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PubMed1999

Validity of family history data on essential tremor.

BACKGROUND: In family studies of essential tremor (ET), valid data on the presence of ET in relatives of probands with ET is important. The family history method uses information obtained by interviewing probands with ET to identify ET in their relatives. The validation of this method by direct examination of the relatives has not been performed. OBJECTIVE: To determine the validity of family history data on ET in families in which the proband has ET. METHODS: ET cases (probands) and their respective relatives were enrolled in a genetic study of ET in Washington Heights-Inwood, New York. Each underwent a tremor interview and videotaped examination. Two neurologists rated the severity of tremor and assigned diagnoses (ET versus normal). Probands were asked to identify their relatives who had ET. The validity of the probands' responses was tested against the neurologists' diagnoses. RESULTS: There were 206 subjects: 46 ET cases and 160 relatives. Twelve (7.5%) of 160 relatives were diagnosed with ET (four definite ET and eight probable ET). Probands with ET reported that two of these 12 had tremor (sensitivity of probands' report = 16.7%). Six of the 12 affected relatives (50.0%) reported their own tremor. The probands reported that one of 136 of their unaffected relatives had tremor (specificity of probands' report = 99.3%). CONCLUSIONS: For family studies of ET, information on reportedly unaffected relatives is of limited use given the low sensitivity of family history data. The neurologic examination remains the only valid means of ascertaining cases of ET among relatives.

Aged↗

PubMed1996

Development and validation of the European League Against Rheumatism response criteria for rheumatoid arthritis. Comparison with the preliminary American College of Rheumatology and the World Health Organization/International League Against Rheumatism Criteria.

OBJECTIVE: To validate the European League Against Rheumatism (EULAR), the American College of Rheumatology (ACR), and the World Health Organization (WHO)/International League Against Rheumatism (ILAR) response criteria for rheumatoid arthritis (RA). METHODS: EULAR response criteria were developed combining change from baseline and level of disease activity attained during follow up. In a trial comparing hydroxychloroquine and sulfasalazine, we studied construct (radiographic progression), criterion (functional capacity), and discriminant validity. RESULTS: EULAR response criteria had good construct, criterion, and discriminant validity, ACR and WHO/ILAR criteria showed only good criterion validity. CONCLUSION: EULAR response criteria showed better construct and discriminant validity than did the ACR and the WHO/ILAR response criteria for RA.

Adult↗

PubMed1995

Reliability and validity of the CSSRD functional assessment survey in rheumatoid arthritis. Cooperative Systematic Studies of Rheumatic Diseases.

OBJECTIVE: To demonstrate the reliability and validity characteristics of a fast, intensively focused functional assessment questionnaire that has been used in rheumatoid arthritis clinical trials by the Cooperative Systematic Studies of Rheumatic Diseases group (CSSRD). METHODS: Data from three double-blind, controlled clinical trials by CSSRD were used to examine the properties of the Functional Assessment Survey as a measure of physiologic function. RESULTS: The Functional Assessment Survey has reasonable test-retest reliability and convergent validity with the Steinbrocker et al. functional class. It demonstrated appropriate divergent validity with other clinical measures of response, as well as discriminant validity. CONCLUSIONS: The CSSRD Functional Assessment Survey is brief, intensive, and focused. Reliability and validity characteristics have been documented.

Activities of Daily Living↗

PubMed1998

Validation of questionnaire-based response criteria of treatment efficacy in the fibromyalgia syndrome.

OBJECTIVE: To compare the validity of self-reported questionnaires as response criteria of treatment efficacy in patients with fibromyalgia syndrome. METHOD: At the beginning of the treatment period, 70 fibromyalgia patients, randomly allocated to electro-acupuncture or placebo, underwent a clinical evaluation by rheumatologists and answered 1) a generic quality of life questionnaire--the Psychological General Well-Being Index (PGWB), 2) a specific function and symptom questionnaire, and 3) a pain questionnaire--the Regional Pain Score (RPS). The same evaluation was repeated at the end of the treatment period. Severity of the condition was assessed by a composite outcome score, a combination of different clinical outcome measures forming a clinical severity index. The variations between these questionnaire scores before and after treatment and the variations between the clinical severity indices estimated by clinicians were used as measures of the treatment impact. The first rationale for the validation was a positive correlation between clinical and questionnaire score changes. Another rationale for validation of the new instruments was the ability to identify the different treatment interventions. RESULTS: The correlation between the clinical severity index and the RPS was good (r = 0.62). Moreover, the RPS demonstrated a good discriminant power in detecting patients with effective treatment: it showed a specificity of 74% and a sensitivity of 75%. The PGWB correlated less well with the clinical score and was less discriminant. The specific function and symptom questionnaire showed little additional validity. CONCLUSIONS: Outcomes of syndrome severity such as pain and subjective well-being, as measured by self-reported questionnaires, can be valid instruments to evaluate treatment efficacy in short-term clinical trials. In the current study, the RPS proved to be particularly useful to assess the widespread tenderness of fibromyalgia and demonstrated high discriminative power.

Activities of Daily Living↗

PubMed2001

The cognitive decline scale of the psychogeriatric assessment scales (PAS): longitudinal data on its validity.

OBJECTIVE: The Cognitive Decline scale of the Psychogeriatric Assessment Scales (PAS)1 uses informant data to assess retrospectively change from earlier in life. Data from a 7-8-year longitudinal study were used to assess the validity of this scale against changes in cognitive performance and mortality. DESIGN AND MEASURES: PAS data were collected on three occasions, with gaps of 3.6 and 4.1 years between the waves. The Cognitive Decline score at Wave 3 was validated retrospectively against actual change on a brief test of current cognitive status (the PAS Cognitive Impairment scale) over the three waves, while the Cognitive Decline score at Wave 1 was assessed for predictive validity against future mortality and cognitive change. SETTING: A community survey in the Australian cities of Canberra and Queanbeyan. PARTICIPANTS: Participants were aged 70+ at the beginning of the study. The sample size varied from 729 to 279, depending on the number of waves involved. RESULTS: Participants with scores of 4+ on the Cognitive Decline scale at Wave 3 showed substantial deterioration over the previous 7-8 years. Scores of 4+ at Wave 1 predicted mortality and further cognitive deterioration. CONCLUSIONS: The Cognitive Decline scale allows a valid retrospective assessment of change and has predictive validity for subsequent cognitive deterioration and increased mortality.

Aged↗

PubMed1999

Is serum bilirubin concentration the only valid prognostic marker in primary biliary cirrhosis?

From the many prognostic models for primary biliary cirrhosis (PBC) patients based on Cox's regression analysis, the Mayo model has gained the most popularity and was successfully validated in some centers. The aim of our study was to validate the Mayo survival model for Polish PBC patients and, in case of its inapplicability, to select prognostic variables and to create time-fixed and time-dependent survival models for the patients. We used database information on patients from 6 medical centers in Poland, fulfilling clinical, serological, and/or pathological criteria of PBC. The Mayo model was validated using data from 116 PBC patients. The time-fixed and time-dependent models were created using data on clinical and biochemical variables used in the Mayo model from 162 and 208 patients, respectively. The Mayo model validation was performed graphically and by one-sample log-rank tests after dividing the study sample into 3 groups of high, medium, and low risk. The survival analysis was performed using Cox's proportional hazards regression method on clinical and biochemical variables used in the Mayo model. Treatment with ursodeoxycholic acid (UDCA) was included in the time-dependent analysis. Validation showed that the Mayo model overestimated death risk in Polish PBC patients. Of the variables used in the Mayo model, serum bilirubin concentration appeared to be the only variable of prognostic importance. The analysis shows that serum bilirubin concentration holds most of the prognostic information for our PBC patients irrespective of prior treatment with UDCA.

Bilirubin↗

PubMed2006

Nonsynonymous SNPs: validation characteristics, derived allele frequency patterns, and suggestive evidence for natural selection.

We experimentally investigated more than 1,200 entries in dbSNP that would change amino-acids (nsSNPs), using various subsets of DNA samples drawn from 18 global populations (approximately 1,000 subjects in total). First, we mined the data for any SNP features that correlated with a high validation rate. Useful predictors of valid SNPs included multiple submissions to dbSNP, having a dbSNP validation statement, and being present in a low number of ESTs. Together, these features improved validation rates by almost 10-fold. Higher-abundance SNPs (e.g., T/C variants) also validated more frequently. Second, we considered derived alleles and noted a considerably (approximately 10%) increased average derived allele frequency (DAF) in Europeans vs. Africans, plus a further increase in some other populations. This was not primarily due to an SNP ascertainment bias, nor to the effects of natural selection. Instead, it can be explained as a drift-based, progressive increase in DAF that occurs over many generations and becomes exaggerated during population bottlenecks. This observation could be used as the basis for novel DAF-based tests for comparing demographic histories. Finally, we considered individual marker patterns and identified 37 SNPs with allele frequency variance or FST values consistent with the effects of population-specific natural selection. Four particularly striking clusters of these markers were apparent, and three of these coincide with genes/regions from among only several dozen such domains previously suggested by others to carry signatures of selection.

Alleles↗

PubMedDate not supplied

Validation of a vertical visual analogue scale as a measure of clinical dyspnea.

The purpose of this study was to validate a vertical visual analogue scale (VVAS) as a measure of clinical dyspnea. Concurrent validity was demonstrated by having asthmatics score their dyspnea intensity on both a VVAS and a horizontal visual analogue scale (HVAS), and then measuring their peak expiratory flow rate (PEFR). Correlation between the VVAS and HVAS was r = .97; between the VVAS and the PEFR, correlation was r = -.85, demonstrating the concurrent validity of the VVAS as a measure of dyspnea. Construct validity then was established, using the contrasted-groups approach with repeated measures. Both asthmatics and those with chronic obstructive lung disease (COPD) rated their dyspnea on the VVAS during times of severe and little airway obstruction. The dyspnea ratings at times of severe versus low obstruction were found to be different for both the asthmatic and COPD subjects. The VVAS was shown to have both concurrent and construct validity as a measure of dyspnea.

Asthma↗

PubMed1991

Validation of an immunoradiometric assay to measure plasma levels of active renin.

An immunoradiometric assay (IRMA) for active renin in human plasma was analytically and clinically validated. Analytical validation established 1) precision, 2) recovery, 3) linearity, 4) cross-reactivity, 5) sample stability, and 6) the validity and specificity of the 125I-labeled anti-renin monoclonal in the Diagnostics Pasteur immunoradiometric renin kit. Clinical validation included 1) establishing normal reference range for renin, 2) comparing plasma renin activity (PRA) results to immunoreactive renin levels in subjects on Upjohn research protocols, and 3) comparing the renin responsiveness of sodium replete subjects to that of sodium deplete subjects prior to, during, and after infusion with Upjohn renin inhibitory peptide, ditekiren. This study was undertaken to demonstrate the research validity of an assay tool for the differentiation of enzymatically active renin from inactive renin or a form of prorenin.

Autoradiography↗

PubMed1996

Musculoskeletal Function Assessment instrument: criterion and construct validity.

The Musculoskeletal Function Assessment (MFA) instrument, a health status instrument with 100 self-reported health items, was designed for use with the broad range of patients with musculoskeletal disorders of the extremities commonly seen in clinical practice. In this paper, we report on its criterion and construct validity. Criterion validity was tested against physicians' ratings of patient functioning (e.g., upper functioning, lower functioning, daily activities, recreational functioning, emotional adjustment, and overall functioning) and standard clinical measures (e.g., grip strength, walking speed, fine motor skills, knee and elbow strength, and range of motion). Significant correlations (p < or = 0.05) between its scores, physicians' ratings, and clinical measures support the MFA's criterion validity. Construct validity was demonstrated against existing measures of health status (e.g., measures of lower and upper mobility, activity level and satisfaction, health status, social support, pain, emotional status, and quality of life), in accordance with clinical hypotheses about the effect of musculoskeletal disorders on functioning (e.g., type and number of problems, severity of illness or injury, and comorbidities) and by an analysis of demographic characteristics (e.g., sex, education, income, health insurance, and employment) against the MFA scores. Discriminant construct validity was supported in an analysis of MFA scores by patient disease groups (p < or = 0.01).

Adolescent↗

PubMed2005

Once-a-day extended-release dosage form of divalproex sodium III: development and validation of a Level A in vitro-in vivo correlation (IVIVC).

Defining a quantitative and reliable relationship between in vitro drug release and in vivo absorption is highly desired for rational development, optimization, and evaluation of controlled-release dosage forms and manufacturing process. During the development of a once-daily extended-release (ER) tablet of divalproex sodium, a predictive in vitro drug release method was designed and statistically evaluated using three formulations with varying release rates. In order to establish an internally and externally validated Level A IVIVC, a total of five different ER formulations of divalproex sodium were used to evaluate a linear IVIVC model based on the in vitro test method. For internal validation, a single-dose four-way crossover study (N = 16) was performed using fast-, medium-, and slow-releasing ER formulations and a 12-h IV infusion of valproic acid as reference. To validate the IVIVC externally, a second three-way crossover study (N = 36) was performed using slightly-fast-, medium-, and slightly-slow-releasing ER formulations. The in vivo absorption-time profile was inferred by deconvolution of the observed plasma concentration-time profiles against the unit disposition function (UDF). A linear IVIVC model was established in which the in vivo absorption was expressed as a function of in vitro drug release. Plasma profiles of ER formulations were estimated via convolution of in vitro release profiles with the UDF. Successful internal and external validations of the model were demonstrated by individual and average absolute percent prediction errors of </=9% for both C(max) and AUC(infinity). In conclusion, a Level A IVIVC describing the entire time-course of plasma concentrations was developed and validated, both internally and externally, for ER formulations of divalproex sodium.

Adolescent↗

PubMed2001

Reliability and validity of a new global dyskinesia rating scale in the MPTP-lesioned non-human primate.

Behavioral rating scales for dyskinesia in the non-human primate are frequently used to assess the efficacy of new treatments and to provide a clinical correlative with neurochemical and neuropathological changes. Although a large variety of different scales have been used in non-human primate studies, there is no single standardized scale, and none have been evaluated for reliability and validity. We are reporting a new global non-human primate dyskinesia rating scale (GPDRS) for the squirrel monkey, developed in the context of an independent study of dyskinesia. In this report we demonstrate the reliability and validity of this scale. The GPDRS is a single-item scale with well-defined points and brevity allowing for rapid and easy application for assessing the overall degree of dyskinesia. In this study, seven MPTP-lesioned and four non-lesioned (control) non-human primates were videotaped following treatment with either levodopa or water. To test inter- and intra-rater reliability, three examiners rated the videotape independently at two different time points and these assessments were compared. The validity of the scale was tested in two phases. First, examiners rated the videotape using the GPDRS and the Abnormal Involuntary Movement Scale (AIMS), a scale commonly used to rate dyskinesia in the non-human primate, and the ratings from each scale were compared. Second, validity was tested in the context of an independent dyskinesia study, in which the scale was used to distinguish between two treatment groups. The GPDRS was shown to have high inter- and intra-rater reliability and to be valid for the assessment of dyskinesia in the squirrel monkey. In this report we also demonstrate the inter- and intra-rater reliability of the AIMS.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed2005

Validity of a modified Parkinson's disease screening questionnaire in India: effects of literacy of participants and medical training of screeners and implications for screening efforts in developing countries.

The prevalence of Parkinson's disease (PD) is low among Indians, except in the Parsis. Data for Indians come from studies using different screening tools and criteria to detect PD. An epidemiological study in India, which has nearly a billion people, more than 18 spoken languages, and varying levels of literacy, requires development and validation of a screening tool for PD. The objectives of this study are to (1) validate a modified version of a widely used screening questionnaire for PD to suit the needs of the Indian population; (2) compare the use of a nonmedical assistant (NMA) with the use of a medical person during screening; and (3) compare the effect of literacy of participants on the validity of the screening tool. The validity of the questionnaire was tested on 125 participants from a home for the elderly. NMAs of similar background and medical personnel administered the modified screening questionnaire. A movement disorder neurologist blind to the responses on the questionnaire, examined participants independently and diagnosed if participants had PD. The questionnaire was validated in the movement disorders clinic, on known PD patients and their family members without PD. In the movement disorders clinic, sensitivity and specificity of the questionnaire were 100% and 89%, respectively. Fifty-seven participants were included for analysis. The questionnaire had a higher sensitivity when NMAs (75%) rather than the medical personnel (61%) administered it, and its specificity was higher with the medical personnel (61%) than with NMAs (55% and 25%). The questionnaire had a higher specificity in literates than illiterates, whereas sensitivity varied considerably. The modified questionnaire translated in a local Indian language had reasonable sensitivity and can be used to screen individuals for PD in epidemiological studies in India. This questionnaire can be administered by NMAs to screen PD and this strategy would reduce manpower costs. Literacy may influence epidemiological estimates when screening PD.

Aged↗

PubMed2005

The development and initial validation of the Terminally Ill Grief or Depression Scale (TIGDS).

Patients often experience 'preparatory-grief' as they cope with the dying process. Some may be depressed. The Terminally Ill Grief or Depression Scale (TIGDS), comprising grief and depression sub-scales, is a new self-report measure designed to differentiate between preparatory-grief and depression in adult inpatients. The initial 100-item inventory was assembled based on literature review, interviews with clinicians and dying patients and then shortened to 42 items based on consensus expert opinion. Validity and reliability were tested in a sample of 55 terminally ill adults. The consensus clinical opinion was used as the gold standard to differentiate between preparatory grief and depression. The intra-class correlation coefficient was high (it was calculated to estimate the test-retest reliability for the 47 patients who had completed the TIGDS twice--retest was administered 2 to 7 days after the initial test), ranging from 0.86 (grief) to 0.97 (depression). The validity of TIGDS was assessed using a receiver operating characteristic curve analysis, comparing the first test with the clinical criterion. The first and only variable and cut-point was the depression score (chi-square = 18.4, p < 0.001, cut point = 3). The sensitivity of the TIGDS was 0.727 and specificity was 0.886 for the depression = 3 cutoff score. The construct validity of the TIGDS was tested by comparing with the Hospital Anxiety and Depression Scale (HADS). The TIGDS depression subscale showed strong convergent validity and the TIGDS grief subscale showed strong discriminant validity with the HADS total score.

Aged↗

PubMed2004

Validity and reliability of a questionnaire to measure the impact of lower urinary tract symptoms on quality of life: the Leicester Impact Scale.

AIMS: To develop a condition specific quality of life measure for males and females with urinary storage symptoms of urgency, frequency, nocturia and incontinence. MATERIALS AND METHODS: A sample of community dwelling males and females aged 40 years or more who were taking part in an epidemiological study provided data for development and validation of the scale. Questions were developed from literature review and discussions with clinicians and patients. Inclusion of items was dependent on levels of missing data and principal components analysis. Validity was assessed by comparison with the Hospital Anxiety and Depression Scale, the Bradburn Negative Affect Scale and single questions concerning the problematic nature of symptoms. Construct validity was assessed by comparing cases and non-cases, and patients with different symptom patterns. Test-retest and inter-rater reliability statistics were calculated for individual items. Responsiveness to change was measured in subjects taking part in a randomised controlled trial of a nursing intervention. RESULTS: The scale showed high levels of internal consistency and measures of construct validity were as hypothesised. Test-retest and inter-rater reliability was moderate to excellent. The distribution of scores was skewed with low levels of impact but the questionnaire was responsive to conservative treatments in patients receiving a nursing intervention. CONCLUSIONS: The questionnaire proved to be a valid and reliable interviewer administered instrument for measuring impact of urinary symptoms.

Aged↗

PubMed2006

Targeted proteomics in biomarker validation: detection and quantification of proteins using a multi-dimensional peptide separation strategy.

Authentic biomarkers, distilling the essence of a complex, functionally significant process in a mammalian system into a precise, physicochemical measurement have been implicated as a tool of increasing importance for drug discovery and development. However, even in spite of recent technological advances, validating a new biomarker candidate, where generation of suitable antibodies is required, is still a long-lasting task. Methods to accelerate initial validation by MS approaches have been suggested, but all methods described so far are associated with serious drawbacks, finally leading to non-generic methods of detection and quantification. Moreover, when complex body fluids are used as samples, efficient debulking strategies are crucial to open a window of analytical sensitivity in the ng/mL range, where many diagnostically relevant analytes are present. Here we report the proof-of-principle of a multi-dimensional strategy for accelerated initial validation of biomarker candidates by MS, which promises to be generally applicable, sensitive and quantitative. The method presented employs a combination of electrophoretic and chromatographic steps on the peptide level, followed by MS quantification using isotopically labeled synthetic peptides as internal standards. Our proposed workflow includes up to four dimensions, finally resulting in a desired LOD sufficient to detect and quantify diagnostically relevant analytes from complex samples. Although the current state of the method only represents a starting point for further validation and development, it reveals great potential in biomarker validation.

Animals↗

PubMed2004

Estimating vaccine efficacy using auxiliary outcome data and a small validation sample.

In vaccine studies, a specific diagnosis of a suspected case by culture or serology of the infectious agent is expensive and difficult. Implementing validation sets in the study is less expensive and is easier to carry out. In studies using validation sets, the non-specific or auxiliary outcome is measured on each participant while the specific outcome is measured only for a small proportion of the participants. Vaccine efficacy, defined as one minus some measure of relative risk, could be severely attenuated if based only on the auxiliary outcome. Applying missing data analysis techniques could thus correct the bias while maintaining statistical efficiency. However, when the sample size in the validation sets is small and the vaccine is highly efficacious, all specific outcomes are likely to be negative in the validation set in the vaccinated group. Two commonly used missing data analysis methods, the mean score method and multiple imputation, depend on the ad hoc continuity correction when none of the specific outcomes are positive and the normality or log-normality assumption of relative risk, which may not hold when the relative risk is highly skewed, to estimate the confidence interval. In this paper, we propose a Bayesian method to estimate vaccine efficacy and its highest probability density (HPD) credible set using Monte Carlo (MC) methods when using auxiliary outcome data and a small validation sample. Comparing the performance of these approaches using data from a field study of influenza vaccine and simulations, we recommend to use the Bayesian method in this situation.

Adolescent↗

PubMed2000

Cross-Validation Methods.

This paper gives a review of cross-validation methods. The original applications in multiple linear regression are considered first. It is shown how predictive accuracy depends on sample size and the number of predictor variables. Both two-sample and single-sample cross-validation indices are investigated. The application of cross-validation methods to the analysis of moment structures is then justified. An equivalence of a single-sample cross-validation index and the Akaike information criterion is pointed out. It is seen that the optimal number of parameters suggested by both single-sample and two-sample cross-validation indices will depend on sample size. Copyright 2000 Academic Press.

Journal Article↗