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PubMed2005

Reducing ultraviolet radiation exposure to prevent skin cancer methodology and measurement.

Skin cancer is the most common type of cancer, and is also one of the most preventable. This paper builds on an evidence review of skin cancer prevention interventions that was conducted for the Guide to Community Preventive Services (n=85 studies), and summarizes the state of knowledge about research methodology and measurement in studies of the effectiveness of interventions to reduce ultraviolet radiation (UVR) exposure. As this field advances, researchers should strive to minimize threats to validity in their study designs, as well as to consider the balance between internal and external validity. There is a need for more longer-duration interventions, and follow-up periods that make possible conclusions about the potential of these interventions to affect intermediate markers of skin cancer or at least sustained behavior change. Also, more work is needed to minimize attrition and characterize nonresponders and study dropouts. Verbal report measures of behavior are the most widely used measures of solar protection behavior. Given their limitations, investigators should routinely collect data about reliability and validity of those measures. They should also increase efforts to complement verbal data with objective measures including observations, skin reflectance, personal dosimetry, skin swabbing, and inspection of moles. Measures of environments and policies should incorporate observations, documentation, and direct measures of ambient UVR and shade. This article places the data derived from the evidence review in the context of needs and recommendations for future research in skin cancer prevention.

Environmental Exposure↗
PubMed2005

HPLC and chemometric assisted spectrophotometric methods for simultaneous determination of diprophylline, phenobarbitone and papaverine hydrochloride.

Three methods are developed for the simultaneous determination of diprophylline (DP), phenobarbitone (PH) and papaverine hydrochloride (PP). The chromatographic method depends on a high performance liquid chromatographic (HPLC) separation on a reversed-phase C18 column with a mobile phase consisting of 0.02 M potassium dihydrogen phosphate, pH 3.5--acetonitrile (55:45 v/v). Quantitation was achieved with UV detection at 210 nm based on peak area. The other two chemometric methods applied were principal component regression (PCR) and partial least squares (PLS-1). These approaches were successfully applied to quantify the three drugs in the mixture using the information included in the UV absorption spectra of appropriate solutions in the range 215-245 nm with the intervals Delta lambda = 0.2 nm. The calibration PCR and PLS-1 models were evaluated by internal validation (prediction of compounds in its own designed training set of calibration), by cross-validation (obtaining statistical parameters that show the efficiency for a calibration fit model) and by external validation over laboratory-prepared mixtures and pharmaceutical preparations. The PCR and PLS-1 methods require neither any separation step, nor any priori graphical treatment of the overlapping spectra of the three drugs in a mixture. The results of PCR and PLS-1 methods were compared with HPLC method obtained in pharmaceutical formulation and a good agreement was found.

Bronchodilator Agents↗
PubMed2006

Application and validation of chemometrics-assisted spectrophotometry and liquid chromatography for the simultaneous determination of six-component pharmaceuticals.

Three methods are developed for the simultaneous determination of theophylline anhydrous (TH), guaiphenesin (GP), diphenhydramine hydrochloride (DP), methylparaben (MP), propylparaben (PP) and sodium benzoate (BZ) in pharmaceutical syrup. The chromatographic method depends on a high performance liquid chromatographic separation on a reversed-phase C(18) column at ambient temperature with mobile phase consisting of 25 mM KH2PO4, pH 3.2-acetonitrile (60:40, v/v). Quantitation was achieved with UV detection at 222 nm based on peak area. The other two chemometric methods applied were partial least squares (PLS-1) and principal component regression (PCR). These approaches were successfully applied to quantify the six components in the studied mixture using information included in the UV absorption spectra of appropriate solutions in the wavelength range of 220-270 nm with Deltalambda=0.4 nm. The calibration PLS-1 and PCR models were evaluated by internal validation (prediction of compounds in its own designed training set of calibration), by cross-validation (obtaining statistical parameters that show the efficiency for a calibration fit model) and by external validation over synthetic and pharmaceutical preparation. The results of PLS-1 and PCR methods were compared with the HPLC method and a good agreement was found.

Antitussive Agents↗
PubMed1998

The Collaborative Ocular Melanoma Study (COMS) randomized trial of pre-enucleation radiation of large choroidal melanoma I: characteristics of patients enrolled and not enrolled. COMS report no. 9.

PURPOSE: To describe the baseline characteristics and status of patients enrolled in the Collaborative Ocular Melanoma Study (COMS) randomized clinical trial of pre-enucleation radiation of large choroidal melanoma conducted in the United States and Canada, and to compare characteristics of patients enrolled with those of patients with tumors of eligible size who were not enrolled in order to assess the generalizability of findings from the clinical trial. METHODS: For all patients evaluated for the clinical trial at COMS centers from November 1986 through December 15, 1994, selected data were transmitted to the COMS Coordinating Center. For patients who enrolled in the clinical trial, ophthalmic and medical history, examination findings, and visual acuity measurements were recorded prior to enrollment. Standardized A-scan and contact B-scan echographic examinations were performed prior to enrollment, and photoechograms were submitted for central review for consistency with the diagnosis, independent measurement of the apical height of the tumor, and description of tumor configuration and internal reflectivity for each patient enrolled. Until January 1992, wide-angle fundus photographs and fluorescein angiograms taken prior to enrollment also were submitted for central review to confirm consistency with the diagnosis. All data were integrated and analyzed at the COMS Coordinating Center. RESULTS: Of 6,078 patients with choroidal melanoma evaluated in COMS centers, 1,860 had tumors of eligible size; of these, 1,302 (70%) were eligible for the clinical trial, and 1,003 (77% of eligible patients) enrolled. The two principal reasons for ineligibility were other primary cancer and predominantly ciliary body melanoma. Ineligible patients were older than eligible patients, had larger choroidal melanoma, and had poorer visual acuity at the time of evaluation for the COMS (P < .01, Wilcoxon rank sum tests). Patients eligible for the clinical trial had a mean age of 60 years; 56% were male; almost all (97%) were non-Hispanic whites. Among eligible patients, mean tumor apical height was 9.5 mm and mean longest basal diameter was 17.2 mm. Eligible patients who enrolled in the trial were similar to eligible patients who did not enroll with respect to most factors considered. Those who enrolled had longer tumor basal diameter and better visual acuity in the fellow eye, more often had their primary residence in Canada, and less often had education beyond high school than did eligible patients who did not enroll (P < .05, Wilcoxon rank sum tests and chi2 tests, respectively). CONCLUSIONS: The COMS clinical trial of pre-enucleation radiation was designed to yield internally valid treatment comparisons through random treatment assignment at time of enrollment. Findings also have high external validity because a majority (54%) of all patients with tumors of eligible size, and a large majority (77%) of all eligible patients, were enrolled. Furthermore, patient characteristics are similar to those of patients included in other evaluations of this method of treating large choroidal melanoma. Thus, findings from this clinical trial apply to all patients who have large choroidal melanoma and satisfy COMS eligibility criteria.

Adult↗
PubMed2003

Preoperative prediction of severe postoperative pain.

We developed and validated a prediction rule for the occurrence of early postoperative severe pain in surgical inpatients, using predictors that can be easily documented in a preoperative setting. A cohort of surgical inpatients (n=1416) undergoing various procedures except cardiac surgery and intracranial neurosurgery in a University Hospital were studied. Preoperatively the following predictors were collected: age, gender, type of scheduled surgery, expected incision size, blood pressure, heart rate, Quetelet index, the presence and severity of preoperative pain, health-related quality of life the (SF-36), Spielberger's State-Trait Anxiety Inventory (STAI) and the Amsterdam Preoperative Anxiety and Information Scale (APAIS). The outcome was the presence of severe postoperative pain (defined as Numeric Rating Scale > or =8) within the first hour postoperatively. Multivariate logistic regression in combination with bootstrapping techniques (as a method for internal validation) was used to derive a stable prediction model. Independent predictors of severe postoperative pain were younger age, female gender, level of preoperative pain, incision size and type of surgery. The area under the receiver operator characteristic (ROC) curve was 0.71 (95% CI: 0.68-0.74). Adding APAIS scores (measures of preoperative anxiety and need for information), but not STAI, provided a slightly better model (ROC area 0.73). The reliability of this extended model was good (Hosmer and Lemeshow test p-value 0.78). We have demonstrated that severe postoperative pain early after awakening from general anesthesia can be predicted with a scoring rule, using a small set of variables that can be easily obtained from all patients at the preoperative visit. Before this internally validated preoperative prediction rule can be applied in clinical practice to support anticipatory pain management, external validation in other clinical settings is necessary.

Adolescent↗
PubMed2004

Development and initial validation of a new preference-based disease-specific health-related quality of life instrument for erectile function.

UNLABELLED: Health-related quality of life instruments may be generic or specific. In general, only generic instruments use preference-based scoring. We report on a novel approach to combine in one instrument the strengths of the specific approach, greater disease relevance and responsiveness, with those of preference-based scoring, generalizability through utilities. OBJECTIVES: The primary objective was to develop a self-administered, preference-based instrument capable of measuring utilities in the disease-specific context of erectile dysfunction (ED). METHODS: Content derivation/validation began with a literature review. Eight attributes (domains) were selected to provide clinical experts structure for focus group discussion. Four levels describing a continuum of dysfunction-function were defined for each domain. Each domain, including functional levels, was reviewed and modified until consensus was achieved regarding content. This content was then integrated into a preference based scoring instrument using two visual analogue scales (VAS) with which patients rated three 'marker' health states (representing mild, moderate and severe ED), their self-state and a previously validated external marker state. The instrument was pilot tested, and implemented in a clinical trial. Initial validation analyses have been performed. RESULTS: A self-administered, preference-based, VAS instrument was developed for use in the ED population, and the instrument was feasible to complete, was reliable beyond the threshold of acceptability established a priori and demonstrated good validity. Evidence of these properties accumulates over time and this study begins that process with this instrument. Responsiveness is being assessed in the context of a clinical trial.

Adult↗
PubMed2002

Lower reference limit for maximal oxygen uptake in men and women.

Maximal oxygen uptake (VO2max) is an important measure of exercise tolerance and low values may have clinical significance. Our purpose was to develop the necessary statistics--prediction equations and standard errors of estimate (SEE)--so that the lower reference limit for VO2max can be predicted for men and women. The subjects were healthy, non-smoking, sedentary men (n = 115) and women (n = 115) aged 20-70 years who performed 15 W min-1 cycle ergometer exercise tests. Three equations were developed for each gender using multiple linear regression with the non-exercise predictor variables of age and height, age and mass, and age and fat-free mass (FFM). The assumptions of regression analysis were examined and the predicted residual sum of squares (PRESS) method was used to cross-validate each equation. Healthy and diseased individual subject data from the literature were used to externally validate our lower reference limit statistics. The equations developed meet the assumptions of regression analysis and have an accuracy similar to the non-exercise prediction equations in the literature with R2 values of approximately 0.581. The PRESS method revealed that the equations are generalizable, i.e. may be used in future studies without a significant loss of accuracy. The lower reference limit predictions for the healthy and diseased individual subject data from the literature produced few miscategorizations unless the subjects were obese and mass was used as a predictor variable. In conclusion, the equations and SEE generated in this study can be used to predict an accurate and valid VO2max lower reference limit for a given subject.

Adult↗
PubMed2004

Proving the value of simulation in laparoscopic surgery.

OBJECTIVE: To assess the McGill Inanimate System for Training and Evaluation of Laparoscopic Skills (MISTELS) physical laparoscopic simulator for construct and predictive validity and for its educational utility. SUMMARY BACKGROUND DATA: MISTELS is the physical simulator incorporated by the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) in their Fundamentals of Laparoscopic Surgery (FLS) program. MISTELS' metrics have been shown to have high interrater and test-retest reliability and to correlate with skill in animal surgery. METHODS: Over 200 surgeons and trainees from 5 countries were assessed using MISTELS in a series of experiments to assess the validity of the system and to evaluate whether practicing MISTELS basic skills (transferring) would result in skill acquisition transferable to complex laparoscopic tasks (suturing). RESULTS: Face validity was confirmed through questioning 44 experienced laparoscopic surgeons using global rating scales. MISTELS scores increased progressively with increasing laparoscopic experience (n = 215, P < 0.0001), and residents followed over time improved their scores (n = 24, P < 0.0001), evidence of construct validity. Results in the host institution did not differ from 5 beta sites (n = 215, external validity). MISTELS scores correlated with a highly reliable validated intraoperative rating of technical skill during laparoscopic cholecystectomy (n = 19, r = 0.81, P < 0.0004; concurrent validity). Novice laparoscopists were randomized to practice/no practice of the transfer drill for 4 weeks. Improvement in intracorporeal suturing skill was significantly related to practice but not to baseline ability, career goals, or gender (P < 0.001). CONCLUSION: MISTELS is a practical and inexpensive inanimate system developed to teach and measure technical skills in laparoscopy. This system is reliable, valid, and a useful educational tool.

Clinical Competence↗
PubMed1995

Psychiatric morbidity in primary public health care: a Nordic multicentre investigation. Part I: method and prevalence of psychiatric morbidity.

The prevalence of mental illness in five different Scandinavian primary care populations was investigated in this study. Patients consecutively consulting their general practitioner a particular week-day were included in the study. Initially the SCL-25 was applied and next the high scores and a sample of the low scores were interviewed by the PSE. In the analysis the screening procedure was first validated. The internal validity of the SCL was tested by means of Rasch latent structure analysis and the external validity tested by ROC/QROC analysis. Based on this, a short 8-item version of the SCL was developed. The prevalence of mental illness in all centres was 0.26 with a minimum of 0.14 in Nacka and a maximum of 0.34 in Turku.

Adolescent↗
PubMed1995

Comparison of different indices of dietary control in phenylketonuria.

Ten different indices of dietary control (IDCs) applied frequently to investigate compliance of phenylketonuric patients were calculated for a set of blood phenylalanine levels for 98 patients in the German Collaborative Study of Children Treated for Phenylketonuria during their first 9 years of life. The results were compared for similarities and differences. Cluster analysis of longitudinal phenylalanine data was introduced to analyse phenylalanine blood levels independent of a priori defined criteria of classification. Three groups of good, intermediate and poor long-term dietary control were identified. Internal validation of the IDCs was corroborated by the high inter-correlations of the indices. External validity was determined by the inter-relations of the WISC-R IQ and the IDCs. The different algorithms of IDCs suggest different clinical conclusions. To facilitate comparisons of results of future research, IDCs should be standardized.

Child↗
PubMed1996

Symptom dimensions of schizophrenia: a selective integration of neurophysiological and neuropsychological correlates.

Schizophrenia is a heterogeneous and multidimensional disorder. The different syndromes or dimensions of this disorder represent distinct pathophysiological processes. Evidence is growing that each of the composite syndromes or dimensions of this disorder is associated with specific validators. This article reviewed neurophysiological and neuropsychological studies in schizophrenia in order to determine the external validators of its syndromes. The review reveals compelling findings in some instances and contradictory findings in other instances.

Brain↗
PubMed1999

The validity of DSM-IV alcohol abuse: drunk drivers versus all others.

OBJECTIVE: Prior research in a community sample indicated that almost half the individuals receiving a diagnosis of DSM-IV alcohol abuse did so on the basis of only one symptom, driving after drinking too much. While this is certainly unwise behavior, it may not be a psychiatric disorder. Therefore, we investigated the differential validity of this subgroup of abuse cases by testing the association of a set of external validating criterion variables with three groups: those who met criteria for abuse just for drinking-driving, those who met criteria by other means and those with no alcohol diagnosis. Present status of past cases of abuse was also investigated. METHOD: Subjects were 22,204 U.S. household residents (a subset of a national probability sample) interviewed in 1992 with the Alcohol Use Disorders and Associated Disabilities Interview Schedule. The generalized logit model was the principal means of analysis. RESULTS: Subjects who met criteria for DSM-IV alcohol abuse just for drinking-driving differed from subjects with no diagnosis on about half the variables tested, while those who met criteria for abuse in other ways differed from subjects with no diagnosis on all variables tested. The two abuse groups differed from each other on some but not all variables. Past cases of abuse for drinking-driving and past cases of other abuse were equally likely to have remitted in the last 12 months, and slightly less likely to meet criteria for current dependence. CONCLUSIONS: Further conceptual and empirical work is needed to resolve the difficulties with the DSM-IV alcohol abuse category.

Adolescent↗
PubMed2002

A new classification tool for clinical differentiation between haemorrhagic and ischaemic stroke.

PURPOSE: To develop a simple and reliable diagnostic tool for differentiation of cerebral infarction (CIF) from intracerebral haemorrhage (ICH) in order to aid clinicians to decide about starting antiplatelet therapy in settings where rapid access to computed tomography (CT) is lacking. METHODS: Thirty variables regarding each patient admitted with acute stroke were recorded and considered in a logistic regression analysis using ICH as end-point (internal study). CT was used as the golden standard. The score derived was validated with data from the next consecutive stroke patients and was compared with the three preexisting scores (external validation study). RESULTS: Amongst 235 patients (119 males, mean age 70.6 +/- 11.2 years) of the internal study, 43 (18.3%) had ICH. Four independent correlates of ICH were identified and used for the derivation of the following integer-based scoring system: number of points=6 * (neurological deterioration within 3 h from admission) + 4 * (vomiting) + 4 * (WBC > 12 000) + 3 * (decreased level of consciousness). In the external study [168 patients, 85 males, mean age 70.2 +/- 10.8 years, 31 (18.5%) with ICH], when the cut-offs < or =3 points for CIF and > or =11 points for ICH were used, sensitivity, specificity, and positive and negative predictive values of the score for detection of stroke type were 97, 99, 97 and 99%, respectively; exceeding noticeably the three previously proposed systems. CONCLUSIONS: The proposed model provides an easy to use tool for sufficiently accurate differentiation between haemorrhagic and nonhaemorrhagic stroke on the basis of information available to all physicians early after admission.

Acute Disease↗
PubMed2003

Complicated left-sided native valve endocarditis in adults: risk classification for mortality.

CONTEXT: Complicated left-sided native valve endocarditis causes significant morbidity and mortality in adults. Lack of valid data regarding estimation of prognosis makes management of this condition difficult. OBJECTIVE: To derive and externally validate a prognostic classification system for adults with complicated left-sided native valve endocarditis. DESIGN, SETTING, AND PATIENTS: Retrospective observational cohort study conducted from January 1990 to January 2000 at 7 Connecticut hospitals among 513 patients older than 16 years who experienced complicated left-sided native valve endocarditis and who were divided into derivation (n = 259) and validation (n = 254) cohorts. MAIN OUTCOME MEASURE: All-cause mortality at 6 months after baseline. RESULTS: In the derivation and validation cohorts, the 6-month mortality rates were 25% and 26%, respectively. Five baseline features were independently associated with 6-month mortality (comorbidity [P =.03], abnormal mental status [P =.02], moderate to severe congestive heart failure [P =.01], bacterial etiology other than viridans streptococci [P<.001 except Staphylococcus aureus, P =.004], and medical therapy without valve surgery [P =.002]) and were used to create a prognostic classification system. In the derivation cohort, patients were classified into 4 groups with increasing risk for 6-month mortality: 5%, 15%, 31%, and 59% (P<.001). In the validation cohort, a similar risk among the 4 groups was observed: 7%, 19%, 32%, and 69% (P<.001). CONCLUSIONS: Adults with complicated left-sided native valve endocarditis can be accurately risk stratified using baseline features into 4 groups of prognostic severity. This prognostic classification system might be useful for facilitating management decisions.

Adult↗
PubMed1992

The validity of autistic spectrum disorders: a literature review.

The objective of this literature review is to assess the validity of autistic spectrum disorders (ASD). Twenty papers were identified that adequately investigated the internal or external validity of various subtypes of ASD. At least three groups can be distinguished from autism on clinical grounds; an Asperger syndrome subtype, and two atypical subtypes characterized by low IQ and high IQ. However, the evidence that these clinical distinctions carry inferences with respect to etiology, clinical course, and treatment is only suggestive. Nevertheless, the specification of several ASD subtypes might promote further research and resolve many of the nosologic issues with respect to the classification of pervasive developmental disorders (PDDs).

Autistic Disorder↗
PubMed2000

Predictive validity of symptoms and signs in the neck and shoulders.

A standardized examination protocol was developed for the assessment of neck and shoulder disorders in primary health care. We investigated to what extent the symptoms and signs can predict sick leave due to neck and shoulder disorders. Our study involved 474 patients seeking medical advice from an occupational health service. Most of the 20 symptoms and 15 signs of the protocol were associated with the number of sick leave days within the 60-day postexamination period, but only three symptoms (short duration, high pain intensity, and continuous pain) and two signs (pain in the upper limb during rotation of head and pain in the shoulder during abduction of arm) retained their significance in a multivariate model. No unambiguous subset of protocol items can be suggested for general use. The predictive validity should be tested in other populations and settings before a conclusion is drawn about the external validity of the results.

Adult↗
PubMed2006

Performance of multicomponent self-organizing regression (MCSOR) in QSAR, QSPR, and multivariate calibration: comparison with partial least-squares (PLS) and validation with large external data sets.

A novel method for underdetermined regression problems, multicomponent self-organizing regression (MCSOR), has been recently introduced. Here, its performance is compared with partial least-squares (PLS), which is perhaps the most widely adopted multivariate method in chemometrics. A potpourri of models is presented, and MCSOR appears to provide highly predictive models that are comparable with or better than the corresponding PLS models in large internal (leave-one-out, LOO) and pseudo-external (leave-many-out, LMO) validation tests. The "blind" external predictive ability of MCSOR and PLS is demonstrated employing large melting point, factor Xa, log P and log S data sets. In a nutshell, MCSOR is fast, conceptually simple (employing multiple linear regression, MLR, as a statistical tool), and applicable to all kinds of multivariate problems with single Y-variable.

Algorithms↗