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PubMed2004

Clinical calibration of DSM-IV diagnoses in the World Mental Health (WMH) version of the World Health Organization (WHO) Composite International Diagnostic Interview (WMHCIDI).

An overview is presented of the rationale, design, and analysis plan for the WMH-CIDI clinical calibration studies. As no clinical gold standard assessment is available for the DSM-IV disorders assessed in the WMH-CIDI, we adopted the goal of calibration rather than validation; that is, we asked whether WMH-CIDI diagnoses are 'consistent' with diagnoses based on a state-of-the-art clinical research diagnostic interview (SCID; Structured Clinical Interview for DSM-IV) rather than whether they are 'correct'. Consistency is evaluated both at the aggregate level (consistency of WMH-CIDI and SCID prevalence estimates) and at the individual level (consistency of WMH-CIDI and SCID diagnostic classifications). Although conventional statistics (sensitivity, specificity, Cohen's kappa) are used to describe diagnostic consistency, an argument is made for considering the area under the receiver operator curve (AUC) to be a more useful general-purpose measure of consistency. In addition, more detailed analyses are used to evaluate consistency on a substantive level. These analyses begin by estimating prediction equations in a clinical calibration subsample, with WMH-CIDI symptom-level data used to predict SCID diagnoses, and using the coefficients from these equations to assign predicted probabilities of SCID diagnoses to each respondent in the remainder of the sample. Substantive analyses then investigate whether estimates of prevalence and associations when based on WMH-CIDI diagnoses are consistent with those based on predicted SCID diagnoses. Multiple imputation is used to adjust estimated standard errors for the imprecision introduced by SCID diagnoses being imputed under a model rather than measured directly. A brief illustration of this approach is presented in comparing the precision of SCID and predicted SCID estimates of prevalence and correlates under varying sample designs.

Adult↗

PubMed2005

Adjusting for partially missing baseline measurements in randomized trials.

Adjustment for baseline variables in a randomized trial can increase power to detect a treatment effect. However, when baseline data are partly missing, analysis of complete cases is inefficient. We consider various possible improvements in the case of normally distributed baseline and outcome variables. Joint modelling of baseline and outcome is the most efficient method. Mean imputation is an excellent alternative, subject to three conditions. Firstly, if baseline and outcome are correlated more than about 0.6 then weighting should be used to allow for the greater information from complete cases. Secondly, imputation should be carried out in a deterministic way, using other baseline variables if possible, but not using randomized arm or outcome. Thirdly, if baselines are not missing completely at random, then a dummy variable for missingness should be included as a covariate (the missing indicator method). The methods are illustrated in a randomized trial in community psychiatry.

Data Interpretation, Statistical↗

PubMed2005

Estimating the proportion of cured patients in a censored sample.

There has been a recurring interest in modelling survival data which hypothesize subpopulations of individuals highly susceptible to some types of adverse events while other individuals are assumed to be at much less risk, like recurrence of breast cancer. A binary random effect is assumed in this article to model the susceptibility of each individual. We propose a simple multiple imputation algorithm for the analysis of censored data which combines a binary regression formulation for the probability of occurrence of an event, say recurrence of the breast cancer tumour, and a Cox's proportional hazards regression model for the time to occurrence of the event if it does. The model distinguishes the effects of the covariates on the probability of cure and on the time to recurrence of the disease. A SAS macro has been written to implement the proposed multiple imputation algorithm so that sophisticated programming effort can be rendered into a user-friendly application. Simulation results show that the estimates are reasonably efficient. The method is applied to analyse the breast cancer recurrence data. The proposed method can be modified easily to accommodate more general random effects other than the binary random effects so that the random effects not only affect the probability of occurrence of the event, but also the heterogeneity of the time to recurrence of the event among the uncured patients.

Algorithms↗

PubMed1989

Estimation of parameters and missing values under a regression model with non-normally distributed and non-randomly incomplete data.

We carried out a simulation study to compare the performance of three algorithms (complete cases, ALLVALUE, and expectation maximization, EM) in estimating regression parameters and missing values for situations that have varying amounts of missing data, distributions (normal, mixture of normals and lognormal), patterns of incomplete data (random, related and censored), and degrees of correlational structure among the dependent and independent variables. We found that the EM and complete cases algorithms performed equally well regardless of the correlational structure, when the percentage of incomplete data was only 5 per cent. When this percentage increased to 25 per cent, the EM algorithm was generally best for estimation, but the complete cases algorithm was safe and conservative. This finding may be attributed to the study design, which required that the slopes be the same in the population of all cases, and in the population of complete cases. In addition, the one-step imputing method (ALLVALUE) was competitive only for situations with weak correlational structure and/or little missing data. In that situation the bias caused with use of all available information was less than that caused with use of only complete cases. On the other hand, for imputation, the EM algorithm performed optimally, even in situations of censored or log-normally distributed data.

Algorithms↗

PubMed1993

Evaluating the effects of tubal sterilization on menstrual function: selected issues in data analysis.

We examined selected issues in data analysis in the Collaborative Review of Sterilization (CREST). CREST is a multicentre, prospective, observational study of women undergoing tubal sterilization. We analysed menstrual function after sterilization in over 5000 women who were enrolled in the period 1978-1983 and followed for 5 years with yearly follow-up interviews. To take into account the dependency among repeated responses from the same individuals, we used the generalized estimating equations (GEE) approach to longitudinal data analysis. Marginal modelling resulted in a statistically significant increase in the odds of menstrual dysfunction at 5 years after tubal sterilization. Transitional modelling produced rates of menstrual dysfunction given a woman's menstrual function at baseline, after adjusting for other baseline characteristics such as method of contraception before sterilization. To examine the direction of the bias that could result from non-random missing data, we refitted our models using imputed values. The models with imputed values showed the same trends as the original models.

Bias↗

PubMed1975

The projection of ocellar neurons within the brain of the locust, Schistocerca gregaria.

Cobalt iontophoresis of the median and lateral ocellar nerves of Schistocerca gregaria, combined with silver impregnated sections of the brain, has demonstrated the projection area of the large and medium-sized ocellar afferent neurons. These neurons terminate within the brain and their cell bodies lie within the protocerebrum. Ocellar neurons project to two discrete areas on each side of the brain, each area receiving input from a different set of fibres. Both postero-dorsal complexes receive an imput from two large ipsilateral and two large median fibres. Their dendritic fields maintain an ordered spatial array relative to one another. The two antero-lateral complexes receive an imput from one large ipsilateral fibre and medium-sized ipsilateral and medium small-field afferent fibres. Each lateral ocellus has two large fibres in common with the median ocellus. These lateromedial fibres receive photoreceptor input from both ocelli but form no major arborisations within the brain. The lateral ocellar tracts appear to form a third ocellar association area since higher-order neurons branch amongst the lateral and latero-medial fibres within the tract. The axons of the higher-order neurons descend to the ventral cord via the circumoesophageal commissures.

Animals↗

PubMed1985

Reliability of adverse drug reaction assessment in psychiatric inpatients.

Within an ongoing drug surveillance program in psychiatric hospitals the applicability of an algorithm for judgment on probability of causal relationship of adverse events and drug therapy was tested. Algorithmic interrater agreement was compared to agreement obtained with the conventional criteria used so far within the program in 80 cases by two raters, who had participated in the drug surveillance program since its beginning in 1979. With the use of the algorithm raters agreed on imputed drugs in 86% of all cases; total agreement on drugs and degree of probability was obtained in 69% (weighted kappa 0.618). Raters agreed on total score for the imputed medication in 49% and also on all subscores for the different axes of the algorithm in 43% of all cases. Differentiation of drug-related from illness-related changes, the use of judgmental terms within the algorithm and specific problems created by the frequent use of combinations of drugs with similar profiles of adverse drug reactions (ADR) in psychiatric patients were identified as the main sources of disagreement. Agreement on total judgment was comparable to results from similar studies in the literature using various algorithms, but in contrast to all these studies a higher percent of agreement (80%) was obtained with the use of the conventional criteria in this study.

Antidepressive Agents↗

PubMed2005

Effectiveness of alendronate and etidronate in the treatment of osteoporosis in men: a prospective observational study.

The prevalence of osteoporosis in men is higher than previously assumed; consequently, numerous therapies are being investigated to treat these patients. The Canadian Database of Osteoporosis and Osteopenia patients (CANDOO) was analyzed to examine changes in bone mineral density (BMD) in consecutively seen osteoporotic men administered alendronate, etidronate or no bone-active drugs (control) over 1 year. A total of 244 men attending six Canadian osteoporosis clinics were included in the study (42 alendronate, 102 etidronate and 100 control). Multiple imputation was used to model missing data to provide a more robust statistical model. The imputed datasets (five) were analyzed using multivariable linear regression to determine differences between groups in the percent change of lumbar spine (LS) and femoral neck (FN) BMD from baseline to 1 year. Differences in the percent change in BMD from baseline were most notable at the LS in favor of alendronate (4.3%; 95% CI: 2.1, 6.6 ) and etidronate (2.1%; 95% CI: 0.3, 4.0) therapy when compared with controls. At the LS, alendronate therapy led to significantly greater (2.2%; 95% CI: 0.2, 4.2) gains in BMD as compared to etidronate therapy. Compared to controls, there were no significant differences in FN BMD with alendronate (2.1%; 95% CI: -0.4, 4.7) or etidronate therapy (0.9%; 95% CI: -1.1, 2.8), nor were there significant differences between bisphosphonate groups (1.3%; 95% CI: -1.1, 3.6, in favor of alendronate). While both alendronate and etidronate significantly increased LS BMD in osteoporotic men after 1 year in real-world settings, alendronate therapy resulted in significantly superior gains in LS BMD. The effect of these two bisphosphonates on fractures and FN BMD in osteoporotic men is likely positive, but requires further study.

Alendronate↗

PubMed2007

Early-life and adult socioeconomic status and inflammatory risk markers in adulthood.

BACKGROUND: Associations between childhood and adult socioeconomic status (SES) and adult levels of inflammatory markers (C-reactive protein [CRP], fibrinogen, white blood cell count [WBC], and von Willebrand factor [vWF]) were examined in the Atherosclerosis Risk in Communities (ARIC) Study cohort. METHODS: A total of 12,681 white and African-American participants provided information on SES (via education and social class) and place of residence in childhood and adulthood. Residences were linked to census data for neighborhood SES information. Multiple imputation was used to impute missing data. Hierarchical and linear regression were used to estimate the effects of SES and possible mediation by adult cardiovascular disease (CVD) risk factors. FINDINGS: Low childhood social class and education were associated with elevated levels of CRP, fibrinogen, WBC, and vWF (increments of 17%, 2%, 4% and 3% for lowest versus highest education in childhood, respectively) among whites. Findings were less consistent among African-Americans. Adult SES was more strongly associated with inflammation than childhood SES. Individual-level SES measures were more consistently associated with inflammation than neighborhood-level measures. Fibrinogen and WBC showed the most consistent associations with SES; the largest changes in inflammation by SES were observed for CRP. Covariate adjustment strongly attenuated these associations. Mediation of the SES-inflammation associations by BMI, smoking and HDL cholesterol (HDL-C) are suggested by these data. CONCLUSION: Low individual- and neighborhood-level SES in childhood and adulthood are associated with modest increments in adult inflammatory burden. These associations may operate through the influence of low SES on traditional CVD risk factors, especially BMI, smoking and HDL-C.

Black or African American↗

PubMed2026

Prognostic modeling of overall survival in metastatic pancreatic cancer: an inflammation-based tool validated in PANTHEIA-SEOM cohort.

PURPOSE: To develop and internally validate the PANTHEIA-SIRI prognostic model, which integrates log-transformed systemic inflammation response index (SIRI) with clinical predictors, to estimate overall survival (OS) in metastatic pancreatic ductal adenocarcinoma (mPDAC) treated with first-line chemotherapy. METHODS: We used data from the multicenter PANTHEIA-SEOM registry. OS was defined from chemotherapy start. The model was fitted as a Weibull accelerated failure time model in the survival-analysis population with multiple imputation. Predictors were log-transformed baseline SIRI, modeled with restricted cubic splines, ECOG, tumor burden, chemotherapy regimen, and anorexia-cachexia syndrome. Internal validation used a separate, non-overlapping cohort from the same registry; the centers contributing to each cohort are listed in a supplementary annex. TRIPOD was followed. Discrimination was assessed with Harrell´s C-index and calibration with IPCW Brier scores and IPA. RESULTS: The derivation cohort comprised 672 patients with SIRI data (593 analyzed for survival) across 22 Spanish hospitals (2015-2025); 80.1% had died after a median OS of 9.9 months. The imputation-pooled derivation C-index was 0.654 (95% CI, 0.627-0.681); optimism-corrected, 0.629. Internal validation used 62 separate patients from the same registry; 96.8% had died after a median OS of 9.2 months. The validation C-index was 0.603 (95% CI, 0.518-0.687). Calibration was adequate at 6 and 12 months. CONCLUSIONS: The PANTHEIA-SIRI model provides individualized OS estimates in mPDAC with routine clinical predictors. Its open-access calculator ( https://pantheia-siri.shinyapps.io/calc/ ) may support prognostic communication, treatment-intensity selection, and supportive-care planning. Routine clinical implementation will require further validation in larger, fully independent cohorts.

Cachexia↗

PubMed1996

An expert system based on causal knowledge: validation on post-cardiosurgical patients.

A new expert system for the analysis of post-cardiosurgical patients in Intensive Care Units is described, and a preliminary validation performed. The inference engine employs a hybrid reasoning method which integrates quantitative and qualitative simulation techniques in an original manner. The long-term knowledge consists of a causal network which reproduces the main relationships between physiological quantities involved in the course after cardiac surgery. Emphasis has been given to respiratory and metabolic, as well as cardiovascular quantities both in the systemic and pulmonary circulations. Preliminary system validation has been performed on a set of 40 cardiosurgical patients, previously classified either at normal-risk (17 patients) or at high-risk (23 patients) by means of statistical classification techniques. In most cases, predictions of the expert system substantially agree with those provided by the more traditional statistical method. The system, however, is also able to furnish detailed explanations on the possible physiological causes responsible for the patient status. In particular, simulation results indicate that a reduction in the cardiac index (19 cases) and an increase in the oxygen utilization coefficient (19 cases) are the most critical alterations in the high-risk patients. The system imputes the reduced cardiac index to a rise in total systemic resistance (15 high-risk patients), a decrease in cardiac strength (2 high-risk patients) or an insufficient filling volume of the systemic circulation (4 high-risk patients). Furthermore, in 6 high-risk patients the depressed cardiac outflow occurs with a reduction in the arterial oxygen content, mainly imputable to an insufficiency of blood hemoglobin content. Finally, two examples of the complete expert system explanatory capabilities are shown with reference to a pair of high-risk patients and discussed.

Blood Circulation↗

PubMedDate not supplied

A conditional bootstrap procedure for reconstruction of the incubation period of AIDS.

Data on the incubation period of AIDS patients are often fragmented and censored. parametric models have been proposed in the literature to impute the missing segment of the incubation period. The numerical results vary widely with the parametric models used. We propose a nonparametric conditional bootstrap (CB) procedure for imputation. The quality of the CB data is studied by checking the asymptotic accuracy of the CB estimators. We establish the asymptotic accuracy of the CB procedure for two basic nonparametric estimators: the empirical distribution function and a kernel-type conditional empirical distribution function. The rates of convergence of the CB approximation are obtained. The results for the kernel-type estimators hold also for the nearest-neighbor-type estimators.

Acquired Immunodeficiency Syndrome↗

PubMed1986

Identification and structure of the gene encoding gpII, a major glycoprotein of varicella-zoster virus.

The genome of varicella-zoster virus (VZV) encodes three major families of glycoproteins (gpI, gpII, and gpIII). mRNA from VZV-infected cells was hybrid selected using a library of VZV recombinant plasmids and translated in vitro; polypeptide products were immunoprecipitated by polyclonal monospecific guinea pig antibodies to gpII. The mRNA encoding a 100-kD polypeptide precipitable by anti-gpII antibodies mapped to the HindIII D fragment near the center of the UL region. DNA sequence analysis of this region of the VZV genome revealed a 2.6-kbp open reading frame (ORF) potentially encoding a 98-kDa polypeptide possessing the characteristics of a glycoprotein. The 100-kDa polypeptide was specified by mRNA isolated by hybrid selection using a plasmid containing part of the 2.6-kbp ORF, and immunoprecipitation of this protein by anti-gpII antibodies and by convalescent zoster serum was blocked specifically by purified gpII. We conclude that the 2.6-kbp ORF encodes gpII. The imputed primary amino acid sequence of gpII shows a high degree of homology to that of herpes simplex virus type 1 (HSV-1) gB, a result consistent with the equivalent map locations of the respective genes in the HSV and VZV genomes and with the recently reported serological cross-reactivity of HSV-1 gB and VZV gpII. Unlike the mature gene products of gB, those of gpII have been described as a pair of glycoproteins with approximate molecular weights of 60 kDa in reducing gels, products of a single glycoprotein species with approximate mol mass of 125-140 kDa in nonreducing gels. Amino-terminal sequences of purified gpII were determined and compared to the imputed amino acid sequence. This comparison implies that the primary translational product is cleaved approximately into halves in vivo and suggests that mature gpII is a disulfide-linked heterodimer.

Amino Acid Sequence↗

PubMedDate not supplied

Parental representations of neurotic and endogenous depressives.

Low parental care and parental overprotection have been incriminated as risk factors to depression in adult life. The relevance of these parental characteristics to broad depressive 'types' with their varying imputed aetiologies was assessed by having 26 patients with endogenous depression (ED) and 40 with neurotic depression (ND) complete the Parental Bonding Instrument (PBI) self-report measure. In comparison to their controls, the EDs did not differ on the parental care and overprotection scales. The NDs, by contrast, were more likely than their controls to report their parents as uncaring and overprotective. A PBI care scale score of less than 10 was particularly discriminating, being reported by 3.8% of the EDs and 37.5% of the NDs. While findings support the binary view of depression in terms of broad imputed aetiological factors, several response biases which might influence the findings are considered.

Adult↗

PubMed1994

Disability, stigma and deviance.

An important contribution social science research makes to understanding the experiences of disabled individuals in the U.S. is to illuminate the influence of stigma and deviance on those experiences. Because perceptions of negative difference (deviance) and their evocation of adverse responses (stigma) have been and continue to be widespread, it is these with which alternate perceptions and responses vie in the construction of disability's symbolic and practical meanings. While some research demonstrates a regrettable imposition of stigma/deviance into the lives and minds of disabled people, some of it shows disabled people resisting stigma/deviance imputations; and some of it suggests that such imputations are losing force as new ways of thinking about the meaning of disability gain sway.

Attitude to Health↗

PubMed1994

Maturity of human immunodeficiency virus infection and incubation period of acquired immunodeficiency syndrome in injecting drug users.

This study was aimed at estimating the maturity of the human immunodeficiency virus (HIV) epidemic in cohorts of injecting drug users with existing HIV infection at the time of first observation, and using this information to estimate the incubation period of acquired immunodeficiency syndrome (AIDS) in this population group. The method imputed the "missing" time from seroconversion to first observation for seroprevalent subjects in a combined cohort including injecting drug users from New York (n = 246) and Baltimore (n = 621). Imputation relied on a probability model predicting time since seroconversion on the basis of two markers of maturity of HIV infection: percent of CD4+ lymphocytes and platelet count. The model was developed from data observed in a combined cohort of subjects from New York (n = 24) and Baltimore (n = 112) who had incident HIV infections. The estimates of median time since seroconversion for the Baltimore and Bronx seroprevalent subcohorts were 28 and 39 months, respectively. The total time from seroconversion to AIDS was then estimated for the incident plus completed-prevalent cohorts using a modified version of the nonparametric product-limit method. The results showed that approximately 95% (95% confidence interval: 90 to 98%) of drug users remained AIDS-free 2 years after seroconversion; 83% (74-91%), 4 years after seroconversion; and 72% (61-82%), 6 years after seroconversion. Median time to AIDS was 10.2 years, with an estimated 95% confidence interval of 7.9 to 12.3 years. Consistency of these results with those derived from large cohorts of homosexual men indicate that the HIV incubation distributions for drug users and homosexual men are similar.

Acquired Immunodeficiency Syndrome↗

PubMed2005

Follow-up difficulty: correlates and relationship with outcome in heroin dependence treatment in the NEPOD study.

Data collected from 317 heroin users who participated in four studies that were included in the Australian National Evaluation of Pharmacotherapies for Opioid Dependence were analysed to examine predictors of follow-up difficulty and whether follow-up difficulty was related to heroin use outcomes. Participants who were no longer receiving treatment were more difficult to contact and more likely to be lost to follow-up. Participants treated in general practice settings were also more difficult to contact and more likely to be lost to follow-up than participants treated at specialist clinics. Contact difficulty among followed-up participants (either in or out of treatment) was unrelated to heroin use outcomes. The 21% of participants who were followed-up with just one contact attempt reported 20.0 heroin-free days in the previous month, increasing only slightly to 20.9 based on the 70% of participants eventually contacted after up to 20 attempts. The study examined three methods for imputing missing heroin use outcome data and concluded that imputation of missing outcome data by inserting corresponding baseline data may be too conservative.

Adolescent↗

PubMed2026

Efficacy and safety of deucravacitinib, an oral, selective tyrosine kinase 2 inhibitor, in patients with active psoriatic arthritis: 52-week results from the randomised, double-blind, placebo-controlled phase 3 POETYK PsA-1 trial.

OBJECTIVES: The randomised, double-blind, placebo-controlled, phase 3 Program fOr Evaluation of TYK2 inhibitor Psoriatic Arthritis-1 (POETYK PsA-1) trial evaluated the efficacy, safety, and tolerability of deucravacitinib, an oral, selective tyrosine kinase 2 inhibitor, in patients with PsA naïve to biologic disease-modifying antirheumatic drugs. METHODS: Adults with active PsA, high-sensitivity C-reactive protein concentration ≥ 3 mg/L, and ≥ 1 PsA-related hand and/or foot erosion detectable via radiograph were randomised 1:1 to oral deucravacitinib 6 mg once daily or placebo through week (W) 16. At W16, patients continued receiving deucravacitinib or switched from placebo to deucravacitinib through W52. The primary endpoint was American College of Rheumatology 20% improvement in response (ACR20) at W16. Nonresponder imputation was used for missing data. Efficacy and safety were evaluated through W52. Post hoc rank analysis of covariance was used to evaluate structural damage with no missing data imputation. RESULTS: In 670 patients, a significantly greater proportion of those receiving deucravacitinib vs placebo achieved ACR20 at W16 (54.2% vs 34.1%, P < .001). Responses with deucravacitinib were increased at W52. Patients who switched from placebo to deucravacitinib achieved improvements similar to those in patients who received continuous deucravacitinib. Inhibition of structural damage was observed at W16 and W52. At W16, incidences of serious adverse events (AEs) (deucravacitinib, 1.8%; placebo, 2.4%) and discontinuations due to AEs (2.4%; 1.8%) were low and remained low through W52, without imbalances in cardiovascular events, malignancies, or opportunistic infections. No new safety signals were detected; no deaths occurred. CONCLUSIONS: Deucravacitinib demonstrated superiority vs placebo for clinical responses, patient-reported outcomes, and structural damage inhibition in patients with PsA, with favourable tolerability and safety.

Humans↗