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.

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.

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.

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.

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.

Effective and safe use of recombinant factor VIIa (NovoSeven) in elderly mild haemophilia A patients with high-titre antibodies against factor VIII.

Three patients with mild haemophilia A who developed high-titre antibodies against factor VIII at high age are reported. These patients had only a limited number of exposure days of FVIII concentrates in the past. The patients had to undergo surgery or presented with recurrent bleeding episodes. Treatment with recombinant FVIIa (rFVIIa) was effective and safe. Despite the high age and the presence of coronary heart disease in one of the patients, no adverse events or thrombotic complications occurred. These cases illustrate that the physician should always be alert on the development of inhibitors, also in elderly patients with mild haemophilia, in whom FVIII inhibitors had never been detectable before and that treatment with rFVIIa was effective and well-tolerated.

Vitamin K status and bone mass in women with and without aortic atherosclerosis: a population-based study.

Gammacarboxyglutamate (Gla) is an uncommon amino acid formed by vitamin K action. Increasing evidence indicates that Gla-proteins are involved in the regulation of calcification processes in both bone tissue and atherosclerotic vessel wall. In a population-based study we have previously shown that in a group of 113 postmenopausal women the presence of abdominal aortic calcifications is associated with a reduced vitamin K status. In the present study we investigated whether this reduced vitamin K status was also associated with differences in bone mass or circulating calciotropic hormone levels. Serum immunoreactive osteocalcin with low affinity for hydroxyapatite (irOCfree) was used as a marker for vitamin K status. After correction for age it was found that women with atherosclerotic calcifications had a 7% lower bone mass as measured by metacarpal radiogrammetry (mean difference: 3.2 mm2, 95% CI: -0. 2-6.5, P = 0.06). No differences between both groups of women were observed for serum intact parathyroid hormone (PTH) and serum 25-hydroxyvitamin D levels. In the atherosclerotic women (n = 34), markers for vitamin K status were inversely associated with bone mass (r = -0.47, P = 0.013), whereas no such association was found in the nonatherosclerotic women (n = 79). It is concluded that the atherosclerotic women in this study may be at higher risk for osteoporotic fractures as evidenced by their lower bone mass and higher serum irOCfree levels. The finding that in atherosclerotic women vitamin K status is associated with bone mass supports our hypothesis that vitamin K status affects the mineralization processes in both bone and in atherosclerotic plaques.

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.

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.

Role of vitamin K in bone metabolism.

Vitamin K is a cofactor required for the formation of gamma-carboxyglutamate (Gla) residues in proteins. Osteoblasts produce at least three different Gla-containing proteins: osteocalcin, matrix Gla-protein, and protein S. After cellular secretion of these proteins, the main part of each remains bound to the hydroxyapatite matrix in bone, but their function remains unclear. Part of the newly synthesized osteocalcin is also set free into the bloodstream, where it may be used as a diagnostic marker for bone formation. Several studies have demonstrated that a poor vitamin K status is associated with an increased risk of osteoporotic bone fractures. Whether vitamin K supplementation will reduce the rate of bone loss in postmenopausal women remains a matter of debate.

A specific colorimetric staining method for gamma-carboxyglutamic acid-containing proteins in polyacrylamide gels.

In this paper we describe a specific staining method for gamma-carboxyglutamic acid (Gla)-containing proteins in polyacrylamide gels. The procedure is based on the colorimetric detection of Gla using 4-diazobenzenesulfonic acid and has the advantage of being simple and fast (1 h). The detection limit is 9.4 pmol for prothrombin and 150 pmol for osteocalcin. It is demonstrated that Gla-proteins can be visualized independent of the presence of an excess of contaminating non-Gla-proteins. The technique may be used for screening of large number of fractions during the purification of Gla-proteins from complex protein mixtures.

Vitamin K-induced changes in markers for osteoblast activity and urinary calcium loss.

The objective of this study was to identify subjects in whom vitamin K has an effect on markers for calcium and bone metabolism and to detect hitherto-unnoticed correlations between vitamin K-induced changes in these markers. Participants in our studies were apparently healthy women, in whom we measured serum-immunoreactive osteocalcin (irOC) before and after adsorption to hydroxylapatite; total serum alkaline phosphatase (T-AP) and bone-specific alkaline phosphatase (B-AP); and fasting urinary calcium and creatinine. We describe a trial among 145 women who were treated with vitamin K (1 mg/day) for 2 weeks, and a prospective placebo-controlled trial among two groups each of 70 postmenopausal women with a treatment period of 3 months. It turned out that in elderly women vitamin K induced increased levels of serum irOC with a high affinity for hydroxylapatite (irOCbound), whereas that with low affinity (irOCfree) remained unaffected. In placebo-treated women the ratio irOCfree/irOCbound shifted from 0.38 to 0.65 around the 50th year of age. This shift was not found in vitamin K-treated women. After 3 months of treatment the vitamin K-induced changes in irOCbound were correlated with changes in B-AP, whereas irOCfree was correlated to urinary calcium excretion. In fast losers of urinary calcium vitamin K induced a 30% decrease of calcium excretion. The hypothesis is put forward that irOCbound may be a marker for bone formation, that serum irOCfree may be a marker for bone resorption, and that the serum irOCfree/irOCbound ratio may become a marker for skeletal remodeling.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Effects of vitamin K and oral anticoagulants on urinary calcium excretion.

In a subgroup of postmenopausal women vitamin K induced a decrease of the urinary calcium loss. This effect was significant (P < 0.0001) in the so-called fast losers of calcium (calcium/creatinine ratio > 0.5). To find out whether vitamin K antagonists would have an opposite effect, a study was started among 141 persons on long-term oral anticoagulant therapy. In this population the number of fast losers was recorded, and compared to that in a group of age- and sex-matched non-treated controls. Notably in young men the fraction of fast losers was significantly higher in the anticoagulant-treated group than in the control group (25 v 0%, P < 0.02). Differences between treated and nontreated groups may also be found in other markers for calcium and bone metabolism, notably in serum osteocalcin concentration and in urinary hydroxyproline excretion. The conclusion of our study is that oral anticoagulant treatment must be regarded as a potential risk factor for a high loss of urinary calcium.