were used to determine the associations of tHcy.

RESULTS

Mean tHcy was higher in male than female patients. On logistic regression analysis, the most important determinants oftHcy in the patients were age, creatinine, creatinine clearance, vitamin B12 and red cell folate. When study patients were compared with the controls, tHcy, fasting glucose and serum creatinine were significantly higher, while creatinine clearance and HDL cholesterol were significantly lower in the study patients. Logistic regression analysis showed significant association of tHcy with AMI, odds ratio = 1.39, in the presence of other confounding factors.

CONCLUSIONS

Our results show that tHcy is a significant risk factor for CAD in our patient population. The determinants in the patients are age, glomerular filtration rate and the status of vitamins B12 and folate. The above determinants should be kept in mind when using tHcy as a risk factor for CAD.

Protein C and protein S levels can be accurately determined within 24 hours of diagnosis of acute venous thromboembolism

In the 50% of cases of acute idiopathic venous thromboembolism, laboratory testing for inherited causes is often performed. Most physicians are under the impression that assays for protein C and protein S should not be measured at the time of diagnosis because of a high false positive rate. We performed a prospective cohort study from two outpatient thromboembolism clinics on consecutive patients with an objectively confirmed diagnosis of first acute idiopathic venous thromboembolism. Assays for protein C and protein S were performed prior to the initiation of oral anticoagulation therapy and within 24 h of diagnosis of venous thromboembolism. Abnormal results were repeated when patients discontinued oral anticoagulant therapy. Of 253 patients tested for both protein C and protein S, 229 (91%; 95% confidence interval 87-94%) were negative and 484 of 508 (95%) tests were normal. Of the 24 initial abnormal results, 21 were repeated and 10 (48%; 95% confidence interval 26-70%) were still abnormal. Overall, 97.8% of initial protein C and protein S results were accurate. If protein C and protein S are measured at the time of diagnosis of acute venous thromboembolism, the majority of the results will be normal and false positives are uncommon.

Primary thrombophilia in Mexico. V. A comprehensive prospective study indicates that most cases are multifactorial

Over a 36-month period, 46 consecutive Mexican mestizos with a clinical marker associated with a primary hypercoagulable state were prospectively assessed by searching for the sticky platelet syndrome (SPS), the activated protein C resistance (aPCR) phenotype, coagulation protein C activity and antigen, coagulation protein S, antithrombin III, plasminogen, tissue-type plasminogen activator activity, plasminogen activator inhibitor activity, plasminogen activator inhibitor type 1, IgG and IgM isotypes of antiphospholipid antibodies, homocysteine levels, the factor V gene Leiden, Cambridge, Hong Kong, and Liverpool mutations, the 677 C-->T mutation in the 5,10-methylenetetrahydrofolatereductase (MTHFR), and the G20210A polymorphism in the 3'-untranslated region of the prothrombin gene. Of the 46 consecutive patients prospectively accrued in the study, only 12 (26%) were males, the median age being 38 years (range 10-63 years). In only four individuals (8%) could we not record any abnormality. In 5/42 patients with abnormal results (12%), a single abnormality was recorded, whereas in the remaining 37, two to five co-existing abnormalities were identified. We found 22 (48%) patients with the SPS, 11 (24%) with the aPCR phenotype, 5 (11%) with the factor V Leiden mutation, 7 (15%) with the prothrombin gene mutation, 29 (63%) with the MTHFR gene mutation, 11 (24%) with the factor V HR2 haplotype, 11 (24%) with antiphospholipid antibodies, 4 (9%) with PS deficiency, 6 (13%) with PC deficiency, one with the FV Hong Kong mutation, and one with AT-III deficiency. The results are consonant with the idea that most cases of thrombophilia in Mexico are multifactorial.

Venous thromboembolism in the intensive care unit

Most ICU patients have a significant number of risk factors for VTE. The high incidence of DVT in the ICU population and the recognition of a high incidence of PE at autopsy confirm this. We have alluded to the difficulty of clinical diagnosis of VTE and the need for diagnostic investigations. We have reviewed currently available diagnostic investigations with regard to their sensitivity and specificity and their practicability in ICU patients, and have formulated recommended diagnostic algorithms (Figs. 4 and 5). The most important factor in the management of VTE is prevention. In the ICU, all patients are at high risk for VTE, and therefore, at a minimum should receive subcutaneous prophylactic heparin unless it is contraindicated. Alternative methods of prophylaxis are available, and should be considered for patients who have contraindications to heparin.

Thrombophilia and chronic venous ulceration

It is known that thrombophilia (TP) is a risk factor for deep venous thrombosis (DVT), and that DVT predisposes to chronic venous ulceration (CVU). However, the relationship between TP and CVU has not been well studied. Review of the literature reveals that the prevalence of TP in CVU patients is high--similar to the prevalence found in patients with a history of DVT. This is despite many patients with CVU having no clear history, or duplex evidence of previous DVT. TP may predispose to CVU by leading to macro- or micro-vascular thrombosis. This association raises several issues regarding the investigation, prevention and management of patients with venous disease.

Primary thrombophilia in Mexico III: A prospective study of the sticky platelet syndrome

During an 18-month period, 10 consecutive Mexican mestizos with a dinical marker associated with a primary hypercoagulable state were studied. The assessment of the sticky platelet syndrome (SPS) was done by the method described by Mammen. In addition, the activated protein C resistance phenotype, coagulation protein C activity and antigen, coagulation protein S, antithrombin III, plasminogen, tissue-type plasminogen activator activity, plasminogen activator inhibitor activity, plasminogen activator inhibitor type 1, IgG and IgM isotypes of anti-phospholipid antibodies, homocysteine levels, the factor V gene Leiden mutation, the 677 C->T mutation in the 5,10-methylen-tetrahydrofolate-reductase (MTHFR), and the G20210A polymorphism in the 3'-untranslated region of the prothrombin gene were studied. Six patients with the SPS were identified: only one displayed this as the single thrombophilic abnormality; in five others, additional thrombosis-prone conditions were found: heterozygosity for the MTHFR 677 gene mutation in five cases; and, in one case each, heterozygosity for the factor V Leiden mutation, heterozygosity for the factor II G20210A mutation, and antiphospholipid antibodies in another. Four of the six patients had a family history of thrombophilia. All patients were treated with aspirin and no new vasoocclusive episodes have been recorded. SPS in not an infrequent finding in Mexican mestizo thrombophilic patients and may contribute to thrombophilia.

Primary thrombophilia in Mexico. II. Factor V G1691A (Leiden), prothrombin G20210A, and methylenetetrahydrofolate reductase C677T polymorphism in thrombophilic Mexican mestizos

We have shown that in Mexican mestizo patients with clinical features of primary thrombophilia, 39% have activated protein C resistance phenotype, 5% protein C deficiency, and 2% protein S deficiency. In the present study, in a group of 37 thrombophilic Mexicans and 50 normal controls, we assessed the factor V G1691A (Leiden), the prothrombin G20210A, and the methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphisms. Four patients were found to be heterozygous for factor V Leiden, 5 heterozygous for the prothrombin 20210, 16 heterozygous, and 6 homozygous for the MTHFR 677. There were four individuals with co-segregation of alleles: two heterozygotes for the factor V Leiden/prothrombin 20210, one heterozygote for prothrombin 20210/MTHFR 677, and one heterozygote for prothrombin 20210/homozygote for MTHFR 677. For factor V Leiden, prothrombin 20210, and MTHFR 677 mutations, the allele frequencies were respectively 1% (+/-0.2%, alpha = 0.05), <1% and 51% (+/-5%, alpha = 0.05), with calculated relative risks for thrombosis of 5.94 (P = 0.08), >7.66 (P < 0.05), and 0.44 (P NS), respectively. In Mexican mestizo thrombophilic patients, the low prevalence of the factor V Leiden mutation (10.8%) and the high prevalence of the prothrombin 20210 mutation (13.5%) contrast with those identified in Caucasian thrombophilic patients (21% and 6%, respectively; P < 0.01). On the other hand, the high prevalence of the MTHFR 677 mutation gene both in normal controls (78%) and thrombophilic patients (61%) does not support a role of this mutation in the thrombogenesis of Mexican mestizo patients.