Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “External validation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 91 records · Page 5Linked to original sources
PubMed2003

The external validity of controlled clinical trials of psychotherapy for depression and anxiety: a naturalistic study.

Psychotherapy researchers have increasingly called for clinical practice and training to focus on empirically supported therapies tested in randomized controlled clinical trials (RCTs). In this paper, we report data from a naturalistic study of successful treatments in clinical practice that bear on the external validity of ESTs for three disorders. Participants were 242 experienced doctoral-level clinicians who reported on their last successfully treated patient seeking treatment for clinically significant depression, panic, or anxiety without panic. Successful treatments typically take substantially longer than the 8-16 sessions characteristic of efficacy trials for these disorders, even for the briefest treatments (cognitive-behavioural). Of particular relevance for generalizability from RCTs, most patients in clinical practice present with multiple problems other than a single Axis I disorder, which clinicians of all theoretical orientations recognize and treat, and these co-occurring conditions have a substantial impact on treatment length in everyday practice. The data suggest the importance of effectiveness research in bridging research and practice. They also point to the utility of distinguishing two complementary ways in which effectiveness research can be understood and implemented: by starting with efficacy trials and then testing treatments with promising results in the laboratory using broader community samples; or by starting with everyday clinical practice, examining patterns of covariation between specific interventions and outcomes at clinically meaningful follow-up intervals with diverse and ecologically valid samples and using these data to generate prototypes of treatments that can be used to guide the next generation of experimental studies.

Anxiety Disorders↗
PubMed1994

Dysthymia: clinical and external validity.

This paper reviews current evidence in support of dysthymia as a sub-affective disorder that precedes major affective episodes, often by more than a decade. In cases beginning in childhood or adolescence, dysthymia is associated with high familial rates of mood disorders, and a recurrent pattern of superimposed major depression. At least two trait-like markers, sleep electro-encephalographic and thyroid axis abnormalities-similar to those in major affective disorder-have been reported. These data indicate a common pathophysiological substrate for both dysthymia and major depressive illness. All classes of antidepressants-most recently the serotonin re-uptake and the reversible MAO inhibitors-have been shown to be effective. Dysthymia was fairly recently included in the US(DSM) and WHO(ICD) classifications of mental disorders, because it characterises a prevalent clinical presentation of depression in both psychiatric and general medical settings. Patients given this diagnosis, instead of presenting with acute or full-blown episodes, often complain of low-grade chronic affective malaise for as long as they remember, yet without clinically observable signs of depression. As a result, questions have been raised about its validity, but from fundamentally opposite positions: (i) Is dysthymia better conceptualised as a personality (or neurotic) rather than mood disorder? (ii) Can dysthymia be distinguished from major depressive illness? This paper examines these and related questions along both clinical and external validating strategies, and in particular, the more recent accumulated evidence in support of the utility of the concept of dysthymia.

Depressive Disorder↗
PubMed2001

External validity of religiosity scales for a sample of southern students.

When mean scores on the Spiritual or Philosophical Domain of the Coping Resources Inventory for 96 university students of ages 20 to 47 years, were compared with means of the standardization sample, values fell outside the upper limit of the 99% confidence interval, suggesting the scale may not have external validity for a sample of students.

Adult↗
PubMed1976

Testing the internal and external validity of a simplified dental caries index on an adult population.

This analysis of a caries index, proposed in 1966 to WHO as a simplified method of measurement, as tested on a 16- to 45-year-old population who were seeking dental care at the University of Minnesota School of Dentistry revealed several weaknesses associated with the index. An analysis of the external validity of this index, a comparison with subjects' DMFS scores, revealed a correlation coefficient of 0.71. Although the index purports to measure the prevalence and severity of dental caries by dividing the dentition into five zones representing increasing severity of dental caries experience, an analysis of this index's internal validity, i.e. whether these five zones truly represent a rank-order scale of severity, revealed misclassification rates of from 21% for the total population up to 44% for a subgroup. When zones were recombined to reduce the misclassification rates, the descriptive capabilities of the index were greatly reduced as most subjects were then classified in only one or two of the zones.

Adolescent↗
PubMed1999

Internal and external validity of the WHO Well-Being Scale in the elderly general population.

The objectives of this study were (i) to evaluate the validity of the WHO Well-Being Scale in elderly subjects and (ii) to assess the influence of demographic variables on subjective quality of life. A sample of 254 elderly subjects completed the 22-item WHO Well-Being Scale. The scale had an adequate internal and external validity. However, the short 10-item and 5-item versions were equally valid. Low scores indicating decreased well-being were related to the presence of a psychiatric disorder or, independently, to poor living conditions. The Well-Being Scale and their short versions would appear to be useful instruments for identifying subjects with reduced subjective quality of life.

Adult↗
PubMed2001

Classification rules for basic phonological processing disabilities and nonverbal learning disabilities: formulation and external validity.

Rules for the classification of two subtypes of learning disabilities (LD), namely, Basic Phonological Processing Disabilities (BPPD) and Nonverbal Learning Disabilities (NLD), are reported. These rules (refined as a result of application to two separate samples of children with LD) were used to select children from an entirely new sample who could be classified as having "definite" or "probable" BPPD or NLD. As a first step in the external validation of these rules, the patterns of psychosocial functioning exhibited by these two subtypes of LD were determined. As predicted, the vast majority of the BPPD subtype exhibited a pattern most consistent with normal or relatively normal psychosocial adjustment, and no appreciable increase in the incidence of significant psychosocial disturbance with advancing years. Also, as predicted, an increasing incidence of internalized psychosocial dysfunction (a form of significant psychosocial disturbance) was evident in the NLD subtype with advancing years. It is clear that children classified as having BPPD or NLD using these rules exhibit quite different, and predicted, relative patterns of psychosocial functioning. Thus, in this sense, the rules have concurrent validity. Finally, sets of rules/criteria for classification are presented that reflect their actual incidence in the two subtypes of LD generated for use in the validation phase of this investigation. These rules would appear to be useful for clinical purposes. It is also clear that they should be subjected to further validation studies in a broader age range for clinical and research purposes.

Adolescent↗
PubMed2003

External validity in a population-based national prospective study--the Norwegian Women and Cancer Study (NOWAC).

OBJECTIVE: 'The Norwegian Women and Cancer Study' (NOWAC) was created as a national population-based cohort study by taking advantage of the existing population registers in Norway. Thus, the women in the NOWAC study should be representative for the entire female population in the corresponding age-groups. The aim of this paper was to study the external validity of the cohort as a necessary premise for the estimation of population attributable risk. METHODS: Between 1991 and 1997 women were sampled randomly from the national Central person registry in Norway. A total of 179,388 women were invited, of whom 102,443 can be included in the forthcoming follow-up analysis. The response-rates were around 60% in the age-groups 30-34 years till 55-59 years, while 44.7% responded among those aged 65-70 years. Information was collected by postal questionnaires. Follow-up information was based on linkage to national end-point registers with use of the unique national identification number given all Norwegians. RESULTS: Validation of the information on parity and education by linkage to national registers showed only minor differences for these factors between the responders and the total sample of women. A postal survey among non-responders indicated that the most important reasons for not returning the questionnaire were lack of time and concern about privacy. The results showed no differences in life-style factors between the original responders and the non-responders. No significant differences were found between the observed incidence rates for all cancer sites or cancer of the breast compared with national figures for the year 1999. CONCLUSION: The analysis revealed no major source of selection bias that could seriously invalidate the estimation of population attributable risk.

Adult↗
PubMed1993

Chemotherapy induced nausea and emesis in pediatric cancer patients: external validity of child and parent emesis ratings.

Children's and parent's subjective ratings of the frequency and severity of nausea and emesis were assessed among 33 children with acute lymphoblastic leukemia receiving identical chemotherapy. Parents were trained to record the frequency of the child's actual emesis episodes during chemotherapy. Although parent and child ratings of nausea were significantly correlated, children generally rated their nausea and emesis as more frequent and more severe than did their parents. Parent ratings showed inadequate external validity when compared with behavioral observations. Children with greater anxiety and higher subjective ratings subsequently exhibited more frequent episodes of emesis by observation, suggesting that their perceptions of symptoms based on previous chemotherapy experiences may predict emesis during different chemotherapy. In a stepwise multiple regression analysis, antiemetic regimen and the child's anxiety as rated by the parent combined to account for approximately 47% of the variance in number of episodes of emesis. These findings are discussed in the context of factors limiting validity of parent and child reports of children's symptomatology with implications for future epidemiologic and intervention research.

Adolescent↗
PubMed1991

Intracerebral hemorrhage: external validation and extension of a model for prediction of 30-day survival.

We report validation of a previously reported logistic regression model for predicting 30-day survival after supratentorial intracerebral hemorrhage using independent, prospectively collected data. The original model, using initial Glasgow Coma Scale score, hemorrhage size, and pulse pressure, accounted for mortality or survival at 30 days in 92% of patients in the Pilot Stroke Data Bank with a sensitivity of 0.84 and a specificity of 0.96. For external validation, the model was used to predict 30-day status for each patient in the Main Phase Stroke Data Bank for whom complete risk factor information was available. Overall, 90% of patients' outcomes were correctly predicted with a sensitivity of 0.85 and a specificity of 0.92. Two factors not collected in the Pilot Stroke Data Bank, hyperglycemia and intraventricular hemorrhage extension, were assessed to determine if they provided additional predictive information on 30-day mortality. Intraventricular hemorrhage extension contributed significant predictive information in a logistic regression, whereas hyperglycemia did not. The resulting four-factor model with an interaction term (intraventricular hemorrhage extension and Glasgow Coma Scale score) correctly classified the survival status of 94% of patients at 30 days. A more general outcome, death or failure to achieve a "good" Activities of Daily Living Score by one year, was analyzed with respect to the same four factors. The resulting model correctly classified 95% of the patients in the cohort.

Blood Glucose↗
PubMed1980

External validating criteria for psychiatric diagnosis: their application in affective disorders.

Recent advances in biological psychiatry have provided the field with a raison d'être as a unique branch of psychological medicine. Many clinicians are understandably skeptical about the application of such biological techniques in improving the art of clinical diagnosis in psychiatry; most claims for the specificity of biological markers for a given nosological entity have not been replicated. Although much work lies ahead of us, methodological and research findings summarized in this review suggest that certain biological markers are beginning to provide external validating criteria for many psychiatric disorders, especially in the diagnosis of affective illness. Indeed, the rationale and validity of these markers rests on more solid basis than such routine "tests" as proverb interpretation, the Roschach and projective methods in general!

Adult↗
PubMed2003

Theoretically derived CVLT subtypes in HIV-1 infection: internal and external validation.

The present study sought to delineate empirically derived memory subtypes using the California Verbal Learning Test (CVLT; Delis et al., 1987) in a sample of adults with HIV-1 infection (N = 154). Confirmatory factor analysis was used to evaluate eight models of the CVLT structure suggested by Wiegner and Donders (1999). A four-factor model, consisting of Attention Span, Learning Efficiency, Delayed Recall, and Inaccurate Recall appeared to be the best fitting model. Variables with the highest factor loadings from the model were entered in a two-stage cluster analysis. Four reliable CVLT clusters or subtypes were identified: Normal, Atypical, Subsyndromal, and Frontal-striatal. Internal and external validation of subtypes demonstrated that clusters were stable and clinically interpretable. Subtypes were meaningfully related to neuropsychological functioning, and to some extent, depressive symptomatology. Subtypes did not differ significantly with respect to subjective neurocognitive complaints and markers of HIV-1 disease. The present findings highlight the heterogeneity of memory profiles in HIV-1 infection and support a frontal-striatal conceptualization of verbal memory performance. The identification of robust HIV-1 memory subtypes may have important implications for the clinical management of adults infected with HIV-1 infection.

Adult↗
PubMed1993

Do double-blind studies with informed consent yield externally valid results? An empirical test.

Subjective and physiological effects of caffeine were investigated via a 3 x 2 x 3 design that assessed independent and interactive effects of instructions (told caffeine versus told no caffeine versus not told whether beverage contained caffeine), actual beverage content (caffeine versus no caffeine), and time after ingestion (15, 30, and 45 min). Instructions affected alertness at 15 min after ingestion. Caffeine increased alertness at 30 min after ingestion and systolic blood pressure at 30 min and 45 min after ingestion. A highly significant instruction by drug interaction on tension was obtained at all measurement points, indicating an increase in tension only among subjects who knowingly received caffeine. Because people are generally informed of drug content in non-research settings, these data challenge the external validity of typical double-blind studies, in which subjects are informed of the possibility of receiving a placebo as part of the consent procedure.

Adolescent↗
PubMed1993

The factor structure of ADHD items in DSM-III-R: internal consistency and external validation.

Previous research employing factor-analytic procedures to study the underlying dimensions of DSM-III attention deficit disorder with hyperactivity (ADDH) symptoms have consistently supported a two-factor model. Revision of the structure of the ADHD diagnosis in DSM-III-R, as well as inclusion of new items, has raised the question of comparability of the two diagnoses. To explore the significance of these changes, teacher ratings of DSM-III ADDH items and DSM-III-R ADHD items of 85 nonreferred school children were factor-analyzed to determine their underlying factor structures. A similar two-factor solution was obtained for each diagnostic scale. The factors consisted of items believed to reflect inattention and hyperactivity-impulsivity constructs. These factors were further evaluated against results of a cognitive test battery to ascertain whether objective, external validation could be demonstrated. The hyperactivity-impulsivity factor scores were related to continuous performance test measures of response inhibition, while inattention-disorganization factor scores were related to measures of attention and visual search. Implications for assessment and diagnosis of ADHD are discussed.

Attention Deficit Disorder with Hyperactivity↗
PubMed2006

External validity of randomised controlled trials in asthma: to whom do the results of the trials apply?

BACKGROUND: Asthma is a heterogeneous disease with a wide range of clinical phenotypes, not all of which may be encompassed in the subjects included in randomised controlled trials (RCTs). This makes it difficult for clinicians to know to what extent the evidence derived from RCTs applies to a given patient. AIM: To calculate the proportion of individuals with asthma who would have been eligible for the major asthma RCTs from the data of a random community survey of respiratory health. METHODS: A postal survey was sent to 3500 randomly selected individuals aged 25-75 years. Respondents were invited to complete a detailed respiratory questionnaire and pulmonary function testing. Participants with current asthma were assessed against the eligibility criteria of the 17 major asthma RCTs cited in the Global Initiative for Asthma (GINA) guidelines. FINDINGS: A total of 749 participants completed the full survey, of whom 179 had current asthma. A median 4% of participants with current asthma (range 0-36%) met the eligibility criteria for the included RCTs. A median 6% (range 0-43%) of participants with current asthma on treatment met the eligibility criteria. INTERPRETATION: This study shows that the major asthma RCTs on which the GINA guidelines are based may have limited external validity as they have been performed on highly selected patient populations. Most of the participants with current asthma on treatment in the community would not have been eligible for these RCTs.

Adult↗
PubMed2006

External validity of randomized controlled trials in COPD.

BACKGROUND: COPD is a heterogeneous disease comprising a wide range of clinical phenotypes, depending on the degree to which emphysema, chronic bronchitis, reversible bronchospasm and small airways inflammation are present. Not all of these phenotypes may be represented among the subjects included in randomized controlled drug trials (RCTs) in COPD, making it difficult for doctors to know to what extent RCT evidence applies to individual patients. From a respiratory health survey of adults randomly selected from the community, we have estimated the proportion of subjects with COPD who would have been eligible for inclusion in major COPD RCTs. METHODS: A postal survey was sent to 3500 randomly selected individuals aged 25-75 years. Respondents were invited to complete a detailed respiratory questionnaire and pulmonary function tests. Subjects with COPD defined by post-bronchodilator spirometry were assessed against the eligibility criteria of 18 major RCTs cited in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines. FINDINGS: Of 749 subjects completing the full survey, 117 had COPD. Of these, a median of 5% (range 0-20%) of subjects met inclusion criteria for the major RCTs. Of 55 subjects with COPD receiving treatment, 0-9% (median 5%) met inclusion criteria for the major RCTs. INTERPRETATION: The major COPD RCTs on which the GOLD treatment guidelines are based may have limited external validity. Over 90% of the COPD subjects in the community who were taking medication, did so on the basis of RCTs for which they would not have been eligible.

Adult↗
PubMed2005

External validation, extension and recalibration of Braunwald's simple risk index in a community-based cohort of patients with both STEMI and NSTEMI.

BACKGROUND: Using the simple risk index (SRI) that is based on age, heart rate and systolic blood pressure, we sought to evaluate the ability to predict outcome in AMI patients in a community-based population. METHODS AND RESULTS: We identified and evaluated 3684 consecutive patients with an admission diagnosis of possible AMI, who attended between 1st September and 30th November 1995. Two thousand one hundred fifty three patients had confirmed evidence of WHO definition AMI, of whom 1656 survived to hospital discharge. We evaluated the ability of the SRI to predict mortality over 30 days using the score generated by the equation (heart ratex[age/10]2)/systolic blood pressure. The SRI was a strong (c-statistic = 0.77 CI 0.74-0.79) predictor of 30-day mortality in both STEMI and all consecutive cases of WHO definition AMI. However, the model showed poor calibration when used on a community-based population with 30-day mortality being underestimated across all risk quintiles. Consequently we sought to recalibrate the quantitative aspects of the model for the total AMI population in the following way (Risk Index; 30-day mortality) (< or = 29.2; 9.2%), (29.3-37.8; 23.9%), (37.9-47.3; 34.6%), (47.4-61.5; 40.3%), (> or = 61.6; 65.5%). CONCLUSION: We have externally validated the SRI in an unselected cohort of consecutive WHO definition AMI patients. However, the original model consistently underestimated the likelihood of death at 30 days regardless of the calculated risk score. We have therefore suggested corrections to the risk estimates, to allow its application in an unselected community cohort.

Age Factors↗
PubMed2005

Internal and external validity of attention-deficit hyperactivity disorder in a population-based sample of adults.

BACKGROUND: Follow-up studies of childhood ADHD have shown persistence of the disorder into adulthood, but no epidemiological data are yet available. METHOD: ADHD DSM-IV symptoms were obtained by self-report in an adult population-based sample of 1813 adults (aged 18-75 years), that was drawn from an automated general practitioner system used in Nijmegen, The Netherlands. The structure of ADHD symptoms was analysed by means of confirmatory factor analyses. Other data used in this report are the General Health Questionnaire (GHQ-28), information about the presence of three core symptoms of ADHD in childhood, and about current psychosocial impairment. RESULTS: The three-factor model that allowed for cross-loadings provided the best fit in the entire sample. This result was replicated across gender and age subsamples. Inattentive and hyperactivity symptom scores were significantly associated with measures of impairment, even after controlling for the GHQ-28. Subjects with four or more inattentive or hyperactive-impulsive symptoms were significantly more impaired than subjects with two, one and no symptoms. The prevalence of ADHD in adults was 1.0% (95% CI 0.6-1.6) and 2.5% (1.9-3.4) using a cutoff of six and four current symptoms respectively, and requiring the presence of all three core symptoms in childhood. CONCLUSIONS: These results support the internal and external validity of ADHD in adults between 18 and 75 years. ADHD is not merely a child psychiatric disorder that persists into young adulthood, but an important and unique manifestation of psychopathology across the lifespan.

Adolescent↗
PubMed2006

External validation of the Mayo Clinic Stage, Size, Grade and Necrosis (SSIGN) score to predict cancer specific survival using a European series of conventional renal cell carcinoma.

PURPOSE: We validated the Mayo Clinic SSIGN score in an independent European sample of patients who were surgically treated for conventional RCC. MATERIALS AND METHODS: In our kidney cancer database we identified 388 patients who were treated with radical or partial nephrectomy for conventional RCC between 1986 and 2000. Associations of the pathological features studied with death from RCC were evaluated using the log rank test and Cox proportional hazards regression model. The predictive ability of competing models was evaluated using the c index. RESULTS: Median followup in the 290 patients who were alive at last followup was 5 years (range 5 months to 17 years). The estimated cancer specific survival rate 5 years following surgery was 81.3%. All features that comprise the SSIGN score except tumor size were significantly associated with death from RCC in a multivariate setting, resulting in a c index of 0.90. The median SSIGN score in the 388 patients studied was 3 (range 0 to 15). The c index in a model containing the clear cell SSIGN score was 0.88. Five-year cancer specific survival rates in patients with a score of 0 to 2, 3 to 4, 5 to 6, 7 to 9 and 10 or more were 100.0%, 90.5%, 63.6%, 46.8% and 0%, respectively. CONCLUSIONS: We provide the first external validation of the Mayo Clinic SSIGN score for conventional RCC. This simple algorithm resulted in a high degree of prognostic accuracy.

Adult↗