R. C. Tait

Prevalence of antithrombin deficiency in the healthy population

. In a cohort of 9669 blood donors we have identified 16 cases of congenital AT deficiency (1 in 600) by way of family studies and AT gene analysis. Two donors had type I AT deficiency (prevalence 0.21 per 1000; 95% CI = 0.03/1000 to 0.75/1000), their families displaying a symptomatic phenotype. 14 donors had a type II deficiency (prevalence 1.45 per 1000; 95% CI = 0.79/1000 to 2.43/1000): one recurring and three unique mutations. None of these type II deficiencies appeared to confer a high thrombotic risk despite many of the affected individuals having experienced potentially prothrombotic challenges. The high frequency of these relatively asymptomatic variants may reflect a selection bias in the study population. However, their existence should not only add to our understanding of structure‐function relationships of AT but may also influence our management of asymptomatic deficient individuals identified in epidemiological or presurgical screening programmes.

Clinical guidelines for testing for heritable thrombophilia

Trevor Baglin, Elaine Gray, Mike Greaves, Beverley J. Hunt, David Keeling, Sam Machin, Ian Mackie, Mike Makris, Tim Nokes, David Perry, R. C. Tait, Isobel Walker and Henry Watson Addenbrooke’s Hospital, Cambridge, NIBSC, South Mimms, University of Aberdeen, Aberdeen, Guy’s and St Thomas’, London, Churchill Hospital, Oxford, University College Hospital, London, Royal Hallamshire Hospital, Sheffield, Derriford Hospital, Plymouth, Glasgow Royal Infirmary, Glasgow and Aberdeen Royal Infirmary, UK

A study of Protein S antigen levels in 3788 healthy volunteers: influence of age, sex and hormone use, and estimate for prevalence of deficiency state.

Total Protein S (tPS) and free Protein S (fPS) antigen levels were measured in 3788 healthy blood donors. Men had higher levels of both parameters than women (P < 0·001). Age had no effect on tPS in men, although there was a slight reduction in fPS levels with increasing age. In women increasing age was associated with a significant increase in tPS levels (P < 0·001) but had no effect on fPS after adjustment for menopausal state. Oral contraceptive pill (OCP) use significantly lowered tPS but had no effect on fPS. In post‐menopausal women, hormone replacement therapy (HRT) use had no statistically significant effect on either tPS or fPS. Donors with tPS or fPS levels in the lowest percentile (n = 56) were retested; only nine with repeat low levels were identified, eight of whom had persistently low levels over a 4–7‐year follow‐up. Acquired deficiency was excluded. When possible, family studies were performed, leading to an estimate of prevalence of familial PS deficiency of between 0·03% and 0·13% in the general population.

The diagnosis and management of von Willebrand disease: a United Kingdom Haemophilia Centre Doctors Organization guideline approved by the British Committee for Standards in Haematology

The guideline group was selected to be representative of UKbased medical experts. MEDLINE and EMBASE were searched systematically for publications in English from 2002 using the key word Willebrand. The writing group produced the draft guideline, which was subsequently reviewed by the A United Kingdom Haemophilia Centre Doctors Organization (UKHCDO) advisory committee, a British Committee for Standards in Haematology (BCSH) sounding board of approximately 50 UK haematologists, and the BCSH executive; comments were incorporated where appropriate. The ‘GRADE’ system was used to quote levels and grades of evidence, details of which can be found in at http://www.bcshguidelines.com/BCSH_PROCESS/EVIDENCE_LEVELS_AND_ GRADES_OF_RECOMMENDATION/43_GRADE.html. The objective of this guideline is to provide healthcare professionals with clear guidance on the diagnosis and management of patients with von Willebrand disease.

Prothrombin 20210 G→A, MTHFR C677T mutations in women with venous thromboembolism associated with pregnancy

Over 50 unselected women with maternal venous thromboembolism were screened for the prothrombin 20210 G→A and MTHFR C677T mutations, in addition to screening for other thrombophilias. The prevalence of thrombophilia in these women was compared with its prevalence in the general population in our area. The prothrombin (OR 4.4; 95% CI 1.2‐16) and factor V Leiden (OR 4.5; 95% CI 2.1‐14.5) mutations were more common in our patients, compared with the general population, whereas women homozygous for the C677T mutation in the methylene tetrahydrofolate reductase gene (OR 0.45; 95% CI 0.13‐1.58) were not. It is recommended that women with a personal or strong family history of venous thromboembolism should be screened for the prothrombin mutation either before or early in pregnancy, in addition to screening for other thrombophilias. Screening for the MTHFR mutation does not appear to identify women at increased risk of maternal venous thrombosis.

Injecting drug use is a risk factor for deep vein thrombosis in women in Glasgow

Three hundred and twenty‐two consecutive women aged 16–70 years who presented with objectively confirmed symptomatic venous thromboembolism (VTE) were studied to determine precipitating factors for thrombosis. One hundred and eighty‐seven presented with deep vein thrombosis (DVT), 116 with either definite or possible pulmonary embolism (PE) and 19 with both DVT and PE. Injecting drug use (IDU) via femoral vein puncture was a common risk factor for DVT, associated with 21·4% of all cases of DVT and 52·4% of cases of DVT in women under 40 years. All women with drug‐related thrombosis presented with DVT. None presented with symptomatic PE. A number of clinically diagnosed DVT associated with IDU were also documented, suggesting that IDU may be the most common risk factor for DVT in our region. DVT associated with IDU presents significant management challenges.

Influence of demographic factors on antithrombin III activity in a healthy population

Summary. Antithrombin III (AT III) activity has been measured in 9669 healthy blood donors (5525 male and 4144 female). The distribution of AT III is approximately ‘normal’ with mean 105·6 iu/dl and standard deviation 11·2; however, definite age and sex related variations are evident. Pre‐menopausal females have lower mean AT III compared to their male contemporaries who have remarkably stable mean AT III until 45 years, after which there is a gradual decline. In contrast, post‐menopausal females have higher mean AT III than both males of the same age and younger pre‐menopausal females. Concurrent hormone replacement therapy inhibits this rise. The use of hormonal preparations is associated with a 4 iu/dl reduction of mean AT III in younger females but not in those over 30 years. Smoking may result in a mild increase in AT III of doubtful clinical significance. On‐going genetic and family studies are expected to predict a prevalence rate of congenital AT III deficiency in excess of the previously reported figure of 0·02%. The authors consider these observed variations as minor and recommend the use of a single reference range for AT III activity, but that particular care be taken when interpreting results in pill‐taking females and the elderly.

Guideline on aspects of cancer-related venous thrombosis

The guideline was drafted by a writing group identified by the Haemostasis and Thrombosis Task Force of the British Committee for Standards in Haematology (BCSH). All the authors are consultants in haematology in the UK. A search was performed of PubMed and Embase using the term ‘cancer’ combined with ‘thrombosis’, ‘treatment’, ‘prophylaxis’ and ‘clinical presentation’. The search covered articles published up until December 2014. Only human studies were included and articles not written in English were excluded. References in recent reviews were also examined. The writing group produced the draft guideline, which was subsequently revised by consensus by members of the Haemostasis and Thrombosis Task Force of the BCSH and the BCSH executive. The guideline was then reviewed by the sounding board of the British Society for Haematology (BSH). This comprises 50 or more members of the BSH who have reviewed the guidance and commented on the content and application to the UK setting. The ‘GRADE’ system was used to quote levels and grades of evidence, details of which can be found at: http://www.bcshguidelines.com/BCSH_PROCESS/EVIDENCE_LEVELS_AND_GRADES_OF_RECOMMENDATION/43_GRADE.html. The objective of this guideline is to provide healthcare professionals with clear guidance on the prevention and management of venous thromboembolism (VTE) in patients with cancer and to advise on an approach to screening for cancer in patients with unprovoked VTE in whom cancer was not initially suspected based on clinical grounds.

Unfavourable cardiovascular disease risk profiles in a cohort of Dutch and British haemophilia patients

Cardiovascular disease (CVD) mortality is reported to be decreased in haemophilia patients, but reports on the prevalence of CVD risk factors are conflicting. A cross-sectional assessment of CVD risk profiles was performed in a large cohort of haemophilia patients. Baseline data on CVD risk factors of 709 Dutch and UK haemophilia patients aged ≥30 years were analysed and compared with the general age-matched male population. CVD risk profiles were assessed using the QRISK®2-2011 and SCORE algorithms. Although QRISK® 2 was only validated in the UK, comparison with SCORE indicated similar properties of QRISK®2 in both Dutch and UK patients (correlation 0.86). Mean age was 49.8 years. Hypertension was more common in haemophilia patients than in the general population (49% vs. 40%), while the prevalences of obesity and hypercholesterolaemia were lower (15 vs. 20% and 44 vs. 68%, respectively), and those of diabetes and smoking were similar. The predicted 10-year QRISK®2 risk was significantly higher in haemophilia patients than in the general population (8.9 vs. 6.7%), indicating more unfavourable cardiovascular disease risk profiles. This increased risk became apparent after the age of 40 years. Our results indicate an increased prevalence of hypertension and overall more unfavourable CVD risk profiles in haemophilia patients compared with the general age-matched male population.

Increased prevalence of hypertension in haemophilia patients

An increased prevalence of hypertension is reported in haemophilia patients, but data from large, unbiased studies are lacking. The aim of our study was to cross-sectionally assess the prevalence of hypertension in a large cohort of 701 haemophilia patients. Blood pressure (BP) measurements performed in 386 Dutch and 315 UK haemophilia patients aged 30 years or older were analysed and compared with the general age-matched male population. Mean values of up to three BP measurements were used when available. Hypertension was defined as BP over 140/90 mmHg and/or the use of antihypertensive medication. A total of 49% of patients had severe haemophilia. Mean age was 49.8 years. The prevalence of hypertension was significantly higher in haemophilia patients (49%, 95% confidence interval [CI] 45-53) than in the general population (40%, 95% CI 37-43). The prevalence of hypertension was higher in patients with severe haemophilia than in those with non-severe disease, but similar across haemophilia types and in Dutch and UK patients. Multiple BP measurements were available for 70%.The prevalence of hypertension was similar in patients with multiple BP measurements and the complete cohort. Hypertension was not significantly associated with renal function, a history of renal bleeding or with infection with hepatitis C or HIV, but it was associated with overweight/obesity and age. In conclusion, the prevalence of hypertension is higher in haemophilia patients than in the general population. The cause of this increased prevalence is unknown. Blood pressure measurements should be part of standard care in haemophilia patients aged 30 years or older.