Power Analysis for the Likelihood-Ratio Test in Latent Markov Models: Shortcutting the Bootstrap p-Value-Based Method.

The latent Markov (LM) model is a popular method for identifying distinct unobserved states and transitions between these states over time in longitudinally observed responses. The bootstrap likelihood-ratio (BLR) test yields the most rigorous test for determining the number of latent states, yet little is known about power analysis for this test. Power could be computed as the proportion of the bootstrap p values (PBP) for which the null hypothesis is rejected. This requires performing the full bootstrap procedure for a large number of samples generated from the model under the alternative hypothesis, which is computationally infeasible in most situations. This article presents a computationally feasible shortcut method for power computation for the BLR test. The shortcut method involves the following simple steps: (1) obtaining the parameters of the model under the null hypothesis, (2) constructing the empirical distributions of the likelihood ratio under the null and alternative hypotheses via Monte Carlo simulations, and (3) using these empirical distributions to compute the power. We evaluate the performance of the shortcut method by comparing it to the PBP method and, moreover, show how the shortcut method can be used for sample-size determination.

Development of a new hazard scoring system in primary neuronal cell cultures for drug-induced acute neuronal toxicity identification in early drug discovery.

We investigated drug-induced acute neuronal electrophysiological changes using Micro-Electrode arrays (MEA) to rat primary neuronal cell cultures. Data based on 6-key MEA parameters were analyzed for plate-to-plate vehicle variability, effects of positive and negative controls, as well as data from over 100 reference drugs, mostly known to have pharmacological phenotypic and clinical outcomes. A Least Absolute Shrinkage and Selection Operator (LASSO) regression, coupled with expert evaluation helped to identify the 6-key parameters from many other MEA parameters to evaluate the drug-induced acute neuronal changes. Calculating the statistical tolerance intervals for negative-positive control effects on those 4-key parameters helped us to develop a new weighted hazard scoring system on drug-induced potential central nervous system (CNS) adverse effects (AEs). The weighted total score, integrating the effects of a drug candidate on the identified six-pivotal parameters, simply determines if the testing compound/concentration induces potential CNS AEs. Hereto, it uses four different categories of hazard scores: non-neuroactive, neuroactive, hazard, or high hazard categories. This new scoring system was successfully applied to differentiate the new compounds with or without CNS AEs, and the results were correlated with the outcome of in vivo studies in mice for one internal program. Furthermore, the Random Forest classification method was used to obtain the probability that the effect of a compound is either inhibitory or excitatory. In conclusion, this new neuronal scoring system on the cell assay is actively applied in the early de-risking of drug development and reduces the use of animals and associated costs.

High-Throughput Screening Assay for Detecting Drug-Induced Changes in Synchronized Neuronal Oscillations and Potential Seizure Risk Based on Ca2+ Fluorescence Measurements in Human Induced Pluripotent Stem Cell (hiPSC)-Derived Neuronal 2D and 3D Cultures.

Drug-induced seizure liability is a significant safety issue and the basis for attrition in drug development. Occurrence in late development results in increased costs, human risk, and delayed market availability of novel therapeutics. Therefore, there is an urgent need for biologically relevant, in vitro high-throughput screening assays (HTS) to predict potential risks for drug-induced seizure early in drug discovery. We investigated drug-induced changes in neural Ca2+ oscillations, using fluorescent dyes as a potential indicator of seizure risk, in hiPSC-derived neurons co-cultured with human primary astrocytes in both 2D and 3D forms. The dynamics of synchronized neuronal calcium oscillations were measured with an FDSS kinetics reader. Drug responses in synchronized Ca2+ oscillations were recorded in both 2D and 3D hiPSC-derived neuron/primary astrocyte co-cultures using positive controls (4-aminopyridine and kainic acid) and negative control (acetaminophen). Subsequently, blinded tests were carried out for 25 drugs with known clinical seizure incidence. Positive predictive value (accuracy) based on significant changes in the peak number of Ca2+ oscillations among 25 reference drugs was 91% in 2D vs. 45% in 3D hiPSC-neuron/primary astrocyte co-cultures. These data suggest that drugs that alter neuronal activity and may have potential risk for seizures can be identified with high accuracy using an HTS approach using the measurements of Ca2+ oscillations in hiPSC-derived neurons co-cultured with primary astrocytes in 2D.

Pregnancy rate after vasectomy reversal in a contemporary series: influence of smoking, semen quality and post-surgical use of assisted reproductive techniques.

UNLABELLED: Study Type - Outcomes (cohort series). Level of Evidence 2b What's known on the subject? and What does the study add? Microsurgical vasectomy reversal is an effective and cost-effective method of reinstating fertility in a man who has previously had a vasectomy. The current literature indicates that the success rate (i.e. potency and pregnancy rates) are dependent primarily on the time elapsed since vasectomy and the age of the female partner. Using a multivariate Cox regression model, evaluation of the influence of preoperative data (including smoking) and semen parameters indicates a significant influence of post-surgical sperm motility only, on time to first pregnancy. The use of assisted reproductive techniques, when natural pregnancy failed, was successful in ≈50% of couples who attempted this procedure and accounted for an absolute increase in pregnancy rate of 14%. OBJECTIVE: • To determine the influence of smoking, postoperative semen characteristics and the use of an assisted reproductive technique (ART) on pregnancy rate in a contemporary series of men undergoing vasectomy reversal. PATIENTS AND METHODS: • Between January 2002 and January 2009, 186 vasectomy reversals were performed. Of the 171 patients who could be contacted for follow-up, 162 attempted pregnancy and constitute the study group. • Semen analysis was performed 3 months after the procedure and at subsequent 3-monthly intervals. • Patient characteristics and surgical information were obtained from a computerized database, and follow-up data were collected by telephone interview. • A multivariate Cox regression model was used to discern possible prognosticators with respect to pregnancy outcome. RESULTS: • The overall patency rate was 91.4%, with a natural pregnancy rate of 44.4% and a subsequent 14.2% of patients conceiving using a ARTs resulting in a total pregnancy rate of 58.6%. Multiple pregnancies were obtained by 20.4% of couples. • Smoking of the male or female partner did not influence the probability of conception. • In a multivariate model that included, among other factors, time since vasectomy, female age and semen characteristics, only sperm motility was significantly related to natural pregnancy outcome. • The probability of obtaining a natural pregnancy within 2 years after surgery is 53% for men with sperm motility >20% (WHO a+b) compared to 19% for men with sperm motility <5% (P= 0.003). CONCLUSIONS: • A clear and significant association between sperm motility and the probability of conception was found, whereas smoking, female age and time since vasectomy appeared to have no influence on pregnancy outcome in this patient cohort. • The use of ARTs accounted for an absolute increase in pregnancy rate of 14.2%.

Identifying Acute Cardiac Hazard in Early Drug Discovery Using a Calcium Transient High-Throughput Assay in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

Introduction: Early identification of cardiac risk is essential for reducing late-stage attrition in drug development. We adapted the previously published cardiac hazard risk-scoring system using a calcium transient assay in human stem cell-derived CMs for the identification of cardiac risks recorded from the new hiPSC-CM line and investigated its predictivity and translational value based on the screening of a large number of reference and proprietary compounds. Methods: Evaluation of 55 reference drugs provided the translation of various pharmacological effects into a single hazard label (no, low, high, or very high hazard) using a Ca2+-sensitive fluorescent dye assay recorded by -by FDSS/µCell Functional Drug Screening System (Hamamatsu on hiPSC-CM line (FCDI iCell Cardiomyocytes2). Results: Application of the adapted hazard scoring system in the Ca2+ transient assay, using a second hiPS-CM line, provided comparable scoring results and predictivity of hazard, to the previously published scoring approach, with different pharmacological drug classes, as well as screening new chemical entities (NCE's) using a single hazard label from four different scoring levels (no, low, high, or very high hazard). The scoring system results also showed minimal variability across three different lots of hiPSC-CMs, indicating good reproducibility of the cell line. The predictivity values (sensitivity and specificity) for drug-induced acute cardiac risk for QT-interval prolongation and Torsade de pointes (TdPs) were >95% and statistical modeling confirmed the prediction of proarrhythmic risk. The outcomes of the NCEs also showed consistency with findings in other well-established in vitro and in vivo cardiac risk assays. Conclusion: Evaluation of a large list of reference compounds and internal NCEs has confirmed the applicability of the adaptations made to the previously published novel scoring system for the hiPSC-CMs. The validation also established the predictivity for drug-induced cardiac risks with good translation to other established preclinical in vitro and in vivo assays, confirming the application of this novel scoring system in different stem cell-CM lines for early cardiac hazard identification.

Direct nose to brain delivery of small molecules: critical analysis of data from a standardized in vivo screening model in rats.

The blood-brain barrier (BBB) is often a limiting factor for getting drugs in the brain. Bypassing the BBB by intranasal (IN), or also called nose to brain (NTB), route is an interesting and frequently investigated concept for brain drug delivery. However, despite the body of evidence for IN drug delivery in literature over the last decades, reproducibility and interpretation of animal data remain challenging. The objective of this project was to assess the feasibility and value of a standardized IN screening model in rats for the evaluation of direct brain delivery. A chemically diverse set of commercial and internal small molecules were tested in the in vivo model with different doses and/or formulations. Data were analyzed using different ways of ratio calculations: blood concentration at time of sacrifice, total exposure in blood (area under the curve, AUC) and the brain or olfactory bulb concentrations. The IN route was compared to another parenteral route to decide if there is potential direct brain transport. The results show that blood and tissue concentrations and ratios are highly variable and not always reproducible. Potential direct brain delivery was concluded for some compounds, however, sometimes depending on the analysis: using blood levels at sacrifice or AUC could lead to different conclusions. We conclude that a screening model for the evaluation of direct brain transport of small molecules is very difficult to achieve and a conclusion based on a limited number of animals with this variability is questionable.

Testing of acetaminophen in support of the international multilaboratory in vivo rat Pig-a assay validation trial.

Acetaminophen, a nonmutagenic compound as previously concluded from bacteria, in vitro mammalian cell, and in vivo transgenic rat assays, presented a good profile as a nonmutagenic reference compound for use in the international multilaboratory Pig-a assay validation. Acetaminophen was administered at 250, 500, 1,000, and 2,000 mg·kg-1 ·day-1 to male Sprague Dawley rats once daily in 3 studies (3 days, 2 weeks, and 1 month with a 1-month recovery group). The 3-Day and 1-Month Studies included assessments of the micronucleus endpoint in peripheral blood erythrocytes and the comet endpoint in liver cells and peripheral blood cells in addition to the Pig-a assay; appropriate positive controls were included for each assay. Within these studies, potential toxicity of acetaminophen was evaluated and confirmed by inclusion of liver damage biomarkers and histopathology. Blood was sampled pre-treatment and at multiple time points up to Day 57. Pig-a mutant frequencies were determined in total red blood cells (RBCs) and reticulocytes (RETs) as CD59-negative RBC and CD59-negative RET frequencies, respectively. No increases in DNA damage as indicated through Pig-a, micronucleus, or comet endpoints were seen in treated rats. All positive controls responded as appropriate. Data from this series of studies demonstrate that acetaminophen is not mutagenic in the rat Pig-a model. These data are consistent with multiple studies in other nonclinical models, which have shown that acetaminophen is not mutagenic. At 1,000 mg·kg-1 ·day-1 , Cmax values of acetaminophen on Day 28 were 153,600 ng/ml and 131,500 ng/ml after single and repeat dosing, respectively, which were multiples over that of clinical therapeutic exposures (2.6-6.1 fold for single doses of 4,000 mg and 1,000 mg, respectively, and 11.5 fold for multiple dose of 4,000 mg) (FDA 2002). Data generated were of high quality and valid for contribution to the international multilaboratory validation of the in vivo Rat Pig-a Mutation Assay.

Efficacy of subcutaneous doses and a new oral amorphous solid dispersion formulation of flubendazole on male jirds (Meriones unguiculatus) infected with the filarial nematode Brugia pahangi.

River blindness and lymphatic filariasis are two filarial diseases that globally affect millions of people mostly in impoverished countries. Current mass drug administration programs rely on drugs that primarily target the microfilariae, which are released from adult female worms. The female worms can live for several years, releasing millions of microfilariae throughout the course of infection. Thus, to stop transmission of infection and shorten the time to elimination of these diseases, a safe and effective drug that kills the adult stage is needed. The benzimidazole anthelmintic flubendazole (FBZ) is 100% efficacious as a macrofilaricide in experimental filarial rodent models but it must be administered subcutaneously (SC) due to its low oral bioavailability. Studies were undertaken to assess the efficacy of a new oral amorphous solid dispersion (ASD) formulation of FBZ on Brugia pahangi infected jirds (Meriones unguiculatus) and compare it to a single or multiple doses of FBZ given subcutaneously. Results showed that worm burden was not significantly decreased in animals given oral doses of ASD FBZ (0.2-15 mg/kg). Regardless, doses as low as 1.5 mg/kg caused extensive ultrastructural damage to developing embryos and microfilariae (mf). SC injections of FBZ in suspension (10 mg/kg) given for 5 days however, eliminated all worms in all animals, and a single SC injection reduced worm burden by 63% compared to the control group. In summary, oral doses of ASD formulated FBZ did not significantly reduce total worm burden but longer treatments, extended takedown times or a second dosing regimen, may decrease female fecundity and the number of mf shed by female worms.

Assessing Drug-Induced Long QT and Proarrhythmic Risk Using Human Stem-Cell-Derived Cardiomyocytes in a Ca2+ Imaging Assay: Evaluation of 28 CiPA Compounds at Three Test Sites.

The goal of this research consortium including Janssen, MSD, Ncardia, FNCR/LBR, and Health and Environmental Sciences Institute (HESI) was to evaluate the utility of an additional in vitro assay technology to detect potential drug-induced long QT and torsade de pointes (TdP) risk by monitoring cytosolic free Ca2+ transients in human stem-cell-derived cardiomyocytes (hSC-CMs). The potential proarrhythmic risks of the 28 comprehensive in vitro proarrhythmia assay (CiPA) drugs linked to low, intermediate, and high clinical TdP risk were evaluated in a blinded manner using Ca2+-sensitive fluorescent dye assay recorded from a kinetic plate reader system (Hamamatsu FDSS/µCell and FDSS7000) in 2D cultures of 2 commercially available hSC-CM lines (Cor.4U and CDI iCell Cardiomyocytes) at 3 different test sites. The Ca2+ transient assay, performed at the 3 sites using the 2 different hSC-CMs lines, correctly detected potential drug-induced QT prolongation among the 28 CiPA drugs and detected cellular arrhythmias-like/early afterdepolarization in 7 of 8 high TdP-risk drugs (87.5%), 6 of 11 intermediate TdP-risk drugs (54.5%), and 0 of 9 low/no TdP-risk drugs (0%). The results were comparable among the 3 sites and from 2 hSC-CM cell lines. The Ca2+ transient assay can serve as a user-friendly and higher throughput alternative to complement the microelectrode array and voltage-sensing optical action potential recording assays used in the HESI-CiPA study for in vitro assessment of drug-induced long QT and TdP risk.

Macrofilaricidal efficacy of single and repeated oral and subcutaneous doses of flubendazole in Litomosoides sigmodontis infected jirds.

Flubendazole (FBZ) is highly efficacious against filarial nematodes after parenteral administration and presents a promising macrofilaricidal drug candidate for the elimination of onchocerciasis and other filariae. In the present study the efficacy of a newly developed bioavailable amorphous solid dispersion (ASD) oral formulation of FBZ was investigated in the Litomosoides sigmodontis jird model. FBZ was administered to chronically infected, microfilariae-positive jirds by single (40mg/kg), repeated (2, 6 or 15mg/kg for 5 or 10 days) oral (OR) doses or single subcutaneous (SC) injections (2 or 10mg/kg). Jirds treated with 5 SC injections at 10mg/kg served as positive controls, with untreated animals used as negative controls. After OR doses, FBZ is rapidly absorbed and cleared and the exposures increased dose proportionally. SC administered FBZ was slowly released from the injection site and plasma levels remained constant up to necropsy eight weeks after treatment end. Increasing single SC doses caused less than dose-proportional exposures. At necropsy, all animals receiving 1x or 5x 10mg/kg SC FBZ had cleared all adult worms and the 1x 2mg/kg SC treatment had reduced the adult worm burden by 98%. 10x 15mg/kg OR FBZ reduced the adult worm burden by 95%, whereas 1x 40mg/kg and 5x 15mg/kg OR reduced the worm burden by 85 and 84%, respectively. Microfilaremia was completely cleared at necropsy in all animals of the SC treatment regimens, while all oral FBZ treatment regimens reduced the microfilaremia by >90% in a dose and duration dependent manner. In accordance, embryograms from female worms revealed a FBZ dose and duration dependent inhibition of embryogenesis. Histological analysis of the remaining female adult worms showed that FBZ had damaged the body wall, intestine and most prominently the uterus and uterine content. Results of this study demonstrate that single and repeated SC injections and repeated oral administrations of FBZ have an excellent macrofilaricidal effect.

Short-course, oral flubendazole does not mediate significant efficacy against Onchocerca adult male worms or Brugia microfilariae in murine infection models.

The Onchocerca ochengi adult implant and Brugia malayi microfilariemic Severe-Combined Immunodeficient (SCID) mouse models are validated screens to measure macrofilaricidal and microfilaricidal activities of candidate onchocerciasis drugs. The purpose of this study was to assess whether 5 daily sub-cutaneous (s.c.) injections of standard flubendazole (FBZ) suspension (10mg/kg), a single s.c. injection (10mg/kg) or 5 daily repeated oral doses of FBZ amorphous solid dispersion (ASD) formulation (0.2, 1.5 or 15mg/kg) mediated macrofilaricidal efficacy against O. ochengi male worms implanted into SCID mice. The direct microfilaricidal activity against circulating B. malayi microfilariae of single dose FBZ ASD formulation (2 or 40 mg/kg) was also evaluated and compared against the standard microfilaricide, ivermectin (IVM). Systemic exposures of FBZ/FBZ metabolites achieved following dosing were measured by pharmacokinetic (PK) bioanalysis. At necropsy, five weeks following start of FBZ SC injections, there were significant reductions in burdens of motile O. ochengi worms following multiple injections (93%) or single injection (82%). Further, significant proportions of mice dosed following multiple injections (5/6; 83%) or single injection (6/10; 60%) were infection negative (drug-cured). In comparison, no significant reduction in recovery of motile adult O. ochengi adult worms was obtained in any multiple-oral dosage group. Single oral-dosed FBZ did not mediate any significant microfilaricidal activity against circulating B. malayi mf at 2 or 7 days compared with >80% efficacy of single dose IVM. In conclusion, multiple oral FBZ formulation doses, whilst achieving substantial bioavailability, do not emulate the efficacy delivered by the parenteral route in vivo against adult O. ochengi. PK analysis determined FBZ efficacy was related to sustained systemic drug levels rather than achievable Cmax. PK modelling predicted that oral FBZ would have to be given at low dose for up to 5 weeks in the mouse model to achieve a matching efficacious exposure profile.

Development of a Human iPSC Cardiomyocyte-Based Scoring System for Cardiac Hazard Identification in Early Drug Safety De-risking.

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have emerged as a promising cardiac safety platform, demonstrated by numerous validation studies using drugs with known cardiac adverse effects in humans. However, the challenge remains to implement hiPSC-CMs into cardiac de-risking of new chemical entities (NCEs) during preclinical drug development. Here, we used the calcium transient screening assay in hiPSC-CMs to develop a hazard score system for cardiac electrical liabilities. Tolerance interval calculations and evaluation of different classes of cardio-active drugs enabled us to develop a weighted scoring matrix. This approach allowed the translation of various pharmacological effects in hiPSC-CMs into a single hazard label (no, low, high, or very high hazard). Evaluation of 587 internal NCEs and good translation to ex vivo and in vivo models for a subset of these NCEs highlight the value of the cardiac hazard scoring in facilitating the selection of compounds during early drug safety screening.

Prognostic importance of distressed (Type D) personality and shocks in patients with an implantable cardioverter defibrillator.

BACKGROUND: Clinical trials have shown the benefit of implantable cardioverter defibrillator (ICD) treatment. In this study, we examined the importance of chronic psychological distress and device shocks among ICD patients seen in clinical practice. METHODS: This prospective follow-up study included 589 patients with an ICD (mean age=62.6 ± 10.1 years; 81% men). At baseline, vulnerability for chronic psychological distress was measured by the 14-item Type D (distressed) personality scale. Cox regression models of all-cause and cardiac death were used to examine the importance of risk markers. RESULTS: After a median follow-up of 3.2 years, 94 patients (16%) had died (67 cardiac death), 61 patients (10%) had experienced an appropriate shock and 28 (5%) an inappropriate shock. Inappropriate shocks were not associated with all-cause (p=0.52) or cardiac (p=0.99) death. However, appropriate shocks (HR=2.60, 95% CI 1.47-5.58, p=0.001) and Type D personality (HR=1.85, 95% CI 1.12-3.05, p=0.015) were independent predictors of all-cause mortality, adjusting for age, sex, left ventricular ejection fraction, cardiac resynchronization therapy (CRT), secondary indication, history of coronary artery disease, medication and diabetes. Type D personality and appropriate shocks also independently predicted an increased risk of cardiac death. Other independent predictors of poor prognosis were older age, treatment with CRT and diabetes. CONCLUSION: Vulnerability to chronic psychological distress, as defined by the Type D construct, had incremental prognostic value above and beyond clinical characteristics and ICD shocks. Physicians should be aware of chronic psychological distress and device shocks as markers of an increased mortality risk in ICD patients seen in daily clinical practice.

Emotional distress, positive affect, and mortality in patients with an implantable cardioverter defibrillator.

BACKGROUND: Little is known about the relationship between emotional distress and mortality in patients with an implantable cardioverter defibrillator (ICD). Our aim was to examine the predictive value of general negative and positive affect, and depressive symptoms (including its components somatic symptoms and cognitive-affective symptoms) for mortality. METHODS: ICD patients (N=591, 81% male, mean age=62.7 ± 10.1 years) completed the Global Mood Scale to measure the independent dimensions negative and positive mood, and the Beck Depression Inventory to measure depressive symptoms. Covariates consisted of demographic and clinical variables. RESULTS: During the median follow-up of 3.2 years, 96 (16.2%) patients died. After controlling for covariates, negative affect was significantly related to all-cause mortality (HR=1.034, p=0.002), whereas positive affect was not (HR=1.007, p=0.61). Depressive symptoms were also independently associated with an increased mortality risk (HR=1.031, p=0.030) and somatic symptoms of depression in particular (HR=1.130, p=0.003), but cognitive-affective symptoms were not associated with mortality (HR=0.968, p=0.29). When entering both significant psychological predictors in a covariate-adjusted model, negative mood remained significant (HR=1.039, p=0.009), but somatic symptoms of depression did not (HR=0.988, p=0.78). Similar results were found for cardiac-related death. Of covariates, increased age, CRT, appropriate shocks were positively related to death. CONCLUSIONS: Negative affect in general was related to mortality, but reduced positive affect was not. Depression, particularly its somatic symptoms, was also related to mortality, while cognitive-affective symptoms were not. Future research may further focus on the differential predictive value of emotional distress factors, as well as on mechanisms that relate emotional distress factors to mortality.

Age-related differences in the effect of psychological distress on mortality: Type D personality in younger versus older patients with cardiac arrhythmias.

BACKGROUND: Mixed findings in biobehavioral research on heart disease may partly be attributed to age-related differences in the prognostic value of psychological distress. This study sought to test the hypothesis that Type D (distressed) personality contributes to an increased mortality risk following implantable cardioverter defibrillator (ICD) treatment in younger patients but not in older patients. METHODS: The Type D Scale (DS14) was used to assess general psychological distress in 455 younger (≤70 y, m = 59.1) and 134 older (>70 y, m = 74.3) ICD patients. End points were all-cause mortality and cardiac death after a median follow-up of 3.2 years. RESULTS: Older patients had more advanced heart failure and a higher mortality rate (n = 34/25%) than younger patients (n = 60/13%), P = 0.001. Cardiac resynchronization therapy (CRT), but not Type D personality, was associated with increased mortality in older patients. Among younger patients, however, Type D personality was associated with an adjusted hazard ratio = 1.91 (95% CI 1.09-3.34) and 2.26 (95% CI 1.16-4.41) for all-cause and cardiac mortality; other predictors were increasing age, CRT, appropriate shocks, ACE-inhibitors, and smoking. CONCLUSION: Type D personality was independently associated with all-cause and cardiac mortality in younger ICD patients but not in older patients. Cardiovascular research needs to further explore age-related differences in psychosocial risk.

Shock and patient preimplantation type D personality are associated with poor health status in patients with implantable cardioverter-defibrillator.

BACKGROUND: Implantable cardioverter-defibrillator (ICD) shock is a critical event to patients associated with well-being after implantation, although other factors may play an equally important role. We compared the association of shock and the patient's preimplantation personality with health status, using a prospective study design. METHODS AND RESULTS: Consecutively implanted ICD patients (n=383; 79% men) completed the Type D Scale at baseline and the Short-Form Health Survey 36 (SF-36) at baseline and 3, 6, and 12 months. Of all patients, 23.5% had a Type D personality and 13.8% received a shock during follow-up. Shocked patients reported significantly poorer health status, as did Type D patients. Health status patterns were poorest in patients with combined Type D personality and shock during follow-up. Shock during follow-up was a significant independent associate of poorer health status for 4 of 8 subscales of the SF-36 and the Mental Component Summary (all P<.05), with shocked patients scoring between 2.60 to 13.30 points lower than nonshocked patients. Type D personality was an independent associate of poor postimplantation health status for 6 of 8 of the SF-36 subscales and the Mental Component Summary, with Type D patients scoring between 2.12 to 8.02 points lower, adjusting for demographic and clinical characteristics. CONCLUSIONS: ICD shock and the patient's preimplantation personality disposition were equally important associates of health status 12 months after implantation. Identification of the patient's personality profile before ICD implantation may help identify subsets of patients who may need additional care, for example, with a psychosocial component.

Measuring chronic care management experience of patients with diabetes: PACIC and PACIC+ validation.

BACKGROUND: The patient assessment of chronic illness care (PACIC) is a promising instrument to evaluate the chronic care experiences of patients, yet additional validation is needed to improve its usefulness. METHODS: A total of 1941 patients with diabetes completed the questionnaire. Reliability coefficients and factor analyses were used to psychometrically test the PACIC and PACIC+ (i.e. PACIC extended with six additional multidisciplinary team functioning items to improve content validity). Intra-class correlations were computed to identify the extent to which variation in scores can be attributed to GP practices. RESULTS: The PACIC and PACIC+ showed a good psychometric quality (Cronbach's alpha's >0.9). Explorative factor analyses showed inconclusive results. Confirmative factor analysis showed that none of the factor structures had an acceptable fit (RMSEA>0.10). In addition, 5.1 to 5.4% of the total variation was identified at the GP practice level. CONCLUSION: The PACIC and PACIC+ are reliable instruments to measure the chronic care management experiences of patients. The PACIC+ is preferred because it also includes multidisciplinary coordination and cooperation-one of the central pillars of chronic care management-with good psychometric quality. Previously identified subscales should be used with caution. Both PACIC instruments are useful in identifying GP practice variation.

Too many cohorts and repeated measurements are a waste of resources.

OBJECTIVE: Researchers in Health Sciences and Medicine often use cohort designs to study treatment effects and changes of outcome variables over time period. The costs of these studies can be reduced by choosing an optimal number of repeated measurements over time and by selecting cohorts of subjects more efficiently with optimal design procedures. The objective of this study is to provide evidence on how to design large-scale cohort studies with budget constraints as efficiently as possible. STUDY DESIGN AND SETTING: A linear cost function for repeated measurements is proposed, and this cost function is used in the optimization procedure. For a given budget/cost, different designs for linear mixed-effects models are compared by means of their efficiency. RESULTS: We found that adding more repeated measures is only beneficiary if the costs of selecting and measuring a new subject are much higher than the costs of obtaining an additional measurement for an already recruited subject. However, this gain in efficiency and power is not very large. CONCLUSION: Adding more cohorts or repeated measurements do not necessarily lead to a gain in efficiency of the estimated model parameters. A general guideline for the optimal choice of a cohort design in practice is required and we offer this guideline.

Interactive computer program for optimal designs of longitudinal cohort studies.

Many large scale longitudinal cohort studies have been carried out or are ongoing in different fields of science. Such studies need a careful planning to obtain the desired quality of results with the available resources. In the past, a number of researches have been performed on optimal designs for longitudinal studies. However, there was no computer program yet available to help researchers to plan their longitudinal cohort design in an optimal way. A new interactive computer program for the optimization of designs of longitudinal cohort studies is therefore presented. The computer program helps users to identify the optimal cohort design with an optimal number of repeated measurements per subject and an optimal allocations of time points within a given study period. Further, users can compute the loss in relative efficiencies of any other alternative design compared to the optimal one. The computer program is described and illustrated using a practical example.

D-optimal cohort designs for linear mixed-effects models.

The D-optimality criterion is used to construct optimal designs for different numbers of independent cohorts, which constitute a number of repeated measurements per subject over time. A cost function for longitudinal data is proposed, and the optimality criterion is optimized taking into account the cost of the study. First, an optimal number of design points for a given number of cohorts and cost was identified. Then, an optimal number of cohorts is identified by comparing the relative efficiencies (REs). A numerical study shows that for models describing the trend of a continuous outcome over time by polynomials, the most efficient number of repeated measurements is equal to the sum of the total number of cohorts and the degree of the polynomial in the model. REs of a purely longitudinal cohort design with only one cohort, and mixed longitudinal and cross-sectional cohort designs with more cohorts are compared. The results show that a purely longitudinal cohort design with only one cohort of subjects measured at the optimal time points is the most efficient design. The findings in this paper show that one can obtain a highly efficient design for parameter estimation with only a few repeated measurements. The results of this study will reduce the cost of data collection and ease the logistical burdens in cohort studies.