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PubMed2001

The COMS randomized trial of iodine 125 brachytherapy for choroidal melanoma, II: characteristics of patients enrolled and not enrolled. COMS Report No. 17.

OBJECTIVES: To describe characteristics of patients evaluated for the Collaborative Ocular Melanoma Study (COMS) randomized clinical trial of iodine 125 brachytherapy for choroidal melanoma by enrollment status, and to compare characteristics of patients enrolled with those of patients with tumors of eligible size who did not enroll in order to assess the extent to which findings from the clinical trial can be generalized to future patients. METHODS: For all patients diagnosed with choroidal melanoma and evaluated for the clinical trial at COMS centers from November 1986 through July 31, 1998, selected data were transmitted to the COMS Coordinating Center, Baltimore, Md, where they were integrated and analyzed. Data included ophthalmic and medical history, examination findings, and visual acuity measurements recorded prior to enrollment; standardized A- and B-scan echographic examination findings; and wide-angle fundus photographs and fluorescein angiograms. RESULTS: Of 8712 patients with choroidal melanoma, 5046 had tumors of eligible size; of these, 2882 (57%) were eligible for enrollment, and 1317 (46% of eligible patients, 26% of patients with tumors of eligible size) enrolled. Most differences between eligible and ineligible patients corresponded to eligibility and exclusion criteria. However, ineligible patients were older and had thicker tumors than eligible patients. Eligible patients who enrolled were slightly older and had larger tumors than those who did not enroll. Nearly half (48%) of enrolled patients had choroidal melanoma with the apex located temporal to the fovea, compared with 40% of eligible patients not enrolled and 29% of ineligible patients. CONCLUSIONS: This trial was designed to yield internally valid treatment comparisons through random assignment to treatment at time of enrollment. Information from this and other studies document that enrolled patients were similar to other patients with choroidal melanoma who were treated with 125I brachytherapy. These findings support the external validity of the trial and applicability of treatment findings to all patients who meet the criteria used to judge eligibility for the trial.

Adult↗

PubMed1990

The literature on personality disorders, 1985-88: trends, issues, and controversies.

This review of the recent literature on personality disorders summarizes theoretical and methodologic issues, DSM-III-R criteria sets, nosological controversies, and current treatment approaches. Work in the personality disorders is burgeoning, with increasing attention to improved reliability and validity of diagnosis. Investigators are looking at such issues as the development of dimensional taxonomies, the effect of state variables, the problem of diagnostic overlap, the effect of comorbid conditions on course and treatment, the predictive power of criteria, and external validators. The DSM-III-R criteria sets, despite their polythetic format, may be no more reliable than their predecessors. Because treatment remains largely unresearched, the clinician must continue to rely on skillful assessment of each patient, with psychoanalytic psychotherapy and symptom-oriented drug trials providing the foundation of therapy.

Humans↗

PubMed2002

Comparative molecular field analysis of substrates for an aryl sulfotransferase based on catalytic mechanism and protein homology modeling.

Comparative Molecular Field Analysis (CoMFA) methods were used to produce a 3D-QSAR model that correlated the catalytic efficiency of rat hepatic aryl sulfotransferase (AST) IV, expressed as log(k(cat)/K(m)), with the molecular structures of its substrates. A total of 35 substrate molecules were used to construct a CoMFA model that was evaluated on the basis of its leave-one-out cross-validated partial least-squares value (q(2)) and its ability to predict the activity of six additional substrates not used in the training set. The model was constructed using substrate conformations that favored (1) proton abstraction by the catalytic histidine residue, (2) an in-line sulfuryl-group transfer mechanism, and (3) constraints imposed by the residues lining the substrate binding pocket of a homology model of AST IV. This CoMFA model had a q(2) value of 0.691, and it successfully predicted the activities of the six molecules not used in the training set. A final CoMFA model was constructed using the same methodology but with molecules from both the training set and the test set. Its q(2) value was 0.701, and it had a non-cross-validated r(2) value of 0.922. The contour coefficient map generated by this CoMFA was overlaid on the amino acids in the substrate-binding pocket of the homology model of AST IV and found to show a good fit. Additionally external validation was obtained by using the CoMFA model to design substrates that show high activities. These results establish a methodology for prediction of the substrate specificity of this sulfotransferase based on CoMFA methods that are guided by both the homology model and the catalytic mechanism of the enzyme.

Animals↗

PubMed2004

[Prediction of aerobic fitness without stress testing and applicability to epidemiological studies: a systematic review].

Cardiorespiratory fitness is used as an independent factor for evaluating risk of all-cause mortality, but mainly from coronary heart disease. Nevertheless, evaluation of fitness based on stress tests poses numerous epidemiological difficulties. Alternative forms of evaluation have therefore been suggested using non-exercise-based regression models. This study aimed to analyze these models and their applicability to epidemiological studies. A systematic review was conducted of articles published from 1966 to 2002. The models were classified according to: (a) theoretical justification for the explanatory variables included in the model; (b) validation criteria (gold standard); (c) regression models fully reported, including standard error of estimation; and (d) cross-validation. The search process yielded 23 studies, five of which met all established quality criteria. The authors conclude that cardiorespiratory evaluation by non-exercise-based models could be feasible in epidemiological studies. However, few equations appear to meet the minimum external validation requirements to provide data that could be generalized to large populations.

Adolescent↗

PubMed1995

The clinical boundaries of posttraumatic stress disorder.

Three sets of clinical boundaries exist for posttraumatic stress disorder (PTSD), as for all concepts of psychiatric disorder. The first involves the border with normal psychology in general, and with the normal psychology of stress response in particular. This boundary can be surveyed from a number of vantage points and the maps which result will not necessarily correspond. The second boundary issue involves internal boundaries between psychiatric disorders, specifically between PTSD and other concepts of disorder. The high level of comorbidity documented in PTSD has ensured that this aspect of boundary setting is particularly contentious. The third set of boundaries is concerned with subtyping within the global construct of PTSD. The validity and extent of subtyping would be based on the degree to which phenomenological differences exist in relation to PTSD syndromes occurring in the wake of certain types of traumatic events. Such clinical subtyping might however need to be buttressed by external validity indicators such as differential treatment responses or outcome. A final boundary issue of major significance to therapists involves the need to place oneself unambiguously on the side of the trauma survivor in the struggle to resolve the traumatic experiences. The pivotal position of PTSD in the psychopathological arena is discussed.

Adaptation, Psychological↗

PubMed2005

Validity and reliability of an Italian version of the revised Leeds disability questionnaire for patients with ankylosing spondylitis.

OBJECTIVE: The purpose of the present study was to produce an Italian version of the Revised Leeds Disability Questionnaire (LDQ) in a group of patients with ankylosing spondylitis, and to examine the psychometric properties of this version, evaluating its internal consistency, external validity and reliability. METHODS: The LDQ was administered to 60 Caucasian patients affected by ankylosing spondylitis (50 males, 10 females, mean age 46.1 +/- 14.2 yr, range 22-74, median disease duration 4.5 yr, range 1-24) together with the Italian version of the Stanford Health Assessment Questionnaire (HAQ), and anthropometric measurements. Thirty patients completed the questionnaire after a 10-day interval. Internal consistency was evaluated with Cronbach's alpha coefficient of reliability. Construct validity of the LDQ was evaluated using the correlation between the HAQ and anthropometric measurements. Test-retest reliability was assessed with the intraclass correlation coefficient. RESULTS: All patients completed the validation study. The questionnaire was internally consistent (alpha=0.90). A significant correlation was recorded between the LDQ and the HAQ score (rho=0.841, P<0.01) and the anthropometric measurements. Test-retest reliability showed a good correlation coefficient (intraclass correlation=0.97). CONCLUSION: The Italian LDQ is a valid and reliable instrument for detecting and measuring functional disability in patients with ankylosing spondylitis. Our results confirm the utility of this questionnaire as a valid and feasible functional measure for patients with ankylosing spondylitis.

Adult↗

PubMed1992

Development and validation of a logistic regression-derived algorithm for estimating the incremental probability of coronary artery disease before and after exercise testing.

OBJECTIVES: Our goals were to develop and validate a multivariate algorithm for estimating the incremental probability of the presence of coronary artery disease. BACKGROUND: Multivariate methods, including logistic regression analysis, have been extensively applied to diagnostic exercise testing. However, few previous studies have included both an incremental design and external validation. METHODS: A retrospective collection of clinical, exercise test and catheterization data was performed involving four U.S. referral medical centers. All patients had no prior history of coronary disease and had undergone coronary angiography < or = 3 months after exercise stress testing. An algorithm was developed in one center (590 patients with a 41% prevalence of coronary artery disease) with the use of logistic regression analysis and was validated in the other three centers (1,234 patients, 70% prevalence). The algorithm incorporated pretest variables (age, gender, symptoms, diabetes, cholesterol), exercise electrocardiographic (ECG) variables (mm of ST segment depression, ST slope, peak heart rate, metabolic equivalents [METs], exercise angina) and one thallium variable. Discrimination was measured with receiver operating characteristic curve analysis. Calibration (that is, reliability) was assessed from a comparison of probability estimates and the actual prevalence of disease. RESULTS: The overall incremental receiver operating characteristic curve areas for the validation group were pretest, -0.738 +/- 0.016; postexercise ECG, 0.78 (SE 0.017); and postthallium, 0.82 (SE 0.016); p < 0.01 for both increments. Within the three validation institutions, the institution with a disease prevalence closest to that of the derivation institution had the best incremental receiver operating characteristic curve areas. There was a stepwise incremental improvement in calibration especially from exercise ECG to thallium testing. CONCLUSIONS: An incremental multivariate algorithm derived in one center reliably estimated disease probability in patients from three other centers. The incremental value of testing was best demonstrated when the derivation and validation groups had a similar disease prevalence. This algorithm may be useful in decision making that relates to the diagnosis of coronary disease.

Algorithms↗

PubMed1993

The impact of response frequency on the Rorschach constellation indices and on their validity with diagnostic and MMPI-2 criteria.

I first examined the effects of response frequency (R) on the Comprehensive System's constellation indices (Exner, 1991). R is significantly associated with 26 of the 29 constellation criteria that are based on raw numbers and significantly correlated with total scores on each of the constellations. I then examined how R impacts the external validity of the constellations. The ability of the Schizophrenia Index and the Suicide Constellation to discriminate diagnostic groups appears to be impaired when protocols deviate from average length, whereas the Hypervigilance Index (HVI) appears most diagnostic of a paranoid condition when it is relatively elevated in brief records. R also clearly mediates the relationship between the Rorschach and Minnesota Multiphasic Personality Inventory-2 (MMPI-2) criteria. In lengthy protocols, many of the cross-method convergent correlations between appropriate MMPI-2 scales and the Depression Index, Obsessive Style Index, and HVI are quite high and approach the maximum found in personality research. In brief protocols, there are strong negative correlations between these constellations and self-reports of depression and interpersonal distress. Implications from these findings for the integration of assessment methods are discussed.

Adaptation, Psychological↗

PubMed1989

The cumulative structure of personal and instrumental ADL. A study of elderly people in a health service district.

Katz' Index of ADL has been supplemented by five well-defined instrumental activities, namely cooking, washing, transportation, cleaning, and shopping. Eighty-five persons, mainly elderly, who had consecutively consulted a district occupational therapist, were assessed in their homes in order to study the reliability, the scalability, and the validity of the expanded index. The inter-observer reliability was high. The coefficient of scalability was well above the acceptance level, indicating construct validity. No person was dependent in personal ADL and totally independent in instrumental ADL. Persons who were dependent in both personal and instrumental ADL were older and lived in sheltered accommodation more often than persons who were dependent only in instrumental ADL, indicating external validity. This study shows that there was a cumulative relationship between certain well-defined instrumental activities and between personal and instrumental activities. This supplemented index can be useful for assessing and differentiating the need for personal assistance and homecare among disabled elderly people.

Activities of Daily Living↗

PubMed2006

Single subject controlled experiments in aphasia: the science and the state of the science.

UNLABELLED: This paper discusses the use of single subject controlled experimental designs for investigating the effects of treatment for aphasia. A brief historical perspective is presented, followed by discussions of the advantages and disadvantages of single subject and group approaches, the basic requirements of single subject experimental research, and crucial considerations in design selection. In the final sections, results of reviews of published single subject controlled experiments are discussed, with emphasis on internal validity issues, the number of participants enrolled in published studies, operational specification of the dependent and independent variables, and reliability of measurement. LEARNING OUTCOMES: As a result of reading this paper, the participant will: (1) understand the mechanisms required for demonstration of internal and external validity using single subject controlled experimental designs, (2) become familiar with the basic requirements of single subject controlled experimental research, (3) understand the types of single subject controlled experimental designs that are the most appropriate for studying the effects of treatment for aphasia, and (4) become familiar with trends in the published aphasia treatment literature in which single subject controlled experimental designs have been used.

Aphasia↗

PubMed2001

Examining the validity of pressure ulcer risk assessment scales: developing and using illustrated patient simulations to collect the data.

Simulations are of particular advantage in research studies where large samples are necessary to achieve statistical power and the information must be collected under uniform conditions in order to aid interpretation. In the study reported below, simulation was achieved through the use of medical photography accompanied by case studies of the same patients. All information was collected on the same day. The purpose of the study was to determine the validity of the three pressure ulcer risk assessment scales most commonly used in clinical nursing practice in the UK. Each clinical nurse assessed the same four patients using three risk assessment scales and a visual analogue scale designed to capture their own clinical judgement. External validity was assessed by a panel of tissue viability experts who provided independent ratings. Data were obtained from 236 clinical nurses, yielding 941 risk assessments. Experience with this approach to data collection suggests that it requires careful planning. This should include measures to ensure that the simulated information is valid and that all data collectors have been adequately trained and are able to motivate the nurses participating in the study. Providing consideration is given to these issues, the use of simulation can help to collect data that would be difficult to obtain by more conventional means. It is also important to recognize that clinical decisions are de-contextualized in simulations because they are reduced to verbal and visual summaries. The decision to use simulations should thus be taken only if this is acknowledged.

Clinical Competence↗

PubMed1993

Testing the effects of nutrient deficiencies on behavioral performance.

The association between specific nutrient deficiencies and poor performance on behavioral tests has been documented for several nutrients. The determination of causality, however, remains elusive. This paper presents the essential criteria for a valid test of causality. Findings from experimental studies in which a nutritional treatment was randomly allocated can be summarized in a statistical statement about the probability that the nutrient treatment caused the behavioral response. Criteria for assessing the internal validity of these studies are examined in terms of whether alleviation of a nutrient deficiency did or did not produce a detectable behavioral response. The plausibility of such a causal inference is dependent on its congruency with known or theorized biological and behavioral mechanisms. External validity describes the extent to which inferences from internally valid studies may be applicable to other populations or circumstances. In addition to these scientific considerations, some of the ethical issues of nutrient-treatment trials are also discussed. All of these considerations provide a better basis for judging whether public health action would be worthwhile than do observed associations that could actually be due to other causes.

Behavior↗

PubMed2005

Development and validation of a perioperative satisfaction questionnaire.

BACKGROUND: Satisfaction is considered a valuable measure of outcome of healthcare processes. Only a few anesthesia-related validated questionnaires are reported. Because their scope is restricted to specific clinical contexts, their use remains limited. The objective of the current study was to develop and validate a self-reported questionnaire, Evaluation du Vecu de l'Anesthesie Generale (EVAN-G), assessing the satisfaction of the perioperative period surrounding general anesthesia. METHODS: Development of the EVAN-G questionnaire comprised a phase of item generation and a phase of psychometric validation. The patient sample was generated to be proportionally matched to the population of patients undergoing general anesthesia in France. The structure of the questionnaire was identified studying interitem, item-dimension, and interdimension correlations and factor analyses. Data were concurrently gathered to assess external validity. The discriminant validity was determined by comparison of scores across well known patient groups. Reliability was assessed by computation of Cronbach alpha coefficients and by test-retest. RESULTS: Eight hundred seventy-four patients were recruited in eight anesthesia departments. The EVAN-G includes 26 items; six specific scores and one global index score are available. Correlations between EVAN-G scores and other concurrent measures supported convergent validity. The EVAN-G correlated poorly with age, American Society of Anesthesiologists physical status, total anesthesia time, and number of previous anesthesias. Significantly higher satisfaction was reported by patients older than 65 yr, belonging to the laryngeal mask group. Reliability and reproducibility were shown. CONCLUSION: The EVAN-G adds important information oriented toward patients' perceptions. The authors' approach provides a novel, valid, and reliable tool that may be used in anesthesia practice.

Adult↗

PubMed2005

Efficacy and effectiveness approaches in behavioral treatment trials.

The objective is to clarify the distinction between efficacy and effectiveness approaches and to discuss how these approaches can be used in a complementary way in the development, evaluation, and implementation of behavioral treatments for primary headache in various settings. Efficacy studies, with an emphasis on internal validity, are experiments that evaluate treatment response in an ideal, highly controlled research environment. Despite their methodological strengths, efficacy studies are limited in their ability to estimate the treatment effects that can be expected in clinical practice settings. Effectiveness studies, with an emphasis on external validity, are outcome studies with less controls that evaluate treatment response in settings more representative of clinical practice. Effectiveness studies, however, are limited in their ability to determine the causal link between treatment and response. Based on the four-phase model used in new drug development, a three-phase linear progression model is presented for behavioral treatment studies. This model provides for pilot testing, efficacy testing, and effectiveness testing of behavioral treatments so that there is appropriate evaluation from initial promise of a developing treatment to implementation and dissemination to various treatment delivery settings.

Behavior Therapy↗

PubMed1995

Increasing response rates in telephone surveys: a randomized trial.

BACKGROUND: Sampling frames and mode of contact and administration of questionnaires are important factors contributing to response rates and selection bias in population-based research. The purpose of this paper is to evaluate whether contact by mail before contact by telephone increases response rate, and to assess the concurrent validity of telephone surveys for collecting health research and service data. METHODS: Two thousand households were randomly selected from electronic white pages. Half were randomly allocated to receive or not to receive an explanatory letter before telephone contact. Interviewers were blinded to whether a household received a letter. Respondents aged 18 years or over were randomly selected from within each household using a Kish grid and interviewed by telephone. RESULTS: The overall response rate was 68 per cent [confidence interval (CI) 66-70]. The response rate of those who received the letter was 76 per cent (CI 73-79), and of those who did not receive the letter was 60 per cent (CI 56-63). Use of the Kish grid to select randomly a respondent decreased the response rate by less than 10 per cent. The internal validity of the data was as follows: in a 10 per cent sub-sample, the Kish grid had been correctly applied in 93 per cent of households, and in 99 per cent of households the exclusion criteria had been correctly adhered to. The external validity was as follows: comparisons with data obtained from the same reference population using similar instruments administered face-to-face revealed no meaningful or significant differences in population estimates. CONCLUSIONS: Mail-out before telephone contact greatly increases response rates at low cost. Telephone surveys can yield valid, useful data for health research and service evaluation.

Adult↗

PubMedDate not supplied

Chain melting temperature estimation for phosphatidyl cholines by quantum mechanically derived quantitative structure property relationships.

Geometries for 62 phosphatidylcholines (PC) were optimized using the AM1 semiempirical quantum mechanical method. Results obtained from these calculations were used to calculate 463 descriptors for each molecule. Quantitative Structure Property Relationships (QSPR) were developed from these descriptors to predict chain melting temperatures (Tm) for the 41 PCs in the training set. After screening each QSPR for statistical validity, the Tm values predicted by each statistically valid QSPR were compared to corresponding Tm values extracted from the literature. The most predictive, chemically meaningful QSPR provided Tm values which agreed with literature values to within experimental error. This QSPR was used to predict Tm values for the remaining 21 PCs to provide external validation for the model. These values also agreed with literature values to within experimental error. The descriptor developed by the final QSPR was the second order average information content, a topological information-theoretical descriptor.

Calorimetry, Differential Scanning↗

PubMed2001

A multivariable model for predicting the need for blood transfusion in patients undergoing first-time elective coronary bypass graft surgery.

BACKGROUND: The incidence of blood transfusion in coronary artery bypass graft (CABG) surgery remains high. Preoperative identification of those at high risk for requiring blood will allow for the cost-effective use of some blood conservation modalities. Multivariable analysis techniques were used in this study to develop a prediction rule for such a purpose. STUDY DESIGN AND METHODS: Data were prospectively collected for all patients undergoing elective first-time CABG surgery from January 1997 to September 1998 at a tertiary-care teaching hospital (n = 1007). The prediction rule was developed on the first two-thirds of the sample by using logistic regression methods to examine the relationship of patient demographics, comorbidities, and preoperative Hb with perioperative blood transfusion. The remaining one-third of the sample was used to validate the rule. RESULTS: The transfusion rate was 29.4 percent. The prediction rule included preoperative Hb (g/dL, OR 0.928, p<0.0001), weight (kg, OR 0.938, p<0.0001), age (years, OR 1.037, p<0.01), and sex (male/female, OR 0.493, p<0.01); receiver operating characteristic = 0.86. When externally validated, the rule had a sensitivity of 82.1 percent and a specificity of 63.6 percent (at a selected probability cutoff). CONCLUSION: A simple and valid prediction rule is developed for predicting the risk of blood transfusion in patients undergoing first-time elective CABG surgery.

Aged↗

PubMed2026

Integrated multi-omics profiling of amniotic fluid identifies predictive biomarkers for fetal growth restriction trajectories.

BACKGROUND: Fetal growth restriction (FGR) is a complex condition with highly heterogeneous clinical outcomes, making prenatal distinction between transient and persistent growth failure challenging. This study aims to identify amniotic fluid (AF) biomarkers capable of differentiating distinct FGR trajectories and characterizing persistent growth failure mechanisms. METHODS: Integrated proteomic and metabolomic profiling was performed on AF samples from transient FGR (n = 11), persistent FGR (n = 9), and healthy controls (n = 13). Diagnostic and prognostic models were developed using multivariate analysis. Selected protein candidates were validated via ELISA in an independent cohort (n = 69). RESULTS: Multi-omics analysis revealed distinct molecular signatures for FGR stratification. A two-protein diagnostic panel (PDGFA and phospho-STAT5A) achieved an AUC of 1.000 in the discovery stage and 0.780 in the external validation cohort. For prognostic assessment, a molecular signature including IREB2, HLA-C, and PLXNB2 accurately predicted persistent growth failure from transient recovery (AUC = 0.966). Cross-platform integration highlighted the mass spectrometry-derived WASHC2C as a central hub protein with a significant progressive increase across the control, transient, and persistent groups (p < 0.001). CONCLUSIONS: This study establishes a multi-omics framework for prenatal FGR stratification. Our findings identify distinct molecular signatures reflecting the intrauterine environment and provide high-performance molecular tools for predicting divergent fetal growth trajectories to guide personalized clinical decision-making.

Humans↗