Factors associated with prescription of oral anticoagulation for atrial fibrillation in older people living in care homes in Wales: a routine data linkage study 2003–2018

Background

Prescription of oral anticoagulants (OAC) is paramount for stroke prevention in people with atrial fibrillation (AF), but treatment decisions in older care home residents are complicated by frailty, multi-morbidity and heightened stroke and bleeding risk. There is a paucity of data on factors influencing the decision to prescribe OAC in this high-risk population who are under-represented in research studies.

Purpose

To explore the factors associated with OAC prescription for care home residents aged ≥65 years with AF.

Methods

Nationwide retrospective cohort study of people aged ≥65 years entering a care home in Wales between 1 January 2003 and 31 December 2018, using anonymised individual-level electronic health record and administrative data sources available within the Secure Anonymised Information Linkage Databank. Unadjusted and adjusted logistic regression models were used to explore the association between resident characteristics and OAC prescription or non-prescription.

Results

Between 2003 and 2018, 14,493 people with AF aged ≥65 years became new residents in care homes in Wales and 7,057 (48.7%) were prescribed OAC (32.7% in 2003 compared to 72.7% in 2018), Figure 1. Increasing age and prescription of antiplatelet therapy were associated with lower odds of OAC prescription (adjusted odds ratio [aOR] 0.96 per one year age increase [95% confidence interval, 0.95 to 0.96] and aOR 0.91 [0.84 to 0.98], respectively). Conversely, prior venous thromboembolism (aOR 4.06 [3.17 to 5.20]), advancing frailty (mild: aOR 4.61 [3.95 to 5.38]; moderate: aOR 6.69 [5.74 to 7.80]; severe: aOR 8.42 [7.16 to 9.90]) and year of care home entry in the post-non-vitamin K antagonist oral anticoagulant (NOAC) era from 2011 onwards (aOR 1.91 [1.76 to 2.06]) were associated with higher odds of OAC prescription, Figure 2.

Conclusions

The proportion of care home residents prescribed OAC therapy has increased over time with the introduction of NOACs in 2011, but OAC prescription rates are still sub-optimal. Although there is an expected rise in OAC prescribing for increasingly frail people, further work is needed to investigate the interaction with deprivation and other socio-economic and demographic factors to assess potential inequalities in prescribing across these groups. Targeted educational tools for clinicians are needed to address barriers to OAC prescription for AF, such as older age and separate indications for antiplatelet therapy.

Funding Acknowledgement

Type of funding sources: None.

Prevalence and outcomes of atrial fibrillation in older people living in care homes in Wales: a routine data linkage study 2003–2018

Background

Older care home residents are a high-risk group of people with atrial fibrillation (AF) who are under-represented in clinical trials. Improved understanding of AF epidemiology and management in this population is paramount for health and social care organisations to strategically plan services.

Purpose

To determine the trends in AF prevalence and compare adverse health outcomes in older care home residents aged ≥65 years with AF compared to those without AF.

Methods

Retrospective cohort study of people entering a care home between 2003–2018 using nationwide, population-scale anonymised health and administrative data, provisioned from the Secure Anonymised Information Linkage (1 January 2000–31st December 2018). Direct standardisation was used to calculate AF prevalence by year of care entry (2010–2018). Cox regression analyses were used to estimate the risk of adverse health outcomes.

Results

Between 2003 and 2018, 86,602 people aged ≥65 years became new residents in care homes in Wales. Residents with AF (n=14,493) had a significantly higher risk (adjusted hazard ratio [aHR], 95% confidence interval [CI]) of cardiovascular (aHR 1.27 [1.17 to 1.37], p<0.001) and all-cause mortality (aHR 1.14 [1.11 to 1.17], p<0.001), Figure 1. The risk (sub-distribution hazard ratio [sHR], 95% CI) of ischaemic stroke (adjusted sHR 1.55 [1.36 to 1.76], p<0.001) and cardiovascular hospitalisation (adjusted sHR 1.28 [1.22 to 1.34], p<0.001) was also higher in residents with AF, even when mortality was considered a competing event, Figure 1. There was no significant change in age- and sex-standardised prevalence of AF between 2010 and 2018, 16.79% (95% CI 15.85 to 17.94) and 17.02% (95% CI 16.05 to 17.98), respectively (absolute change 2010–2018: 0.06% [95% CI: −1.38 to 1.50], p=0.93), Figure 2.

Conclusions

This study demonstrates unique data on the epidemiology of AF and associated outcomes in older care home residents. Whilst the prevalence of AF remained stable between 2010–2018, residents with AF had significantly higher risk of adverse health events. Treatment of AF in accordance with guidelines is critical in this population to optimise management and reduce adverse health outcomes.

Funding Acknowledgement

Type of funding sources: None.

Measurement of Aspirin Concentrations in Portal and Systemic Blood in Pigs: Effect on Platelet Aggregation, Thromboxane and Prostacyclin Production

Low doses of enteric-coated aspirin were administered orally to pigs. Plasma aspirin concentrations measured in blood obtained simultaneously from permanent catheters in a systemic artery and portal vein for 6 hours after dosage showed a large variation in the plasma aspirin concentration : time profile between pigs. After 50 mg single dose the ratio of the arterial : portal area under the plasma concentration versus time curve (AUC) was 0.63 ± 0.08 (mean ± SE, n = 6). In three pigs which received all three dosage regimens, the arterial : portal AUC ratios were 0.48 ± 0.05 after 50 mg single dose, 0.52 ± 0.02 after 100 mg single dose and 0.47 ± 0.02 after 100 mg daily for 1 week. Platelet aggregation in response to sodium arachidonate (1.65 mM) was completely abolished after chronic aspirin administration of 100 mg daily. Thromboxane production (pg/ 106 platelets) induced by this stimulus decreased from 536 ± 117 before aspirin to 57 ± 14 after aspirin (mean ± SE, n = 4; p = 0.03). Aortic prostacyclin synthesis, measured as 6-keto PGF1α (ng/disc after 10 min incubation), was 1.66 ± 0.28 (mean ± SE, n = 4) in untreated pigs and 0.95 ± 0.25 (n = 5) in treated pigs (p = 0.07). Results from this study support the idea that a difference between aspirin concentrations in the portal and systemic circulations can be achieved. Whether this can be translated into a clinically useful differential effect on the vessel wall compared to the platelet remains to be determined.

Baseline and treatment-related changes in thrombin generation in patients with multiple myeloma

The prothrombotic risk in multiple myeloma (MM) could be potentially assessed by thrombin generation (TG) assays. TG was performed using Calibrated Automated Thrombography with 5 and 1 pM tissue factor. We compared baseline TG among 24 MM patients, 19 MGUS, and 50 healthy controls, and assessed change in TG in MM patients during the initial treatment period at 1, 2, and 3 months. MM subjects demonstrated increased FVIII and VWF:Ag levels pretreatment, and a prothrombotic TG phenotype with increased velocity index, reduced lag time and time-to-peak, and increased resistance to thrombomodulin inhibition. There were no significant changes in TG with treatment for the majority of parameters, however, MM subjects exhibited persistent elevation of velocity index throughout treatment. Two subjects developed thrombosis during the study period despite thromboprophylaxis. This study provides information on the optimal conditions for examining TG as a predictor of thrombotic risk in MM patients.

Effects of an air pollution personal alert system on health service usage in a high-risk general population: a quasi-experimental study using linked data

BACKGROUND

There is no evidence to date on whether an intervention alerting people to high levels of pollution is effective in reducing health service utilisation. We evaluated alert accuracy and the effect of a targeted personal air pollution alert system, airAware, on emergency hospital admissions, emergency department attendances, general practitioner contacts and prescribed medications.

METHODS

Quasi-experimental study describing accuracy of alerts compared with pollution triggers; and comparing relative changes in healthcare utilisation in the intervention group to those who did not sign-up. Participants were people diagnosed with asthma, chronic obstructive pulmonary disease (COPD) or coronary heart disease, resident in an industrial area of south Wales and registered patients at 1 of 4 general practices. Longitudinal anonymised record linked data were modelled for participants and non-participants, adjusting for differences between groups.

RESULTS

During the 2-year intervention period alerts were correctly issued on 208 of 248 occasions; sensitivity was 83.9% (95% CI 78.8% to 87.9%) and specificity 99.5% (95% CI 99.3% to 99.6%). The intervention was associated with a 4-fold increase in admissions for respiratory conditions (incidence rate ratio (IRR) 3.97; 95% CI 1.59 to 9.93) and a near doubling of emergency department attendance (IRR=1.89; 95% CI 1.34 to 2.68).

CONCLUSIONS

The intervention was associated with increased emergency admissions for respiratory conditions. While findings may be context specific, evidence from this evaluation questions the benefits of implementing near real-time personal pollution alert systems for high-risk individuals.

Effects of an air pollution personal alert system on health service usage in a high-risk general population: a quasi-experimental study using linked data

BACKGROUND

There is no evidence to date on whether an intervention alerting people to high levels of pollution is effective in reducing health service utilisation. We evaluated alert accuracy and the effect of a targeted personal air pollution alert system, airAware, on emergency hospital admissions, emergency department attendances, general practitioner contacts and prescribed medications.

METHODS

Quasi-experimental study describing accuracy of alerts compared with pollution triggers; and comparing relative changes in healthcare utilisation in the intervention group to those who did not sign-up. Participants were people diagnosed with asthma, chronic obstructive pulmonary disease (COPD) or coronary heart disease, resident in an industrial area of south Wales and registered patients at 1 of 4 general practices. Longitudinal anonymised record linked data were modelled for participants and non-participants, adjusting for differences between groups.

RESULTS

During the 2-year intervention period alerts were correctly issued on 208 of 248 occasions; sensitivity was 83.9% (95% CI 78.8% to 87.9%) and specificity 99.5% (95% CI 99.3% to 99.6%). The intervention was associated with a 4-fold increase in admissions for respiratory conditions (incidence rate ratio (IRR) 3.97; 95% CI 1.59 to 9.93) and a near doubling of emergency department attendance (IRR=1.89; 95% CI 1.34 to 2.68).

CONCLUSIONS

The intervention was associated with increased emergency admissions for respiratory conditions. While findings may be context specific, evidence from this evaluation questions the benefits of implementing near real-time personal pollution alert systems for high-risk individuals.

Intra-operative parathyroid hormone monitoring in patients with parathyroid cancer

BACKGROUND

Intra-operative parathyroid hormone (PTH) monitoring (IPM) is 97% accurate in predicting postoperative eucalcemia in sporadic primary hyperparathyroidism (SPHPT). However, its usefulness in parathyroid cancer has not been demonstrated. This study reports IPM accuracy during surgical resections for parathyroid cancer.

METHODS

Eight of 556 consecutive patients with SPHPT underwent parathyroidectomy using IPM and had parathyroid cancer. Operative success was defined as eucalcemia > six months and operative failure/persistent cancer as hypercalcemia within six months of parathyroidectomy. The IPM criterion for operative success was defined as a >50% decrease of peripheral PTH levels from the highest either pre-incision or pre-excision values, 10 minutes after resection.

RESULTS

In eight patients, 11 operations were performed. Ten operations (91%) resulted in >50% intra-operative PTH decrease. However, in only seven (70%) of these resections, eucalcemia was achieved for >6 months with five of these seven (71%) procedures being initial en bloc resections. The remaining 3/10 (30%) operations with >50% intra-operative PTH decrease resulted in operative failures. In the last operation, intraoperative parathormone monitoring (IPM) correctly predicted operative failure. IPM sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy in predicting outcome were 100, 40, 70, 100, and 75%, respectively.

CONCLUSIONS

IPM with the criterion of >50% PTH drop from the highest level is less accurate in predicting operative success in parathyroid cancer when compared to SPHPT. A >50% intra-operative PTH level decrease in patients with parathyroid cancer, particularly in reoperative cases, is less predictive of complete resection. The initial recognition of this disease followed by proper resection remains essential in the treatment of parathyroid cancer.

In vitro kinetics of factor VIII activity in patients with mild haemophilia A and a discrepancy between one-stage and two-stage factor VIII assay results

In some mild haemophilia A patients (discrepant haemophilia), factor VIII coagulant activity (FVIII:C) levels, by one-stage assay are more than double than those by two-stage assay. This may be due to the longer incubation times (10-12 min) in the two-stage assay. This study aimed to determine the time course of the activation phase of the two-stage assay, using both classical coagulation and chromogenic detection methods. In both systems, for equivalent patients (equivalent FVIII:C levels by one-stage and two-stage assays, n = 6, all different mutations), similar FVIII:C results were obtained with short- or long-incubation times. In contrast, plasma from discrepant patients (n = 8, five different mutations) showed higher FVIII:C at shorter incubation times than after longer incubation times. In the chromogenic assay, FVIII:C levels were higher after incubation for 2 min (23-56%, mean 41%) than after 10 min (19-41%, mean 29%). In the classical coagulation assay, FVIII:C levels were higher at shorter incubation times (21-64%, mean 37%) than with the longer incubation times usually used (13-29%, mean 23%). These time-course experiments have verified that the longer incubation time used in the two-stage assay is at least partly responsible for the lower FVIII:C measured by that assay in discrepant haemophilia.

Low detection rate of antibodies to non-functional epitopes on factor VIII in patients with hemophilia A and negative for inhibitors by Bethesda assay

In patients with hemophilia A who have an inhibitor to factor (F)VIII measured by Bethesda assay, enzyme-linked immunosorbent assay (ELISA) can also be used to detect the inhibitor. In some studies non-inhibitory antibodies were also detected by ELISA in many patients who were negative by Bethesda assay. Our aim was to investigate whether there is a higher detection rate of FVIII antibodies by ELISA compared with Bethesda assay. We also compared outcomes using three different preparations of recombinant FVIII (rFVIII) to coat the microtiter plates for ELISA. Inhibitor detection by ELISA generally agreed with the Bethesda method. Only four of 26 patients with no clinical suspicion of an inhibitor and with no detectable inhibitor by Bethesda assay showed a non-inhibitory antibody by ELISA, and three of these were only weakly positive. Patients with severe hemophilia A and the intron 22 inversion (n = 21) did not show a higher incidence of non-inhibitory antibodies compared with those without that mutation. Finally, we found that the formulation of rFVIII has a small effect on ELISA performance, mainly in detection of low-level antibody. The results of the present study are in contrast to and fail to confirm previously published reports showing a higher incidence of non-inhibitory antibodies in hemophilia A.

Identification of von Willebrand disease type 2N (Normandy) in Australia: a cross-laboratory investigation using different methods

We report on a cross-laboratory study of type 2N von Willebrand disease (vWD). We tested 101 selected plasma samples for factor VIII and factor VIII binding activity of von Willebrand factor (vWF). Of these plasma samples, 31 were cotested by 2 specialist centers using different detection procedures for vWF-factor VIII binding: there was good agreement between results obtained by chromogenic assay and enzyme-linked immunosorbent assay. In total, 8 patients with type 2N vWD were identified. The 2-stage factor VIII assay detected a deficiency of factor VIII relative to vWF antigen in all 8 patients; the 1-stage factor VIII assay detected a relative deficiency in only 3 patients. Four patients were homozygous for the most common type 2N mutation (R854Q), 3 patients were presumed to be compound heterozygotes, and in 1 patient no type 2N mutations were identified. In this study of patients from 5 specialist centers in Australia, type 2N vWD was found in 5 families. The 2-stage factor VIII assay was more useful as a screening test than the 1-stage assay, and both vWF-factor VIII binding assays were equally effective.

Tainted love: content analysis of documents written by accused spousal abusers to their victims

This study analyzed themes in documents written by 22 male accused spousal abusers to their female victims. Using Pence's Power and Equity model (1998), 86% of the themes denied equity and expressed power and control in the relation. Of these, 28% minimized or denied the abuse, 24% used the children to manipulate the victim, 16% showed disrespect for the victim, and 14% invoked male privilege (including God's ordination of the abusive relation). These hallmarks of tainted love are rooted in the desire of the accused abuser to maintain power and control over the victim.

Classification of the kinetics of factor VIII inhibitors in haemophilia A: plasma dilution studies are more discriminatory than time-course studies

Factor VIII inhibitors have previously been classified as type I or type II using complex experiments that study the time course of inactivation of factor VIII and the effect of varying the antibody concentration. Classification may be important to better understand inhibitor behaviour in vivo. To determine the most reliable method of classifying the kinetics of factor VIII inactivation, we studied 11 patients with haemophilia A, comprising five severe, three mild and three acquired cases, and compared the classification obtained from plasma dilution studies and time-course studies. The plasma dilution studies showed two distinctly different patterns: a steep slope with complete FVIII:C inactivation at high antibody concentrations for type I inhibitors and a FVIII:C plateau with incomplete inactivation for type II inhibitors. Six type I (four severe, one mild and one acquired) and two type II (one mild and one acquired) inhibitors were classified using either plasma samples or purified and concentrated IgG, while the remaining were undetermined owing to insufficient available plasma. In contrast, the time-course studies could not discriminate between these groups. We recommend that plasma dilution studies be used for the classification of in vitro kinetics of factor VIII inhibitors.

Reovirus sigmaNS protein is required for nucleation of viral assembly complexes and formation of viral inclusions

Progeny virions of mammalian reoviruses are assembled in the cytoplasm of infected cells at discrete sites termed viral inclusions. Studies of temperature-sensitive (ts) mutant viruses indicate that nonstructural protein sigmaNS and core protein mu2 are required for synthesis of double-stranded (ds) RNA, a process that occurs at sites of viral assembly. We used confocal immunofluorescence microscopy and ts mutant reoviruses to define the roles of sigmaNS and mu2 in viral inclusion formation. In cells infected with wild-type (wt) reovirus, sigmaNS and mu2 colocalize to large, perinuclear structures that correspond to viral inclusions. In cells infected at a nonpermissive temperature with sigmaNS-mutant virus tsE320, sigmaNS is distributed diffusely in the cytoplasm and mu2 is contained in small, punctate foci that do not resemble viral inclusions. In cells infected at a nonpermissive temperature with mu2-mutant virus tsH11.2, mu2 is distributed diffusely in the cytoplasm and the nucleus. However, sigmaNS localizes to discrete structures in the cytoplasm that contain other viral proteins and are morphologically indistinguishable from viral inclusions seen in cells infected with wt reovirus. Examination of cells infected with wt reovirus over a time course demonstrates that sigmaNS precedes mu2 in localization to viral inclusions. These findings suggest that viral RNA-protein complexes containing sigmaNS nucleate sites of viral replication to which other viral proteins, including mu2, are recruited to commence dsRNA synthesis.

The extent of nursing research utilization in general medical and surgical wards

There has been extensive speculation about the lack of research utilization in nursing but little attempt to quantify this phenomenon outside of North America. The current demands for evidence-based practice necessitate research utilization as one element of the process. As part of a larger project, this study aimed to describe the extent of research utilization by registered nurses in general medical and surgical wards in the Scottish Health Service. A postal survey was conducted for nurses to self-report their level of utilization of 14 research-based practices. The 14 practices represented examples of direct, indirect and methodological utilization of research. A research utilization score was constructed for each of the 14 practices and a total mean score constructed for all 14 practices. A random two-stage stratified sampling resulted in a total sample of 936 nurses from 25 hospitals. A 73% response rate was achieved. The total mean research utilization score for all nurses across all 14 nursing practices suggests that on average, nurses had heard, believed in and were beginning to use the practices. The sampling technique over-represents nurses in large hospitals and charge nurses, hence a weighting calculation on all scores was completed. There was little difference in weighted and unweighted scores. Scores on individual practices ranged from 60% (405/680) of nurses never having heard of a practice to 85% (574/680) always using a practice. This approach provides a valid and reliable method of assessing the extent of nursing research utilization. In several of the practices, nurses are making significant attempts at research-based practice. The level of research utilization compares favourably with research completed in North America and provides a baseline for United Kingdom and other country studies.

A study of the utilization of research in practice and the influence of education

This paper reports part of a multi-phase study which aimed to investigate the extent to which nurses utilize research and to identify factors associated with research utilization. The findings presented examine the influence of education upon research utilization. Firstly, a survey of registered nurses working in general medical and surgical wards in Scotland was conducted. 680/936 (72.6%) nurses returned self-report questionnaires to measure the level of utilization of 14 research based practices and assess the presence of potential influencing factors. This was then followed up through interviews with a sub-sample of nurses. An association was found between a higher educational level and research utilization. The nurses reported that in courses as opposed to study days, they were expected to engage in study and read and complete course work whereas attendance at study days could be an entirely passive experience and was often more of a morale booster. Nurses who read at least one journal regularly, had had more study leave, or had attended research courses also had a higher level of research utilization.

Reovirus-induced apoptosis requires activation of transcription factor NF-kappaB

Reovirus infection induces apoptosis in cultured cells and in vivo. To identify host cell factors that mediate this response, we investigated whether reovirus infection alters the activation state of the transcription factor nuclear factor kappa B (NF-kappaB). As determined in electrophoretic mobility shift assays, reovirus infection of HeLa cells leads to nuclear translocation of NF-kappaB complexes containing Rel family members p50 and p65. Reovirus-induced activation of NF-kappaB DNA-binding activity correlated with the onset of NF-kappaB-directed transcription in reporter gene assays. Three independent lines of evidence indicate that this functional form of NF-kappaB is required for reovirus-induced apoptosis. First, treatment of reovirus-infected HeLa cells with a proteasome inhibitor prevents NF-kappaB activation following infection and substantially diminishes reovirus-induced apoptosis. Second, transient expression of a dominant-negative form of IkappaB that constitutively represses NF-kappaB activation significantly reduces levels of apoptosis triggered by reovirus infection. Third, mutant cell lines deficient for either the p50 or p65 subunits of NF-kappaB are resistant to reovirus-induced apoptosis compared with cells expressing an intact NF-kappaB signaling pathway. These findings indicate that NF-kappaB plays a significant role in the mechanism by which reovirus induces apoptosis in susceptible host cells.

Grandpaternal mosaicism in a family with isolated haemophilia A

About one third of cases of haemophilia A have no family history of the disorder, and 20% are thought to be due to a new mutation. In the family reported here, a 3 bp deletion was detected in DNA from the proband at the 3' end of exon 15. Direct sequencing of genomic DNA prepared from blood and buccal cells of the grandfather revealed both normal and mutant sequences, suggesting that he is a mosaic for this mutation. This highlights the usefulness of mutation detection, both for accurate genetic counselling and to determine the origin of new mutations of haemophilia.

Reovirus growth in cell culture does not require the full complement of viral proteins: identification of a sigma1s-null mutant

The reovirus sigma1s protein is a 14-kDa nonstructural protein encoded by the S1 gene segment. The S1 gene has been linked to many properties of reovirus, including virulence and induction of apoptosis. Although the function of sigma1s is not known, the sigma1s open reading frame is conserved in all S1 gene sequences determined to date. In this study, we identified and characterized a variant of type 3 reovirus, T3C84-MA, which does not express sigma1s. To facilitate these experiments, we generated two monoclonal antibodies (MAbs) that bind different epitopes of the sigma1s protein. Using these MAbs in immunoblot and immunofluorescence assays, we found that L929 (L) cells infected with T3C84-MA do not contain sigma1s. To determine whether sigma1s is required for reovirus infection of cultured cells, we compared the growth of T3C84-MA and its parental strain, T3C84, in L cells and Madin-Darby canine kidney (MDCK) cells. After 48 h of growth, yields of T3C84-MA were equivalent to yields of T3C84 in L cells and were fivefold lower than yields of T3C84 in MDCK cells. After 7 days of growth following adsorption at a low multiplicity of infection, yields of T3C84-MA and T3C84 did not differ significantly in either L cells or MDCK cells. To determine whether sigma1s is required for apoptosis induced by reovirus infection, T3C84-MA and T3C84 were tested for their capacity to induce apoptosis, using an acridine orange staining assay. In these experiments, the percentages of apoptotic cells following infection with T3C84-MA and T3C84 were equivalent. These findings indicate that nonstructural protein sigma1s is not required for reovirus growth in cell culture and does not influence the capacity of reovirus to induce apoptosis. Therefore, reovirus replication does not require the full complement of virally encoded proteins.

ADP, adrenaline and serotonin stimulate inositol 1,4,5-trisphosphate production in human platelets

Although adenosine diphosphate (ADP) is a well-known stimulus of platelet aggregation, it is not the generally accepted view that ADP stimulates phosphatidylinositolbisphosphate (PtdIns(4,5)P2) hydrolysis. Using a very sensitive competitive receptor binding assay for inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), we have detected Ins(1,4,5)P3 production at early ( < 10 s) time points after stimulation of human platelets by the weak agonists ADP, adrenaline and serotonin (5-hydroxytryptamine, 5-HT). When adrenaline or 5-HT was combined with ADP in the presence of aspirin, there was a significant potentiation of ADP-induced platelet aggregation, but there was no potentiation of Ins(1,4,5)P3 generation. Also, the increases in intracellular calcium (Ca2+) concentrations stimulated by ADP were not potentiated by adrenaline in the presence of aspirin. Therefore, the synergism between the purinergic and adrenergic pathways of platelet activation occurs downstream from PtdIns(4,5)P2 hydrolysis and intracellular Ca2+ mobilization, although prior to platelet aggregation.

Reovirus-induced apoptosis of MDCK cells is not linked to viral yield and is blocked by Bcl-2

In this study, we investigated the relationship between reovirus-induced apoptosis and viral growth. Madin-Darby canine kidney (MDCK) epithelial cells infected with prototype reovirus strains type 1 Lang (T1L) or type 3 Dearing (T3D) were found to undergo apoptosis, and T3D induced apoptosis of MDCK cells to a substantially greater extent than T1L. By using T1L x T3D reassortant viruses, we found that differences in the capacities of these strains to induce apoptosis are determined by the viral S1 and M2 gene segments. These genes encode viral outer-capsid proteins that play important roles in viral entry into cells. T1L grew significantly better in MDCK cells than T3D, and these differences in growth segregated with the viral L1 and M1 gene segments. The L1 and M1 genes encode viral core proteins involved in viral RNA synthesis. Bcl-2 overexpression in MDCK cells inhibited reovirus-induced apoptosis but did not substantially affect reovirus growth. These findings indicate that differences in the capacities of reovirus strains to induce apoptosis and grow in MDCK cells are determined by different viral genes and that premature cell death by apoptosis does not limit reovirus growth in MDCK cells.

Direct mutation analysis as the preferred method for carrier diagnosis in families with isolated cases of haemophilia B

Approximately one-third of haemophilia B cases are described as isolated due to their occurrence in families with no prior history of the disorder. In this report, two families with isolated haemophilia B were studied by the standard method of restriction fragment length polymorphism (RFLP) analysis coupled with factor IX activity and antigen levels with the aim of achieving carrier diagnoses. The limitations of using this approach in the determination of carrier status were highlighted by diagnostic problems arising in both families. The problems included difficulty in interpreting bioassay results, homozygosity for the RFLP marker in a key family member and the possibility of germline mosaicism. Unequivocal carrier diagnosis in the two families was ultimately achieved by direct mutation analysis.

Detection of carriers of haemophilia A: use of bioassays and restriction fragment length polymorphisms (RFLP)

BACKGROUND

Haemophilia A is a sex-linked bleeding disorder carried by unaffected females. Currently, the two main methods used for the determination of carrier status in women from families with haemophilia A are bioassays and DNA-based assays using restriction fragment length polymorphisms (RFLP).

AIM

The aim of this paper was to assess the current usefulness of these two methods.

METHODS

Bioassays measured factor VIII coagulation activity by a two-stage coagulation assay and von Willebrand antigen by immunoelectrophoresis. RFLP were determined with two intragenic probes (p114 and p486) and two linked probes (St14 and DX13). Data were analysed using a Bayesian analysis to allow for all possible recombination events. We also incorporated an estimate for the risk of mosaicism into calculations in isolated haemophilia families. Both bioassays and RFLP were used to determine carrier status in 63 women, 31 from known haemophilia families and 32 from families of isolated cases. The techniques were assessed for their ability to classify the patients as normal (p < 0.2) or carrier (p > 0.7). Where applicable, intron 22 inversion was also tested.

RESULTS

In the known families, six women could not be classified after bioassay, but all could be classified by RFLP. Of the 32 women from families of isolated cases, eight were unclassified by bioassay and 12 were not definitely classified using RFLP. However, RFLP was useful in determining that a recent mutation had occurred in six of the eight families in which DNA from the grandparents was available.

CONCLUSION

For diagnosis of carriers of haemophilia, RFLP is the preferred method in familial haemophilia, but is less useful in isolated haemophilia.

Differences in the capacity of reovirus strains to induce apoptosis are determined by the viral attachment protein sigma 1

Reoviruses are important models for studies of viral pathogenesis; however, the mechanisms by which these viruses produce cytopathic effects in infected cells have not been defined. In this report, we show that murine L929 (L) cells infected with prototype reovirus strains type 1 Lang (TIL) and type 3 Dearing (T3D) undergo apoptosis and that T3D induces apoptosis to a substantially greater extent than T1L. Using T1L x T3D reassortant viruses, we found that differences in the capacity of T1L and T3D to induce apoptosis are determined by the viral S1 gene segment, which encodes the viral attachment protein sigma 1 and the non-virion-associated protein sigma 1s. Apoptosis was induced by UV-inactivated, replication-incompetent reovirus virions, which do not contain sigma 1s and do not mediate its synthesis in infected cells. Additionally, T3D-induced apoptosis was inhibited by anti-reovirus monoclonal antibodies that inhibit T3D cell attachment and disassembly. These results indicate that sigma 1, rather than sigma 1s, is required for induction of apoptosis by the reovirus and suggest that interaction of virions with cell surface receptors is an essential step in this mechanism of cell killing.

Platelet activation induced by a murine monoclonal antibody directed against a novel tetra-span antigen

MAb 14A2.H1 identifies a novel low-abundance platelet surface antigen, PETA-3, which is a member of the tetra-span (TM4) family. This MAb brings about platelet aggregation and mediator release, which is completely inhibitable by prostaglandin E1, and partially inhibitable by aspirin and ketanserin. Platelet activation by MAb 14A2.H1 is dependent on interaction with both the platelet Fc receptor, Fc gamma RII, and the specific antigen as it was prevented by either a blocking MAb to Fc gamma RII (IV.3) or F(ab')2 fragments of 14A2.H1. The extent of platelet activation by the antibody varied considerably between donors, and is believed to reflect the polymorphism of Fc gamma RII. Subaggregating concentrations of 14A2.H1 synergized with other platelet agonists, ADP, adrenaline, collagen and serotonin, indicating signalling via a pathway distinct from these activators. Synergy was also blocked by MAb IV.3, or F(ab')2 fragments of 14A2.H1. The similar low copy number of PETA-3 and Fc gamma RII in the platelet membrane (approximately 1000/platelet), together with the dependence on Fc gamma RII for activation by MAb 14A2.H1, suggests that PETA-3 may be a component of the Fc gamma RII signal transducing complex in platelets.

Anticoagulation and the GP patient

The use of anticoagulant drugs requires a knowledge of the essential elements of their pharmacology and mechanisms of action. This article illustrates the marked differences for the drugs warfarin, heparin and aspirin.

Sequence diversity within the reovirus S2 gene: reovirus genes reassort in nature, and their termini are predicted to form a panhandle motif

To better understand genetic diversity within mammalian reoviruses, we determined S2 nucleotide and deduced sigma 2 amino acid sequences of nine reovirus strains and compared these sequences with those of prototype strains of the three reovirus serotypes. The S2 gene and sigma 2 protein are highly conserved among the four type 1, one type 2, and seven type 3 strains studied. Phylogenetic analyses based on S2 nucleotide sequences of the 12 reovirus strains indicate that diversity within the S2 gene is independent of viral serotype. Additionally, we found marked topological differences between phylogenetic trees generated from S1 and S2 gene nucleotide sequences of the seven type 3 strains. These results demonstrate that reovirus S1 and S2 genes have distinct evolutionary histories, thus providing phylogenetic evidence for lateral transfer of reovirus genes in nature. When variability among the 12 sigma 2-encoding S2 nucleotide sequences was analyzed at synonymous positions, we found that approximately 60 nucleotides at the 5' terminus and 30 nucleotides at the 3' terminus were markedly conserved in comparison with other sigma 2-encoding regions of S2. Predictions of RNA secondary structures indicate that the more conserved S2 sequences participate in the formation of an extended region of duplex RNA interrupted by a pair of stem-loops. Among the 12 deduced sigma 2 amino acid sequences examined, substitutions were observed at only 11% of amino acid positions. This finding suggests that constraints on the structure or function of sigma 2, perhaps in part because of its location in the virion core, have limited sequence diversity within this protein.

Potentiation of ADP-induced aggregation in human platelet-rich plasma by 5-hydroxytryptamine and adrenaline

1. We have used dose-response curves to quantitate the potentiation of adenosine 5'-diphosphate (ADP)-induced aggregation and thromboxane (TXA2) generation by 5-hydroxytryptamine (5-HT) and adrenaline in human citrated platelet-rich plasma. We have also quantitated the inhibition of these responses by aspirin, ketanserin and yohimbine, singly and in pairs. 2. Ketanserin (5 microM) inhibited TXA2 production and the second wave of platelet aggregation induced by a range of concentrations of ADP alone. This indicates that endogenous 5-HT, released from the platelet dense granules, contributes significantly to responses induced by ADP. 3. When 5-HT (10 microM) was added before ADP, a lower concentration of ADP was required to cause 50% aggregation and TXA2 generation. The ratio of ADP concentrations (CR) to cause 50% aggregation in the presence and absence of 5-HT was 2.1 when only added 5-HT was considered, and 5.0 when endogenous 5-HT was also taken into account. 4. Potentiation of ADP-induced aggregation by 5-HT also occurred in the presence of aspirin, resulting in a CR of 2.3. As expected, ketanserin inhibited potentiation by 5-HT in the presence and absence of aspirin. Although aspirin caused substantial inhibition of aggregation induced by ADP and 5-HT (CR 3.4), further inhibition occurred when ketanserin was also present (CR 6.5). 5. A subthreshold concentration of adrenaline (0.25 microM) caused substantial potentiation of ADP-induced aggregation in the absence (CR 4.0) and presence (CR 2.0) of aspirin. As expected, yohimbine (9 microM) inhibited this potentiation.Maximum TXA2 generation induced by ADP increased from 32.5 to 59.4 pg per 106 platelets when adrenaline was present. Aggregation induced by ADP and adrenaline was markedly inhibited by aspirin (CR 5.1) but was further inhibited when yohimbine (9 microM) was also present (CR 10.0).6. Results from this in vitro study show ketanserin and yohimbine have the potential to be used in combination with aspirin as antithrombotic agents in vivo.

The antiplatelet effect of daily low dose enteric-coated aspirin in man: a time course of onset and recovery

We have studied the onset and recovery of inhibition of platelet function by low dose aspirin. Enteric-coated aspirin 50mg daily was administered to five human volunteers for five weeks and then 100mg daily was given for a further five weeks. We studied platelet aggregation and thromboxane formation in response to a range of stimuli: ADP, adrenaline, arachidonate and collagen, and also measured thromboxane formation after coagulation of whole blood (serum thromboxane). The onset of inhibition of platelet aggregation was progressive over several days for each of the four platelet stimuli, and was synchronous with the inhibition of thromboxane formation. Maximum inhibition occurred by day three for the weak stimuli ADP and adrenaline, by day five for the stronger stimuli arachidonate and collagen, but did not occur until day eight for serum thromboxane. Further inhibitory effects on both aggregation and thromboxane generation were observed after 100mg daily. Two weeks after the cessation of aspirin the responses to collagen and arachidonate and serum thromboxane had returned to normal. Platelet aggregation in response to the weaker stimuli, ADP and adrenaline, still showed detectable inhibition two weeks after cessation of aspirin, but had returned to normal by four weeks. These experiments provided no evidence for an effect of aspirin on platelets separate to its effect on cyclooxygenase. The onset and recovery of inhibition of platelet function by low dose aspirin was dependent on the strength of the stimulus studied.

Measurement of aspirin concentrations in portal and systemic blood in pigs: effect on platelet aggregation, thromboxane and prostacyclin production

Low doses of enteric-coated aspirin were administered orally to pigs. Plasma aspirin concentrations measured in blood obtained simultaneously from permanent catheters in a systemic artery and portal vein for 6 hours after dosage showed a large variation in the plasma aspirin concentration: time profile between pigs. After 50 mg single dose the ratio of the arterial: portal area under the plasma concentration versus time curve (AUC) was 0.63 +/- 0.08 (mean +/- SE, n = 6). In three pigs which received all three dosage regimens, the arterial: portal AUC ratios were 0.48 +/- 0.05 after 50 mg single dose, 0.52 +/- 0.02 after 100 mg single dose and 0.47 +/- 0.02 after 100 mg daily for 1 week. Platelet aggregation in response to sodium arachidonate (1.65 mM) was completely abolished after chronic aspirin administration of 100 mg daily. Thromboxane production (pg/10(6) platelets) induced by this stimulus decreased from 536 +/- 117 before aspirin to 57 +/- 14 after aspirin (mean +/- SE, n = 4; p = 0.03). Aortic prostacyclin synthesis, measured as 6-keto PGF1 alpha (ng/disc after 10 min incubation), was 1.66 +/- 0.28 (mean +/- SE, n = 4) in untreated pigs and 0.95 +/- 0.25 (n = 5) in treated pigs (p = 0.07). Results from this study support the idea that a difference between aspirin concentrations in the portal and systemic circulations can be achieved. Whether this can be translated into a clinically useful differential effect on the vessel wall compared to the platelet remains to be determined.

Inhibition of platelet aggregation and thromboxane production by low concentrations of aspirin in vitro

1. The aspirin concentrations previously reported to inhibit platelet aggregation in vitro (40-500 mumol/l) are much greater than those required in vivo in man (5 mumol/l). 2. Human platelet-rich plasma was incubated with buffer or various aspirin concentrations at 37 degrees C for up to 4.5 h. Platelet aggregation and thromboxane generation were measured in response to collagen (0.4-6.3 micrograms/ml) and adenosine 5'-pyrophosphate (0.5-4 mumol/l). 3. The concentration of aspirin needed to inhibit platelet aggregation in response to a critical concentration of aggregating agent (lowest concentration to cause greater than 50% aggregation) was lower than that required for higher concentrations of aggregating agent. 4. With more prolonged incubation times with aspirin, lower concentrations of aspirin inhibited platelet aggregation. 5. Inhibition of platelet aggregation and thromboxane formation by 10 mumol/l aspirin was maximal by 90 min. There was progressive inhibition by 3 mumol/l aspirin during incubation for 270 min. By the end of this time there was also significant inhibition by 1 mumol/l aspirin. 6. The apparent discrepancy between inhibitory aspirin concentrations in vivo and those observed in vitro in previous studies appears to have been resolved by extending the incubation time of platelets with low aspirin concentrations, thus mimicking the conditions in vivo.

A dose-ranging study of the antiplatelet effect of enteric coated aspirin in man

Enteric coated aspirin was given to eight human volunteers in escalating doses (20, 40, 60, 80, 100 mg daily), each dose being given over two weeks. In addition, to measure the maximum effect of aspirin, each volunteer was given two single doses of 600 mg of soluble aspirin. At the end of each dosing interval we measured platelet aggregation and thromboxane formation in response to four aggregating agents and to whole blood coagulation. The doses of aspirin required to inhibit platelet aggregation in response to various stimuli were: for collagen 60-80 mg, for adenosine diphosphate and adrenaline 60 mg, and for arachidonate 40 mg. For maximum inhibition of thromboxane formation the doses were: for collagen greater than 100 mg, for adenosine diphosphate and adrenaline 60 mg, for arachidonate 80 mg, and for whole blood coagulation 100 mg. Different aspirin doses are required to inhibit the responses to different stimuli. Furthermore, for some stimuli, inhibition of thromboxane generation may require more aspirin than is required for inhibition of aggregation. The clinical implications of these findings are uncertain since we do not know which stimuli are important in arterial thrombosis in man.

Platelet function in platelet concentrates and in whole blood

Platelet function was studied in CPD whole blood stored at 4 degrees C for one and three days and in platelet concentrates stored at room temperature for the same periods of time. Comparisons were made of platelet shape, nucleotide content, beta-thromboglobulin (beta TG) liberated during storage, and platelet aggregation in response to ADP, collagen, sodium arachidonate and ristocetin. It was found that in whole blood the shape of the platelets was less discoid than in platelet concentrates. However, platelet aggregation in response to ADP, collagen, and sodium arachidonate was preserved better in whole blood than in platelet concentrates. Platelet nucleotides were the same in whole blood as in platelet concentrates, but the plasma levels of beta TG were less in whole blood. The results show that as judged by aggregation, beta TG release and nucleotide content, platelets from whole blood were at least as functional as those from platelet concentrates. However, platelets from whole blood had lost their discoid shape, which suggests that they would have a short survival in the circulation.

Destruction of ristocetin cofactor by coagulation at 4 degrees C

Ristocetin cofactor (VIIIR:RCo) and factor VIII-related antigen (VIIIR:Ag) were measured in anticoagulated and non-anticoagulated blood incubated at 4 degrees C, room temperature (RT) or 37 degrees C for 24 hours. A marked decrease in VIIIR:RCo, to almost undetectable levels, and a smaller decrease in VIIIR:Ag occurred when whole blood clotted at 4 degrees C. These changes were slight or absent when blood clotted at RT or 37 degrees C. VIIIR:RCo lost at 4 degrees C was not recoverable by further incubation at 37 degrees C but the less-marked loss of VIIIR:Ag was partially recovered. In blood which had clotted at 4 degrees C there was a change in the electrophoretic profile of VIIIR:Ag on crossed immunoelectrophoresis: there was more anodal migration of the VIIIR:Ag peak, consistent with a decrease in the mean molecular size. Further experiments showed that the decrease in VIIIR:RCo during coagulation at 4 degrees C preceded the decrease in fibrinogen levels. In cell-free plasma VIIIR:RCo also decreased markedly when coagulation occurred at 4 degrees C. The results show that loss of VIIIR:RCo occurs when blood is allowed to clot at 4 degrees C: this is not due to cryoprecipitation and does not require the presence of blood cells. The data suggest that it is probably caused by plasma proteases activated early in the coagulation pathway.

Haematological characteristics of the common marmoset (Callithrix jacchus jacchus)

Blood cell indices and parameters of haemostasis were studied in the common marmoset. The majority of the results were similar to those found in man. Differences from man were that the prothrombin time was shorter in the marmoset, higher concentrations of aggregating stimuli were required to cause platelet aggregation, and marmoset platelets did not aggregate under the influence of adrenalin. There was sexual dimorphism evident in the data for fibrinogen concentration and for platelet count, both of which were higher in females than in males. Marmoset platelets were very similar in ultrastructure to those of man.