SEARCH · PubMed Health

Results for “Internal validation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources

PubMed1997

[Translation and validation of the questionnaire "Tinnitus Handicap Questionnaire, 1990].

OBJECTIVE: The Tinnitus Handicap Questionnaire (THQ) measures subjective tinnitus handicap in terms of emotional, social, and health impact (factor 1), hearing (factor 2), and perception of tinnitus (factor 3). A French version of the THQ was used with 178 tinnitus sufferers in ENT consultation. Internal validity was confirmed by correlations between (i) semigroups of items (Cronbach's alpha), (ii) item and total scores, and (iii) individual items, for each factor (Pearson's r), and was found to be strong (alpha = .90). All items (except 25 and 26) showed strong total-score correlations (.30 < or = r < or = .74). All factor 1 items intercorrelated strongly (.34 < or = r < or = .70). The factor 2 axis was coherent, with interitem correlations between .46 and .74, and its concurrent validation in strong factor 2 items correlations with hearing loss, if any (multiple linear regression: r = .67, p < .0001). Moreover, hearing-impaired (mean = 44.47 +/- 31.13) and normal-hearing (mean = 15.2 +/- 21.10) factor 2 scores were significantly different. CONCLUSION: As with the original THQ, factor 3 items were not strongly intercorrelated; moreover, items 25 and 26 failed to correlate with total score, suggesting that factor 3 is to be regarded with great caution.

Adolescent↗

PubMedDate not supplied

Designing naturalistic prospective studies of economic and effectiveness outcomes associated with novel antipsychotic therapies.

The cornerstone of recent pharmacoeconomic work in schizophrenia is the hypothesis that the improved efficacy of novel antipsychotic medications will lead to a reduction in medical services utilization, thereby reducing direct medical costs associated with treatment. Creating the most valid design to prospectively examine the effectiveness and costs of competing pharmacotherapies requires a dialectic of opposing research paradigms. The final protocol must represent a series of decisions that strike a careful balance between being scientifically sound (internal validity) and generalizable to the real world of clinical treatment (external validity). The results must be useful to decision-makers in determining to what extent reductions in healthcare expenditures can offset higher drug acquisition costs within their type of treatment environment. This article is a review of several methodological challenges in the design of medical effectiveness trials, including whether to blind the study, definition of the patient population, degree of physician discretion in treatment, and how to collect and analyze data for patients who discontinue their originally assigned medication. The article also provides a discussion of how clinical practices can inform decisions made to meet these challenges. The issues are illustrated through a prospective study designed to evaluate the cost-effectiveness of the newer antipsychotics in general and olanzapine in particular. Cost-effectiveness studies of novel antipsychotic medications, particularly those with naturalistic designs, will increase in importance as the use of these second-generation agents continues to expand.

Antipsychotic Agents↗

PubMedDate not supplied

Is there evidence for early mobilization following an extraarticular hand fracture?

The authors conducted a systematic review to determine if there is scientifically valid (level I or II) evidence for the effect of early motion (<21 days) of joints surrounding an extraarticular hand fracture on fracture healing or functional outcomes. Two reviewers independently evaluated for study inclusion, trial quality and internal validity. Six poor-quality, quasirandomized studies (level III evidence) involving 459 patients were included. Findings suggest that in simple, closed metacarpal fractures, early motion (EM) has the potential to: (1) result in earlier recovery of mobility and strength, (2) facilitate an earlier return to work, and (3) not affect fracture alignment. Findings also indicate that skin pressure problems are not associated with custom-molded metacarpal fracture braces. The scientific validity of EM interventions after an extraarticular hand fracture has not been established in well-conducted, randomized, controlled trials (level I or II evidence). Current evidence does not support or refute the use of EM after an extraarticular hand fracture. However, further investigations are warranted, as findings to date show a consistent potential for benefit with no significant risk of harm when early regional joint motions are incorporated into the management of closed, extraarticular, finger metacarpal fractures.

Early Ambulation↗

PubMed2006

[Bioequivalence assessment of pioglitazone hydrochloride oral preparation by limited sampling strategy].

AIM: To develop limited sampling strategy (LSS) for estimation of C(max) and AUC(0-t) and assessing the bioequivalence of two pioglitazone hydrochloride (PGT) preparations. METHODS: Healthy subjects (n = 20), enrolled in a bioequivalence study, were received 30 mg PGT po of reference or test formulation. The plasma concentration of PGT was determined by the validated HPLC method. A multiple linear regression analysis of the Cmax and AUC(0-t) against the PGT concentration for the reference formulation was carried out to develop LSS models to estimate these parameters. The models were internally validated by the Jackknife method and externally validated using simulated sets generated by Monte Carlo method. The best model was employed to assess bioequivalence of the two PGT formulations. RESULTS: The linear relationship between pharmacokinetics parameters and single concentration point was poor. Several models for these parameters estimation met the predefined criteria (r2 > 0.9). The Jackknife validation procedure revealed that LSS models based on two sampling times (C1, C2.5 and C1.5, C2.5 for C(max); C1.5, C9 and C2.5, C9 for AUC(0-t) predict accurately. Mean prediction errors (MPE) were less than 3%, and mean absolute prediction error (MAE) were less than 9%. The prediction error (PE) beyond 20% was less than 5% of total samples. Model external validation by Monte Carlo simulated data indicated that the most informative sampling combinations were C1.5, C2.5 for C(max), and C1.5, C9 for AUC(0-t), respectively. MPE and MAE of the proposed models were less than 5% , and 9% respectively. The PE beyond 20% was less than 5% of the total. Bioequivalence assessment of the two PGT formulations, based on the best LSS models, provided results similar to those obtained using all the observed concentration-time data points, and indicated that the two PGT formulations were bioequivalent. CONCLUSION: The LSS method for bioequivalence assessment of PGT formulations was established and proved to be applicable and accurate. Thus, it could be considered appropriate for PGT bioequivalence study with inexpensive cost of sampling acquisition and analysis. Key words: pioglitazone hydrochloride; limited sampling strategy; Monte Carlo simulation; bioequivalence

Administration, Oral↗

PubMed1990

Assessing threats to the validity of experimental and observational designs.

Experimental designs, particularly the randomized trial, are viewed as the most scientifically rigorous methods by which knowledge is attained. Most clinical disciplines, however, use observational study designs more frequently than experimental designs. Nevertheless, the scientific rigor of experimental designs can be approximated by observational designs if common internal validity threats are recognized and addressed during the development of the research protocol. This paper presents a model of threats that can be applied to both types of designs to compare their scientific merits.

Case-Control Studies↗

PubMed2006

Development and validation of the Chinese version of the Diabetes Management Self-efficacy Scale.

OBJECTIVE: The purpose of this study was to translate the Diabetes Management Self-Efficacy Scale (DMSES) into Chinese and test the validity and reliability of the instrument within a Taiwanese population. RESEARCH DESIGN AND METHODS: A two-stage design was used for this study. Stage I consisted of a multi-stepped process of forward and backward translation, using focus groups and consensus meetings to translate the 20-item Australia/English version DMSES to Chinese and test content validity. Stage II established the psychometric properties of the Chinese version DMSES (C-DMSES) by examining the criterion, convergent and construct validity, internal consistency and stability testing. The sample for Stage II comprised 230 patients with type 2 diabetes aged 30 years or more from a diabetes outpatient clinic in Taiwan. RESULTS: Three items were modified to better reflect Chinese practice. The C-DMSES obtained a total average CVI score of .86. The convergent validity of the C-DMSES correlated well with the validated measure of the General Self-Efficacy Scale in measuring self-efficacy (r=.55; p<.01). Criterion-related validity showed that the C-DMSES was a significant predictor of the Summary of Diabetes Self-Care Activities scores (Beta=.58; t=10.75, p<.01). Factor analysis supported the C-DMSES being composed of four subscales. Good internal consistency (Cronbach's alpha=.77 to .93) and test-retest reliability (Pearson correlation coefficient r=.86, p<.01) were found. CONCLUSIONS: The C-DMSES is a brief and psychometrically sound measure for evaluation of self-efficacy towards management of diabetes by persons with type 2 diabetes in Chinese populations.

Analysis of Variance↗

PubMed2004

Tree and spline based association analysis of gene-gene interaction models for ischemic stroke.

In the biology of complex disorders, such as atherothrombosis, interactions among genetic factors may play an important role, and theoretical considerations suggest that gene-gene interactions are quite common in such diseases. We used a nested case-control sample from the Physicians' Health Study, a randomized trial assessing the effects of aspirin and beta-carotene on cardiovascular disease and cancer among 22071 US male physicians, to examine these relationships for ischemic stroke. Data were available on 92 polymorphisms from 56 candidate genes related to inflammation, thrombosis and lipid metabolism, assessed in 319 incident cases of ischemic stroke and 2090 disease-free controls. We used classification and regression trees (CART) and multivariate adaptive regression spline (MARS) models to explore the presence of genetic interactions in these data. These models offer advantages over typical logistic regression methods in that they may uncover interactions among genes that do not exhibit strong marginal effects. Final models were selected using either the Bayes Information Criterion or cross-validation. Model fit was assessed using 10-fold cross-validation of the entire selection process. Both the CART and two-way MARS-logit models identified an interaction between two polymorphisms linked to inflammation, the P-selectin (val640leu) and interleukin-4 (C(582) T) genes. Internal validation of these models, however, suggested that effects of these polymorphisms are additive. Although further external validation of these models is necessary, these methods may be valuable in exploring and identifying potential gene-gene as well as gene-environment interactions in association studies.

Adult↗

PubMed1999

Identification of responders to a therapy: an example of validation of a predictive model.

The general objective of randomized clinical trials is to assess if the treatment effect on a given population is clinically meaningful. In this way, one obtains an average estimate of the treatment effect over the trial population. However, a growing need for medical practitioners is to be able to predict with sufficient precision the efficiency of a given treatment for a given patient. There is little information in the literature about this issue. We have previously proposed a treatment-startified Cox model including interaction between treatment and patient's covariates, to identify and predict the responders to a therapy. In this paper, we focus on the assessment of the predictive power of the model. The performance of the predictive model for a population and for an individual was statistically validated internally and externally from several aspects. The prediction correlates well with the observation. Thus, we suggest that this approach would be useful in identifying and predicting the responders to a therapy, subject to an appropriate and more extensive validation process in real setting.

Female↗

PubMed2001

Relevance of clonogenic assays in hematotoxicology.

Clonogenic assays have been established in hematology for 30 years. They have been widely used in fundamental studies on hematopoiesis and they are also routinely used in clinical hematology to confirm diagnosis or to predict time to recovery in cases of bone marrow failure. Their use in toxicological studies is more recent. Adverse effects of xenobiotics can induce hematological problems and pathologies such as neutropenia, thrombocytopenia, anemia, and aplastic anemia. Three clonogenic assays are proposed for granulopoiesis, megakaryopoieisis and erythropoieisis. Hematopoietic progenitors from murine or human origin can be cultured in the presence of xenobiotics using validated protocols to complete standard animal toxicological studies. These clonogenic assays can help to predict adverse effects of drugs or toxicants. Clonogenic assays using white blood cell progenitors (CFU-GM culture) have recently been validated by ECVAM and can be used routinely. Megakaryocyte progenitor (CFU-MK) culture is under development and prevalidation in toxicological studies supported by ECVAM. Red blood cells progenitor culture (BFU-E) has been proposed but needs international validation to be recognized.

Animals↗

PubMed2006

Risk equation determining unsuccessful cannulation events and failure to maturation in arteriovenous fistulas (REDUCE FTM I).

Fistulas are the preferred permanent hemodialysis vascular access but a significant obstacle to increasing their prevalence is the fistula's high "failure to mature" (FTM) rate. This study aimed to (1) identify preoperative clinical characteristics that are predictive of fistula FTM and (2) use these predictive factors to develop and validate a scoring system to stratify the patient's risk for FTM. From a derivation set of 422 patients who had a first fistula created, a prediction rule was created using multivariate stepwise logistic regression. The model was internally validated using split-half cross-validation and bootstrapping techniques. A simple scoring system was derived and externally validated on 445 different, prospective patients who received a new fistula at five large North American dialysis centers. The clinical predictors that were associated with FTM were aged > or =65 yr (odds ratio [OR] 2.23; 95% confidence interval [CI] 1.25 to 3.96), peripheral vascular disease (OR 2.97; 95% CI 1.34 to 6.57), coronary artery disease (OR 2.83; 95% CI 1.60 to 5.00), and white race (OR 0.43; 95% CI 0.24 to 0.75). The resulting scoring system, which was externally validated in 445 patients, had four risk categories for fistula FTM: low (24%), moderate (34%), high (50%), and very high (69%; trend P < 0.0001). A preoperative, clinical prediction rule to determine fistulas that are likely to fail maturation was created and rigorously validated. It was found to be simple and easily reproducible and applied to predictive risk categories. These categories predicted risk of FTM to be 24, 34, 50, and 69% and are dependent on age, coronary artery disease, peripheral vascular disease, and race. The clinical utility of these risk categories in increasing rates of permanent accesses requires further clinical evaluation.

Adolescent↗

PubMed2003

[Predicted functional outcome 100 days after ischemic strokes: design of a prospective study about the external validation of a prognostic model].

The purpose of this study is to externally validate previously developed prognostic models predicting functional outcome 100 days after acute ischaemic stroke. Data prospectively collected from 1,754 patients were used to develop two models predicting functional dependence (Barthel Index < 95) and mortality. Both models were internally validated and calibrated. A prospective multicentre study is being performed to validate the developed models with an independent data set. On admission to one of 15 participating hospitals, all patients with acute ischaemic stroke will be registered prospectively in the co-ordinating centre. Within 72 hours, potential predictive variables will be assessed. 1,975 patients will have to be recruited to achieve a power of 95% at the 5% significance level. The resulting prognostic models will be useful for adequately stratifying treatment groups in clinical trials and to accurately predicting the outcome variable.

Brain Ischemia↗

PubMed2005

Renal blood flow measurements with use of phase-contrast magnetic resonance imaging: normal values and reproducibility.

PURPOSE: To assess the validity and the direct, short-term, and long-term reproducibility of renal blood flow (RBF) measurements with phase-contrast (PC) magnetic resonance (MR) imaging. MATERIALS AND METHODS: In 20 healthy volunteers, RBF measurements were repeated with and without repositioning. Internal validity was assessed by comparing the total RBF with the difference in aortic flow above and below the renal arteries. In 19 healthy volunteers, RBF measurements were performed at two different occasions. In 40 healthy volunteers, RBF measurements were performed to assess normal values as a function of age. Analyses were performed according to Bland and Altman. RESULTS: The technical success rate ranged from 78% to 85%. Total RBF and the difference in aortic flow rates showed good agreement (Pearson correlation coefficient, 0.72; P = .002). Directly repeated measurements had a mean difference of 54 mL/min in total RBF with a coefficient of variation (CV) of 17%. For repeated measurements with repositioning, the mean difference in total RBF was 74 mL/min (CV, 23%). Repeated measurements on different occasions showed a CV of 20%. The mean total RBF of the 40 healthy volunteers was 838 mL/min +/- 244 (SD). CONCLUSIONS: RBF measurement with PC MR has a success rate greater than 75%. The demonstrated internal reliability of this method and fair reproducibility of the flow parameters is crucial for further studies of the renal artery with MR imaging.

Adult↗

PubMed2000

A method for quantification of absolute amounts of nucleic acids by (RT)-PCR and a new mathematical model for data analysis.

Accurate quantification of nucleic acids by competitive (RT)-PCR requires a valid internal standard, a reference for data normalization and an adequate mathematical model for data analysis. We report here an effective procedure for the generation of homologous RNA internal standards and a strategy for synthesizing and using a reference target RNA in quantification of absolute amounts of nucleic acids. Further, a new mathematical model describing the general kinetic features of competitive PCR was developed. The model extends the validity of quantitative competitive (RT)-PCR beyond the exponential phase. The new method eliminates the errors arising from different amplification efficiencies of the co-amplified sequences and from heteroduplex formation in the system. The high accuracy (relative error <2%) is comparable to the recently developed real time detection 5'-nuclease PCR. Also, corresponding computer software has been devised for practical data analysis.

Cell Line↗

PubMed2001

Psychometric properties of a Spanish version of the McGill Pain Questionnaire in several Spanish-speaking countries.

OBJECTIVE: Versions of the McGill Pain Questionnaire are available in a several languages and are used in clinical studies and sociocultural or ethnic comparisons of pain issues. However, there is a lack of studies that compare the validity and reliability of the instrument in the countries where it is used. The current study investigates the psychometric properties of a Spanish version of the McGill Pain Questionnaire in five Spanish-speaking countries. DESIGN: The authors conducted a multicenter and transnational study with one investigator in each center. Patients were evaluated once with a Spanish version of the McGill Pain Questionnaire, a visual analog scale, and a verbal rating scale. SETTING: The study was performed in pain clinics and acute pain units of four Latin American countries (Argentina, Costa Rica, Mexico, and Panama) and Spain. PATIENTS: The study included 205 patients (84 with acute pain, 121 with chronic pain) from Latin America. Their data were compared with those of 282 Spanish patients. INTERVENTIONS: The McGill Pain Questionnaire, visual analog scale, and verbal rating scale were administered once to all patients. The McGill Pain Questionnaire was administered again to patients from Latin America countries to ascertain descriptor comprehension. OUTCOME MEASURES: Demographic data, McGill Pain Questionnaire parameters, and visual analog scale and a verbal rating scale scores were obtained from patients with chronic and acute pain. Psychometric properties of the Spanish version of the McGill Pain Questionnaire were established for each country by calculating the ordinal consistency by means of rank-scale correlation (Spearman test), intercategory correlation, and interparameter correlation (Pearson test). Concurrent validity was also calculated by comparing scores from the visual analog scale (Pearson test) and verbal rating scale (Spearman test) with questionnaire parameters (qualitative-to-quantitative comparisons). RESULTS: The Spanish version of the McGill Pain Questionnaire maintained a high internal validity when tested in different countries. Ordinal consistency, intercategory, interparameter, and qualitative-to-quantitative parameter correlations were similar in all countries. Few descriptors were considered to be inappropriate or difficult to understand. CONCLUSIONS: The psychometric properties of the Spanish version of the McGill Pain Questionnaire assessed in different Latin-American countries suggest that the questionnaire may be used to evaluate Spanish-speaking patients. The validity of this test should be extended with reliability studies to further establish its usefulness in the evaluation of pain.

Argentina↗

PubMed2001

[Relationship between prothrombin time international normalized ratio and thrombo test (%)].

OBJECTIVES: The optimal therapeutic range for laboratory evaluation of oral anticoagulant therapy is now defined by the prothrombin time international normalized ratio (PT-INR). However, the thrombo test (TT), an alternative method to measure intensity of anticoagulation, is also currently used throughout Japan. The relationship between PT-INR and TT (%) has yet to be clarified. This study investigated the relationship between PT-INR and TT (%). METHODS: The PT-INR and TT (%) were simultaneously measured of 505 consecutive samples from patients treated with warfarin in our hospital. Fourteen functions were used for regression analyses: a fractional function (Y = a/X + b), a square root function (Y = aX0.5 + b), a natural logarithmic function (Y = a.lnX + b), a power series function (Y = aXb), a quotient function (Y = abX), and polynomial functions [Y = anXn + an - 1Xn - 1 +......+ a1X1 + b, (1 < or = n < or = 9)]. The results were confirmed by the same methods in 383 samples and 296 samples from another two laboratories. RESULTS: The power series function showed the most significant (p < 0.0001) and highest adjusted R2 (0.858) correlation, with a regression formula of TT (%) = e4.48 (PT-INR)-2.09 in our laboratory. Using the same analyses, the power series function also showed the most significant and highest adjusted R2 in samples from the other two laboratories. CONCLUSIONS: This study showed that a power series function is the most appropriate for expressing the relationship between PT-INR and TT (%) among the 14 functions. The function between PT-INR and TT (%) is mainly derived from the relationship between TT (%) and TT (sec). Both internal validity and external validity confirmed the relationship between PT-INR and TT (%).

Aged↗

PubMed2002

[Validation of ESCAP-CD as an instrument of measure for the evaluation of the quality of life in prostatic cancer. Part 2a].

UNLABELLED: In order to make a measure of quality of life related to health (QLRH) useful in the investigation, it must fulfill the psychometric properties (validity, reliability and sensibility). The selection of an instrument is a job for the clinic that must choose the most effective for each proposed objective. We set out the objectives to validate the ESCAP-CDV in a multicentric study in Andalusia. We studied 88 patients who were submitted to the instrument presented to validation and two more tests recognized already: the QLQ-C30 from EORTC gold standard in Europe in the valuation of the neoplastic patients' quality of life and the KARNOFSKY the most clinic utility index in neoplastic patients, used to correlate the items. RESULTS: Questionnaire acceptance analysis: The difficulty of understanding was greater for QLQ C30 items (6.81%) than ESCAP items (1.98%). The lapse of time needed to carry out the test was shorter in the ESCAP test (9.84 min) than in the QLQ C30 (13.13), test. Structural analysis or internal validity analysis: The homogeneity index of the items is high (alfa of Cronbach = 0.93). The dimensionality proposed is not accepted, due to the existence of some modifications pund in the factorial analysis. Finally, the established dimensions: Physical and Emotional Capacity (PEC), 5 items; General Symptoms (GS), 4 items; Pain (P), 3 items; Ligh Functional Capcity (LFC), 4 items; Serious Functional Capacity (SFC), 2 items; Economic State (ES), 3 items; Social and Family State (SFE), 5 items; Capacity Sexual (CSX), 2 items; Isolated Variables (IV), 2 items; and Specific Questionnaire (P), 6 items. The ESCAP is a scale with a normal distribution. Approach or external validity analysis: The ESCAP test is well correlated with the other two scales. Reliability test retest: The interclass correlation coefficient is 0.94 in the ESCAP, not so in the KARNOFSKY that is 0.77. CONCLUSIONS: The ESCAP-CDV is a new instrument of valuation of the QLRH composed of a general questionnaire and other specific test of prostate cancer. It has turned out to be a very homogeneous scale due to its internal consistence (alfa of Cronbach of 0.93), showing that it has a normal distribution, that correlates correctly with the scales compared and it is a valid scale to measure the prostate cancer patients' quality of life. The ESCAP-CDV has shown to be a scale with a high reliability (0.94), setting up as an instrument not only useful for investigation, but to clinical use, as well.

Humans↗

PubMed1992

Assessment of the patient-doctor interaction scale for measuring patient satisfaction.

This study assessed the validity, reliability and usability of the Patient-Doctor Interaction Scale (PDIS) in a university-based family practice center. Health maintenance visits and problem visits were included, and data were collected at the time of the visit and again 1 month later. Three different methods of administration (in-person, telephone, and mail) were used to assess usability. Of 91 patients approached, 1 refused to participate. A total of 64 (70%) patients completed the instrument adequately to permit analysis. PDIS scores correlated with overall assessment of patient satisfaction (P < 0.01), suggesting criterion-based validity. Internal consistency (reliability) of the PDIS was indicated by Cronbach's alpha which were consistently greater than 0.80. Scores and return rates varied by method of administration, with the telephone method performing best. The PDIS appears to fulfill the requirements for a valid, reliable and useful instrument to assess patient satisfaction in family practice settings.

Adult↗

PubMedDate not supplied

Gradient echo MRI for measurement of the pulmonary autograft diameter after transplantation to the aortic root: validation and comparison with ultrasound.

The purpose of this study was to s the value of MRI for measurement of pulmonary autograft diameters after transplantation to the aortic root in adults. Thirty-eight adults underwent this operation. MRI and transesophageal echocardiography (TEE) were performed in 30 and 27 patients, respectively, after a mean follow-up period of 2.8 years. For internal validation of MRI, measurements at the diastolic short and long axes of the sinus level were used. Pulmonary autograft diameters were measured and compared with MRI and TEE at five different levels: the subannular region (1), annulus (2), sinus (3), sinotubular junction (4), and the distal part of the autograft (5). The correlation coefficient (r2) between long- and short-axis measurements for corresponding sinuses was .97. Diameters obtained with MRI were 1 to 3 mm larger than those obtained with TEE (P < .05), except for the annulus at systole (P > .3). Cine gradient echo MRI is an appropriate technique to evaluate pulmonary autograft diameters during follow-up. Concordance with TEE was good, apart from a systematic difference of approximately 2 mm.

Adult↗