Estimating the hazard rate difference from case-cohort studies.

The case-cohort design, among many two-phase sampling designs, substantially reduces the cost of an epidemiological study by selecting more informative participants within the full cohort for expensive variable measurements. Despite their benefits, additive hazards models, which estimate hazard differences, have rarely been used for the analysis of case-cohort studies due to the lack of software and application examples. In this paper, we describe a newly developed estimation method that fits the additive hazards models to general two-phase sampling studies along with the R package addhazard that implements it. It allows for missing covariates among cases, cohort stratification, robust variances, and the incorporation of auxiliary information from the full cohort to enhance inference precision. We demonstrate the use of this tool to estimate the association of the risk of coronary heart disease (CHD) with biomarkers high-sensitivity C-reactive protein (hs-CRP) and Lipoprotein-associated phospholipase A2 (Lp-PLA2) by analyzing the Atherosclerosis Risk in Communities Study, which adopted a two-phase sampling design for studying these two biomarkers. We show that the use of auxiliary variables from the full cohort based on calibration techniques improves the precision of the hazard difference being estimated. We observe a synergistic effect of the two biomarkers among participants with lower LDL cholesterol (LDL-C): the CHD hazard rate attributable to the combined action of high hs-CRP and high Lp-PLA2 exceeded the sum of the CHD hazard rate attributable to each one independently by 11.58 (95% CI 2.16-21.01) cases per 1000 person-years. With higher LDL-C, we observe the CHD hazard rate attributable to the combined action of high hs-CRP and medium Lp-PLA2 was less than the sum of their individual effects by 13.42 (95% CI 2.44-24.40) cases per 1000 person-years. This demonstration serves the dual purposes of illustrating analysis techniques and providing insights about the utility of hs-CRP and Lp-PLA2 for identifying the high-risk population of CHD that the traditional risk factors such as the LDL-C may miss. Epidemiologists are encouraged to use this new tool to analyze other case-cohort studies and incorporate auxiliary variables embedded in the full cohort in their analysis.

Concentrated citrate locking in order to reduce the long-term complications of central venous catheters: a randomized controlled trial in patients with hematological malignancies.

PURPOSE AND METHODS: Central venous catheter (CVC)-related thrombosis and infections are frequently occurring complications in patients with hematological malignancies. At present, heparin is most often used as a locking solution. Trisodium citrate (TSC) had been shown to be a very effective antimicrobial catheter locking in hemodialysis patients. We performed a prospective randomized phase III multicenter trial to determine the efficacy of TSC as a locking solution compared to heparin in preventing CVC-related thrombosis and infections in patients with hematological malignancies. RESULTS: Thirty-four episodes of CVC-related bloodstream infections (CVC-BSI) occurred in the 108 patients who were randomized to locking with heparin compared with 35 episodes in the 99 patients who were randomized to locking with TSC (P = 0.654). We did find seven times more CVC-BSI with gram-negative rods in CVCs locked with heparin (P = 0.041). The cumulative incidence of symptomatic thrombosis was 10% in the heparin group and 5% in the TSC group (hazard ratio 0.525; 95% confidence interval 0.182-1.512). CONCLUSION: This study shows that locking with TSC in patients with hematological malignancies significantly reduced the incidence of CVC-BSI with gram-negative rods. However, the incidence of CVC-BSI with coagulase-negative staphylococcus or CVC-related thrombosis was not reduced by TSC locking.

Patients' representations of their end-stage renal disease: relation with mortality.

BACKGROUND: Self-regulation theory explains how patients' illness perceptions influence self-management behaviour (e.g. via adherence to treatment). Following these assumptions, we explored whether illness perceptions of ESRD-patients are related to mortality rates. METHODS: Illness perceptions of 182 patients participating in the NECOSAD-2 study in the period between December 2004 and June 2005 were assessed. Cox proportional hazard models were used to estimate whether subsequent all-cause mortality could be attributed to illness perception dimensions. RESULTS: One-third of the participants had died at the end of the follow-up. Mortality rates were higher among patients who believed that their treatment was less effective in controlling their disease (perceived treatment control; RR = 0.71, P = 0.028). This effect remained stable after adjusting for sociodemographic and clinical variables (RR = 0.65, P = 0.015). CONCLUSIONS: If we consider risk factors for mortality, we tend to rely on clinical parameters rather than on patients' representations of their illness. Nevertheless, results from the current exploration may suggest that addressing patients' personal beliefs regarding the effectiveness of treatment can provide a powerful tool for predicting and perhaps even enhancing survival.

Thrombotic and infectious complications of central venous catheters in patients with hematological malignancies.

Central venous catheters (CVCs) have considerably improved the management of patients with hematological malignancies, by facilitating chemotherapy, supportive therapy and blood sampling. Complications of insertion of CVCs include mechanical (arterial puncture, pneumothorax), thrombotic and infectious complications. CVC-related thrombosis and infections are frequently occurring complications and may cause significant morbidity in patients with hematological malignancies. CVC-related thrombosis and infections are related and can therefore not be seen as separate entities. The incidence of symptomatic CVC-related thrombosis had been reported to vary between 1.2 and 13.0% of patients with hematological malignancy. The incidence of CVC-related bloodstream infections varies between 0.0 and 20.8%. There is need for a specific approach regarding diagnosis and treatment of CVC-related thrombosis and infection with specific attention to the preservation of the catheter. Since data on CVC-related infections and thrombosis in hematological patients have been obtained mainly from retrospective studies of small sample size, prospective, randomized studies of prophylactic measures concerning CVC-related thrombosis and infection are warranted.

Low protein Z levels but not the protein Z gene G79A polymorphism are a risk factor for ischemic stroke.

BACKGROUND: Protein Z (PZ) is a vitamin K-dependent plasma protein that plays a role in both pro-and anticoagulant pathways, but its exact physiological function remains unclear. The aim of this study was to determine the association between the G79A PZ gene polymorphism in intron F, PZ levels and the occurrence of ischemic stroke. METHODS: We performed a case-control study in 118 Caucasian patients with first ever ischemic stroke or TIA confirmed by CT, and 113 age-and sex-matched population controls. Venous blood samples for PZ levels were collected 7 to 14 days and 3 months after stroke onset. Estimates of relative risk (odds ratios) were adjusted for vascular risk factors. RESULTS: The adjusted relative risk of ischemic stroke associated with PZ levels in the lowest quartile versus the highest quartile was 3.0 (95% CI: 1.1-8.7) at 7-14 days, and 5.1 (95% CI: 1.2-21.9) at 3 months after the stroke. PZ levels in the convalescent sample were significantly lower than in the acute sample. In the convalescent sample, odds ratios increased with lower quartiles of protein Z level (test for trend p=0.02). Thirty-nine patients (33%) and 32 (28%) controls were heterozygous for the G79A PZ gene polymorphism and 4 (3%) patients and 4 (4%) controls had the AA-genotype. The PZ levels were significantly lower in subjects with the AA-genotype and intermediate in heterozygote subjects. The odds ratio of ischemic stroke associated with A-allele carriers versus GG-homozygotes was 1.2 (95% CI: 0.7-2.1). CONCLUSION: No association between the G79A PZ gene polymorphism and the occurrence of stroke was observed. However, low PZ levels are independently associated with an increased risk of ischemic stroke.

Procalcitonin-guided antibiotic therapy in patients with fever in a general emergency department population: a multicentre non-inferiority randomized clinical trial (HiTEMP study).

OBJECTIVES: Overuse of broad-spectrum antibiotics in emergency departments (EDs) results in antibiotic resistance. We determined whether procalcitonin (PCT) -guided therapy can be used to reduce antibiotic regimens in EDs by investigating efficacy, safety and accuracy. METHODS: This was a non-inferiority multicentre randomized clinical trial, performed in two Dutch hospitals. Adult patients with fever ≥38.2°C (100.8°F) in triage were randomized between standard diagnostic workup (control group) and PCT-guided therapy, defined as standard workup with the addition of one single PCT measurement. The treatment algorithm encouraged withholding antibiotic regimens with PCT <0.5 µg/L, and starting antibiotic regimens at PCT ≥0.5 µg/L. Exclusion criteria were immunocompromised conditions, pregnancy, moribund patients, patients <72 h after surgery or requiring primary surgical intervention. Primary outcomes were efficacy, defined as number of prescribed antibiotic regimens; safety, defined as combined safety end point consisting of 30 days mortality, intensive-care unit admission, ED return visit within 2 weeks; accuracy, defined as sensitivity, specificity and area-under-the-curve (AUC) of PCT for bacterial infections. Non-inferiority margin for safety outcome was 7.5%. RESULTS: Between August 2014 and January 2017, 551 individuals were included. In the PCT-guided group (n = 275) 200 (73%) patients were prescribed antibiotic regimens, in the control group (n = 276) 212 (77%) patients were prescribed antibiotics (p 0.28). There was no significant difference in combined safety end point between the PCT-guided group, 29 (11%), and control group, 46 (16%) (p 0.16), with a non-inferiority margin of 0.46% (n = 526). AUC for confirmed bacterial infections for PCT was 0.681 (95% CI 0.633-0.730), and for CRP was 0.619 (95% CI 0.569-0.669). CONCLUSIONS: PCT-guided therapy was non-inferior in terms of safety, but did not reduce prescription of antibiotic regimens in an ED population with fever. In this heterogeneous population, the accuracy of PCT in diagnosing bacterial infections was poor. TRIAL REGISTRATION IN NETHERLANDS TRIAL REGISTER: http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=4949.

[A man with a primary diffuse B-cell lymphoma of the bone]. / Een man met aanhoudende pijn in zijn knie.

A 63-year-old man suffered from persistent pain in the left knee that did not respond to local injections with bupivacaine and triamcinolone acetonide. The first X-ray of the knee did not show any abnormalities, but eight months later a lytic lesion in the left tibia was seen on X-ray. A PET/CT scan and histopathologic analysis of a biopsy revealed a primary diffuse B-cell lymphoma of the bone.

[Erythema after subcutaneous heparin treatment]. / Erytheem na subcutane heparinetoediening.

BACKGROUND: Heparin-induced skin lesions are common. The majority are delayed-type hypersensitivity reactions to heparin or other components of the injection fluid. Differentiation from heparin-induced thrombocytopenia (HIT) skin lesions is important. The Warkentin 4T's score is helpful for assessment of the risk of HIT. CASE DESCRIPTION: A 36-year old female was treated with injections of tinzaparin for a deep vein thrombosis. After 16 days, she developed progressive thrombocytopenia and a skin lesion at one of the injection sites. She was diagnosed with "skin lesion consistent with HIT and caused by the use of low-molecular-weight heparin". The platelet count returned to normal and the severity of the skin lesion improved after replacement of tinzaparin with fondaparinux. CONCLUSION: In patients with skin lesions suspected of being caused by the use of heparin, a complete blood count needs to be made as quickly as possible. With a 4T's score ≥ 4, it is recommended that a skin biopsy and a laboratory HIT-test are performed. Heparin should be replaced by alternative anticoagulants by way of precaution.

Dendrimers in oral drug delivery application: current explorations, toxicity issues and strategies for improvement.

Dendrimers are emerging as potential novel nano-scaled material in drug delivery applications. An interesting area of application is oral drug delivery. In oral drug delivery, many drugs suffer from low bioavailability due to the presence of various biological barriers. Dendrimers have been shown to modulate tight junctions and the integrity of cellular membranes. This effect gives hope for dendrimer to be applied in oral drug delivery. Based on such properties, dendrimers are further surface-modified so that the system will be more suitable for oral delivery applications. Cationic dendrimers are commonly conjugated with neutral or negatively charged ligands, such as polyethylene glycol (PEG), to reduce potential toxicity in gastrointestinal (G.I.) tract. Dendrimers are also surfacemodified to inhibit the efflux effect of P-glycoprotein, which is one of the major drug efflux pumps in G.I. tract. Another interesting strategy is to directly conjugate or mix dendrimer with drugs either to form a dendrimer-drug conjugation or complex to deliver the drug. In this review, application of dendrimers in oral drug delivery will be discussed. The main focus is on the various surface modification strategies to design a more desirable dendrimer-based delivery system that fits the need in oral drug delivery.

Vitamin K intake and osteocalcin levels in women with and without aortic atherosclerosis: a population-based study.

Protein-bound gamma-carboxyglutamate (Gla) has been demonstrated in calcified atherosclerotic plaques. Vitamin K is required for the formation of Gla-residues. As the biological activity of Gla-proteins appears to be strictly dependent on the presence of the Gla-residues, vitamin K status may be an important factor in the development and progression of atherosclerotic calcifications. We studied the association of vitamin K status, as assessed by nutritional vitamin K intake and the measurements of two circulating immunoreactive osteocalcin (irOC) fractions, with aortic atherosclerosis in a population-based study of 113 postmenopausal women. Women with calcified lesions (n = 34) had a 42.9 micrograms lower mean age-adjusted dietary vitamin K intake/day (95% C.I. -6.6 to 92.5) than those without calcifications (n = 79). Atherosclerotic women had higher irOC levels with a low affinity for hydroxyapatite (irOCfree): age-adjusted difference of 0.32 ng/ml (95% C.I. 0.03 to 0.61). In addition, the high affinity irOC levels expressed as a percentage (hydroxyapatite binding capacity, HBC) were 5.12% (95% C.I. 1.32 to 8.92) lower in women with calcifications. Our study indicates that women with aortic atherosclerosis have an impaired vitamin K status as reflected by a lower nutritional vitamin K intake, an increased irOCfree level and a reduced HBC level. An impaired vitamin K status in subjects with atherosclerosis is compatible with the view that vitamin K or Gla-containing proteins are involved in the development of calcification of the vessel wall.

Serum osteocalcin as a marker for vitamin K-status in pregnant women and their newborn babies.

Osteocalcin (bone Gla-protein) is a vitamin K-dependent protein synthesized by osteoblasts. Its hydroxylapatite binding capacity (HBC) is generally used to estimate the Gla-content of circulating osteocalcin. Here we have used the HBC of serum osteocalcin as a marker for the vitamin K-status in pregnant women and their offspring. For all cases investigated the HBC values in the cord samples were substantially lower than in the corresponding maternal ones. Babies from mothers who had been treated with vitamin K during the last 6 weeks prior to delivery, had significantly higher HBC values than those from a placebo group. The results presented in this paper are indicative for a generally occurring vitamin K deficiency in newborns. At delivery the HBC in untreated women was low as well. In both the placebo- and the vitamin K-group a good correlation was found between the HBC values in paired samples from mother and child. Whether the maternal HBC value may be used as a prenatal marker for estimating the fetal vitamin K-status remains to be seen.

The relative effects of phylloquinone and menaquinone-4 on the blood coagulation factor synthesis in vitamin K-deficient rats.

Rats were made vitamin K-deficient by feeding them a 1:1 (w/w) mixture of a commercial vitamin K-depleted diet and boiled white rice. After one week of treatment the rats had developed severe vitamin K deficiency, resulting in Thrombotest values of 5-10% of the initial values. In this experimental system the efficacy of phylloquinone (K1) was compared with that of menaquinone-4 (MK-4) by measuring the extent to which the Thrombotest was normalized after the administration of varying doses of the respective vitamins. Oral administration of the vitamins showed that the efficacy of K1 was at least two-fold higher than that of MK-4. As comparable results were obtained after subcutaneous administration of the vitamins, we conclude that after oral administration the intestinal absorption had been quick and nearly complete. A less pronounced effect of K1 and MK-4 was found after colorectal administration. For both forms of vitamin K relatively high amounts (well above the physiological concentration) were required before significant effects on the Thrombotest could be observed. Therefore these data demonstrate the importance of sufficient dietary vitamin K consumption in rats. The efficacy of other menaquinones may be investigated in the same experimental animal model system.

Differences between exogenous and endogenous noradrenaline in the effects on vascular post-synaptic alpha 1- and alpha 2-adrenoceptors in man.

Effects of exogenous and endogenous noradrenaline, released by tyramine and lower body negative pressure (LBNP), on vascular post-synaptic alpha 1- and alpha 2-adrenoceptors have been compared in healthy volunteers. Intra-arterial (i.a.) infusions of noradrenaline and tyramine into the forearm were given in the presence of saline, of yohimbine and of doxazosin, and changes in forearm blood flow (FBF) were measured. Lower body negative pressure of -40 mmHg was applied without and with a continuous i.a. infusion of yohimbine and of doxazosin, and changes in FBF in both forearms were compared. Forearm blood flow was measured by venous occlusion plethysmography. Noradrenaline and tyramine reduced FBF dose-dependently and to the same extent. Both these vasoconstrictions were significantly reduced by yohimbine (P < 0.001 for both) as well as by doxazosin (P < 0.05 for noradrenaline and P < 0.001 for tyramine). The tyramine-induced vasoconstriction was more effectively reduced by doxazosin, whereas yohimbine reduced the noradrenaline-induced vasoconstriction more effectively. Lower body negative pressure reduced FBF in both forearms to the same extent. Doxazosin effectively inhibited the LBNP induced decrease in FBF (P < 0.05) whereas yohimbine had no effect (P > 0.05). These results are in accordance with a predominant intrasynaptic location of post-synaptic alpha 1-adrenoceptors and a predominant extrasynaptic location of post-synaptic alpha 2-adrenoceptors in human blood vessels.

Alpha 1- and alpha 2-adrenoceptor mediated vasoconstriction in the forearm: differences between normotensive and hypertensive subjects.

Alpha 1- and alpha 2-adrenoceptor mediated vasoconstriction were compared between 13 patients with essential hypertension and 13 normotensive controls, matched for age and sex. For this purpose changes in forearm blood flow induced by infusion of the selective alpha 1-adrenoceptor agonist methoxamine, the selective alpha 2-adrenoceptor agonist B-HT 933, the catecholamines adrenaline and noradrenaline and the alpha 2-adrenoceptor antagonist yohimbine were measured in both study groups. The catecholamines were infused together with propranolol to avoid beta-adrenergic effects. Forearm blood flow was measured by plethysmography. All agonists produced a dose-dependent vasoconstriction which was more pronounced in the hypertensive subjects but no preference was found for either the alpha 1- or alpha 2-adrenoceptor mediated vasoconstriction. Yohimbine induced a greater vasodilatation in the normotensive subjects. The greater vasoconstriction in the hypertensive patients could be explained by structural vascular changes. No evidence was found for an important role of alpha 2-adrenoceptor mediated vasoconstriction in essential hypertension.

Effects of exogenous adrenaline and noradrenaline on vascular postsynaptic alpha 1- and alpha 2-adrenoceptors in man.

The effects of adrenaline and noradrenaline on vascular postsynaptic alpha 1- and alpha 2-adrenoceptors were investigated in six healthy volunteers. The catecholamines were infused intra-arterially, in three cumulative doses, together with a continuous infusion of saline, doxazosin (alpha 1-selective antagonist), yohimbine (alpha 2-selective antagonist) or the combination of the two antagonists, and changes in forearm blood flow were measured by plethysmography. beta-adrenoceptor mediated effects of the catecholamines were prevented by concomitant intra-arterial infusion of propranolol. Adrenaline and noradrenaline reduced forearm blood flow dose-dependently and to the same extent. The vasoconstrictive effect of adrenaline and of noradrenaline was significantly reduced by doxazosin and by yohimbine, and, to a greater extent, by the combination of doxazosin and yohimbine. The magnitude of these reductions were approximately the same for adrenaline and noradrenaline. No changes in heart rate or blood pressure were observed during the infusions. It is concluded that exogenous adrenaline and noradrenaline produce vasoconstriction in the vasculature of the human forearm by stimulation of both postsynaptic alpha 1- and alpha 2-adrenoceptors.

Alpha-adrenergic receptors in human blood vessels.

The evidence for the presence of postjunctional alpha 1- and alpha 2-adrenoceptor subtypes in human blood vessels is reviewed. Experiments in healthy subjects are described that show that alpha 1- as well as alpha 2-adrenoceptor mediated vasoconstriction contribute to vascular smooth muscle tone and that adrenaline and noradrenaline have similar affinities for each subtype. In addition, evidence is presented for a preferential intrajunctional location of alpha 1-adrenoceptors and a preferential extrajunctional location of alpha 2-adrenoceptors in human blood vessels. It is concluded that at present postjunctional alpha-adrenoceptors in human blood vessels can be classified as alpha 1 and alpha 2. Despite the fact that both subtypes mediate vasoconstriction, these receptors are likely to subserve different physiological functions.

Effect of food composition on vitamin K absorption in human volunteers.

The human vitamin K requirement is not known precisely, but the minimal requirement is often assumed to be between 0.5 and 1 x 10(-6) g/kg body weight. In the present study we addressed the question to what extent circulating vitamin K concentrations are influenced by the form in which the vitamer is consumed. The experimental group consisted of five healthy volunteers who received phylloquinone after an overnight fast. On the first day of three successive weeks the participants consumed 1 mg (2.2 mumol) phylloquinone, either in the form of a pharmaceutical preparation (Konakion), or in the form of spinach + butter, or as spinach without added fat. Circulating phylloquinone levels after spinach with and without butter were substantially lower (7.5- and 24.3-fold respectively) than those after taking the pharmaceutical concentrate. Moreover, the absorption of phylloquinone from the vegetables was 1.5 times slower than from Konakion. In a second experiment in the same five volunteers it was shown that relatively high amounts of menaquinone-4 enter the circulation after the consumption of butter enriched with this vitamer. It is concluded that the bioavailability of membrane-bound phylloquinone is extremely poor and may depend on other food components, notably fat. The bioavailability of dietary vitamin K (phylloquinone + menaquinones) is lower than generally assumed, and depends on the form in which the vitamin is ingested. These new insights may lead to a revision of the recommended daily intake for vitamin K.