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PubMed1999

The WOMB (Women's views of birth) antenatal satisfaction questionnaire: development, dimensions, internal reliability, and validity.

BACKGROUND: Antenatal services continue to change, stimulated by the Changing Childbirth report. Women's views should be an important component of assessing the quality of such services. To date, no published quantitative multidimensional assessment instrument has been available to measure their satisfaction with care. AIM: To develop a valid, reliable, multidimensional questionnaire to assess quality of antenatal care. METHOD: A multidimensional satisfaction questionnaire was developed using psychometric methods. Following fieldwork to pilot a questionnaire, three successive versions of it were given by midwives to pregnant women in their final trimester in nine trusts in the old South Western region of England. Their replies were analysed by principal components analysis (PCA) with varimax rotation; internal reliability was assessed by Cronbach's alpha. Face, content, and construct validity were all assessed during development. RESULTS: Out of 196 women, 134 (68.4%) returned the pilot questionnaires. One hundred and seventy-two (57.3%) out of 300 women returned version 1 of the WOMB (WOMen's views of Birth) antenatal satisfaction questionnaire proper, 283 (56.6%) out of 500 returned version 2, and 328 (65.6%) out of 500 returned the final development version. This final version consisted of 11 dimensions in addition to a general satisfaction one. These were [Cronbach's alpha]: five related to antenatal clinic characteristics (travelling to clinic [0.75], waiting at clinic [0.90], clinic environment [0.69], timing of appointment [0.78], car parking [0.85]), three 'professional' characteristics (professional competence [0.80], knowing carers [0.79], information provided [0.81]), antenatal classes [0.76], social support from other pregnant women [0.83], checking for the baby's heart beat [0.63]. There were significant moderate correlations (range = 0.24 to 0.77) between individual dimensions and the general satisfaction dimension. Women's dimension scores were significantly related to age, parity, social class, and best educational achievement. CONCLUSION: This multidimensional satisfaction instrument has good face, content, and construct validity, and excellent internal reliability. It could be used to generally assess antenatal services or to screen them to detect areas where further in-depth qualitative enquiry is merited. Its sensitivity to change over time, external reliability, and transferability to non-Caucasian groups needs to be assessed.

Adult↗

PubMed1987

Do smoking prevention programs really work? Attrition and the internal and external validity of an evaluation of a refusal skills training program.

This study investigated the effects of a smoking prevention program that emphasized refusal skills training on 1730 adolescents in three high schools and six middle schools. Classes within these schools were randomly assigned to treatment or no-treatment conditions to avoid confounding schools with treatment condition. The effects of attrition on the internal and external validity of the study were examined. Although the results indicated an apparent effect of the program at the 1-year follow-up in deterring continued smoking among those who were smoking at pretest, this result may have been due to a higher rate of attrition among high-rate smokers in the treatment condition than in the control condition. Attrition also affected external validity. Across both conditions, subjects who were smoking at pretest and who were at risk to smoke were more likely to be missing at follow-up. The program did have an effect on the refusal skills of participants and the validity of this effect was not jeopardized by differential attrition.

Adolescent↗

PubMed1999

Science, ethnicity, and bias: where have we gone wrong?

The quality, quantity, and funding of ethnic minority research have been inadequate. One factor that has contributed to this inadequacy is the practice of scientific psychology. Although principles of psychological science involve internal and external validity, in practice psychology emphasizes internal validity in research studies. Because many psychological principles and measures have not been cross-validated with different populations, those conducting ethnic minority research often have a more difficult time demonstrating rigorous internal validity. Thus, psychology's overemphasis of internal as opposed to external validity has differentially hindered the development of ethnic minority research. To develop stronger research knowledge on ethnic minority groups, it is important that (a) all research studies address external validity issues and explicitly specify the populations to which the findings are applicable; (b) different research approaches, including the use of qualitative and ethnographic methods, be appreciated; and (c) the psychological meaning of ethnicity or race be examined in ethnic comparisons.

Bias↗

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↗

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↗

PubMed2006

Validation of an internal method for the diagnosis of infections with Chlamydophila abortus and Coxiella burnetii by real-time multiplex PCR.

Chlamydophila abortus and Coxiella burnetii are one of the major pathogens implicated in abortion in cattle. Their characteristic of obligate intracellular bacteria, and of zoonotic agents, makes their culture difficult in diagnostic laboratories, and the traditional tools of diagnosis (detection of sera antibodies by ELISA, Stamp's coloration) encounter specificity, sensitivity and interpretability limits. Individual PCR have recently been developed. Nevertheless, their income/cost is a limiting factor for breeders. As the symptoms are not specific, the request for analysis often concerns the two valences. Consequently, the development and the validation of an internal multiplex PCR appears to be a suitable solution.

Abortion, Veterinary↗

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↗

PubMedDate not supplied

Adoption and validation of the international normalized ratio for monitoring oral anticoagulant therapy: the situation in 1989.

The INR/ISI system has been validated in multicenter trials. The system provides a reliable scale for the intensity of oral anticoagulation. It has been recognized that the ISI is slightly dependent on the instrument used for prothrombin time determination. External quality assessment (EQA) of the INR in national programs should be stimulated. EQA results suggest that the precision of the INR can be improved. Many physicians prescribing coumarin congeners are not familiar with the INR system. Improvement of the situation can only be achieved by continuous education.

Administration, Oral↗

PubMed1999

The Nottingham Health Profile: score distribution, internal consistency and validity in asthma and COPD patients.

This cross-sectional study among patients with asthma or Chronic Obstructive Pulmonary Disease (COPD) in general practice examined the psychometric properties of the Nottingham Health Profile (NHP). From 380 asthma patients and 170 COPD patients, data were obtained on the NHP, subjective measurements (i.e. sleep disturbances, problems in performing household activities, dyspnoea) and more objective measurements (peak expiratory flow rate, consultation rate, comorbidity). These data were used to compute score distributions, internal consistency (Cronbach's alpha-coefficient) and construct validity. Score distributions were very skewed, with more than 50% of the patients achieving the best score. The internal consistency was moderate in the asthma group (mean alpha = 0.68) and acceptable in the COPD group (mean alpha = 0.74). Acceptable construct validity was found in both groups. Correlations between the NHP and the subjective measurements were, in general, statistically significant and higher than between the NHP and the more objective measurements. In conclusion, acceptable internal consistency and construct validity implies that the NHP can be used in cross-sectional studies concerning asthma and COPD patients in general practice, and in studies comparing these patients with other patient populations. Further research on the responsiveness of the NHP is needed to justify its use in longitudinal studies.

Adult↗

PubMed2005

[Internal consistency and validity of the Spanish version of the St. George's respiratory questionnaire for use in patients with clinically stable bronchiectasis].

OBJECTIVE: To analyze the reliability and validity of the St. George's Respiratory Questionnaire (SGRQ) for use in patients with clinically stable bronchiectasis. MATERIAL AND METHODS: The SGRQ (50 items on 3 scales--symptoms, activity, and impact) was administered to 102 patients (mean [SD] age, 69.5 [8.7] years; 63% men) with clinically stable bronchiectasis. Disease severity was classified according parameters such as airflow obstruction (forced expiratory volume in 1 second), colonization by Pseudomonas aeruginosa, extent of bronchiectasis, symptoms, daily quantity of sputum, and number of exacerbations. Internal consistency (Cronbach's alpha and correlation between items and between item and scale), concurrent validity (correlation between items and clinical variables), predictive validity (correlation between items and severity), and construct validity (factorial analysis of main components) were assessed. RESULTS: The internal consistency of the SGRQ was excellent (Cronbach's alpha between 0.81 and 0.87 for the different scales, and 0.90 for the overall score). Concurrent validity was high, as correlations between items and clinical variables were significant and followed the expected distribution. The SGRQ differentiated between degrees of disease severity, regardless of the clinical variable used. The factorial analysis showed a construct of 4 factors that were only moderately similar to the original structure of the questionnaire, due mainly to inclusion of a small number of questions with conditioned response and others with low discriminatory capacity. CONCLUSIONS: The SGRQ shows excellent concurrent and predictive internal consistency and validity, though restructuring of the original construct would be advisable before use in patients with stable bronchiectasis.

Aged↗

PubMed1998

Quantification of insulin-like growth factor-1 (IGF-1) mRNA: development and validation of an internally standardised competitive reverse transcription-polymerase chain reaction.

To investigate the role of local IGF-1 mRNA expression in various tissues, we developed and validated a method which allows for a specific, sensitive and reliable quantification of IGF-1 mRNA: an internally standardised Reverse Transcription-Polymerase Chain Reaction (RT-PCR). A synthetic competitive template IGF-I standard cRNA (IGF-1 cRNA) was designed, which contains the same flanking primer sequences used to amplify the wild type IGF-1 mRNA, but differs by 56 bp in length. To obtain the IGF-1 mRNA concentration present in tissue RNA samples, series of 250 ng total-RNA were spiked with three known quantities of the standard IGF-1 cRNA, incubated for competitive RT-PCR reactions and the two amplificates obtained (184 bp from IGF-1 cRNA and 240 bp from the wild type IGF-I mRNA) were subsequently separated and quantified by HPLC-UV. For every individual tissue RNA sample, the ratio R (R = competitor PCR product / wild type PCR product) was plotted against the number of starting molecules of the competitor IGF-1 cRNA. The initial amount of IGF-1 mRNA present in the sample can then be read off where R = 1. The validated assay had a detection limit of 1600 IGF-1 cRNA molecules/reaction, the intra-assay variation was 7.4% (n = 5) and linearity (r = 0.997) was given between 140 ng to 840 ng total-RNA input. The present method was first applied to study the effect of long term castration on the IGF-1 expression rates in bovine tissues. The hepatic IGF-1 mRNA concentrations were well correlated (r = 0.81) with the plasma concentrations as quantified by RIA and were higher in intact than in castrated animals. In two skeletal muscles (m. splenius and m. gastrocnemius) IGF-1 mRNA concentrations were 20- and 35- times lower than in liver, respectively, without any differences between steers and bulls. In bulls, the IGF-1 mRNA expression was higher in m. splenius (p < 0.01) than m. gastrocnemius, indicating that locally produced IGF-1 might be important for sexually dimorphic muscle growth patterns.

Animals↗

PubMed1995

Validation of the 'internal reference technique' for calibrating microdialysis catheters in situ.

In vivo calibration of microdialysis catheters with [3H]glucose as internal reference was done in rat (n = 17) and human (n = 12) subcutaneous tissue. The estimated interstitial glucose level was compared with the glucose concentration in venous plasma which, in turn, has been shown to be identical to the interstitial glucose concentration. In subcutaneous tissue of anaesthetized male Sprague-Dawley rats, interstitial glucose was significantly overestimated (43%, P < 0.005, n = 8, and 19%, P < 0.005, n = 9, in normoglycaemic and hyperglycaemic animals, respectively). Furthermore, fractional outflux of [3H]glucose decreased continuously during prolonged perfusion of the microdialysis catheter. In contrast, in human subcutaneous tissue microdialysed with two catheters, correct measurements of interstitial glucose could be achieved and the precision was comparable to that obtained with equilibration calibration in vivo. The average relative error of the mean result of two catheters was 8.9% at a perfusate flow rate of 1 microL min-1. It may be suggested that calibration in vivo of microdialysis catheters with internal references may be used in human subcutaneous tissue. However, it is necessary to validate the calibration technique in each different tissue under reproducible experimental conditions since accumulation of the reference substance in the tissue may create artefactual results.

Adipose Tissue↗

PubMed1993

The SF36 health survey questionnaire: an outcome measure suitable for routine use within the NHS?

OBJECTIVE: To assess the validity, reliability, and acceptability of the short form 36 (SF 36) health survey questionnaire (a shortened version of a battery of 149 health status questions) as a measure of patient outcome in a broad sample of patients suffering from four common clinical conditions. DESIGN: Postal questionnaire, followed up by two reminders at two week intervals. SETTING: Clinics and four training practices in north east Scotland. SUBJECTS: Over 1700 patients aged 16-86 with one of four conditions--low back pain, menorrhagia, suspected peptic ulcer, or varicose veins--and a comparison sample of 900 members of the general population. MAIN OUTCOME MEASURES: The eight scales within the SF36 health profile. RESULTS: The response rate exceeded 75% in the patient population (1310 respondents). The SF36 satisfied rigorous psychometric criteria for validity and internal consistency. Clinical validity was shown by the distinctive profiles generated for each condition, each of which differed from that in the general population in a predictable manner. Furthermore, SF36 scores were lower in referred patients than in patients not referred and were closely related to general practitioners' perceptions of severity. CONCLUSIONS: These results provide support for the SF36 as a potential measure of patient outcome within the NHS. The SF36 seems acceptable to patients, internally consistent, and a valid measure of the health status of a wide range of patients. Before it can be used in the new health service, however, its sensitivity to changes in health status over time must also be tested.

Adolescent↗

PubMed2005

Impact of participant and physician intervention preferences on randomized trials: a systematic review.

CONTEXT: Allocation on the basis of randomization rather than patient choice is the gold standard of unbiased estimates of efficacy in clinical medicine. However, randomly allocating patients to treatments that do not accord with their preferences may influence internal and external validity. OBJECTIVE: To determine whether preferences affect recruitment to trials (external validity) and outcomes in trials (internal validity). DATA SOURCES: We searched MEDLINE, EMBASE, PsycINFO, CINAHL, AMED, and the Cochrane Library for articles published between 1966 and September 2004. We also hand-searched several major medical journals, searched reference lists of relevant articles, and contacted authors of published preference designs. The 2 themes in the first filter of the search strategy were preferences and possible determinants of preferences. STUDY SELECTION: Comprehensive cohorts and 2-stage trials that measured or recorded patient or physician preference, included allocation of participants to random and preference cohorts, and followed up all participants. We excluded trials with no recording of preference; of decision aids; with measurements of preferences for economic analyses; in which patients who refused randomization were followed up without reference to preferences; and of nonclinical populations. DATA EXTRACTION: Up to 4 reviewers independently evaluated the articles, and disagreements were resolved at project steering group meetings. We extracted data on study design, measurement of preference, recruitment, attrition, and summary data on the primary outcome(s) at baseline and each follow-up point. DATA SYNTHESIS: Of 10,023 citations identified, 170 articles met screening criteria and 32 (27 comprehensive cohorts and 5 two-stage trials) were determined to be eligible and were used in the final review. Although treatment preferences led to a substantial proportion of people refusing randomization, there was less evidence of bias in the characteristics of individuals agreeing to be randomized. Differences in outcome across the trials between randomized and preference groups were generally small, particularly in large trials and after accounting for baseline measures of outcome. Therefore, there was little evidence that preferences substantially interfere with the internal validity of randomized trials. CONCLUSIONS: Preferences influence whether people participate in randomized trials, but there is little evidence that they significantly affect validity.

Humans↗

PubMed2005

Validation of the International Study of Asthma and Allergies in Children (ISAAC) and U.K. criteria for atopic eczema in Ethiopian children.

BACKGROUND: Reliable diagnostic criteria for atopic eczema (AE) are essential in order to make international comparisons and to identify possible disease risk factors. Little is known about the prevalence of atopic eczema and validity of diagnostic criteria for AE in developing countries where English is not the first language. OBJECTIVES: We sought to determine the prevalence of AE in an area of urban and rural Ethiopia, and to compare the predictive values of different questionnaire and examination methods for diagnosing AE in this population. METHODS: We conducted a cross-sectional survey of 7915 children aged 1-5 years living in and around the town of Jimma in southwest Ethiopia. AE prevalence was assessed in two ways: (i) by using the International Study for Asthma and Allergies in Childhood (ISAAC) questionnaire, and (ii) using the U.K. refinement of Hanifin and Rajka's diagnostic criteria. All possible cases identified by screening questions and random samples of controls were then examined by an experienced local paediatrician, who acted as a reference standard to determine the predictive value of the criteria used to diagnose AE. RESULTS: The overall 1-year period prevalence of AE according to ISAAC and U.K. criteria was 4.4%[95% confidence interval (CI) 3.95-4.85] and 1.8% (95% CI 1.5-2.1), respectively. Corresponding point prevalence estimates (symptoms in the last week) were 1.8% for ISAAC and 1.3% for the U.K. criteria. The positive predictive values of the ISAAC and U.K. criteria questions for AE symptoms still reported to be present (in the last week) at the doctor's examination were 48.8% and 55.5%, respectively. Corresponding negative predictive values were 90.5% and 90.1%, respectively. The sign of visible flexural dermatitis (a component of the U.K. criteria) when used alone had positive and negative predictive values of 57% and 91%, respectively. CONCLUSIONS: Neither the ISAAC nor U.K. criteria performed especially well in predicting cases of AE in this survey. Possible reasons include problems with questionnaire translation, cultural conceptions of terminology, asking parents rather than the child about symptoms, the transient nature of AE signs, and differences in what a doctor perceives to constitute a typical case of AE. The results do not preclude the use of standardized diagnostic criteria alongside a doctor's examination in future surveys of Ethiopian children, and knowledge of the criteria's limited predictive value should help to interpret study findings that have employed such criteria. Consideration should be given to adopting the sign of visible flexural dermatitis as a standard for estimating the point prevalence of AE throughout the world because it is less susceptible to problems with translation and interpretation.

Age Distribution↗

PubMed1993

Validity of the International Headache Society criteria for migraine. GRIM. Groupe de Recherche Interdisciplinaire sur la Migraine.

For general practitioners and in epidemiological studies, migraine poses diagnostic problems. It is a polymorphous disease, with diagnosis based on a subjective description of symptoms. The International Headache Society (IHS) proposed a set of rigorous criteria for the diagnosis of migraine. We studied its validity on 171 outpatients of headache clinics and on 96 headache sufferers detected during an annual checkup for workers. The criteria showed an excellent specificity, however sensitivity in both samples was < 50%. This lack of validity could be due to IHS criteria being too restrictive. We therefore elaborated and validated our own diagnostic tool, based on the IHS criteria, to a sensitivity of 95% and a specificity of 78%. We propose our tool for epidemiological studies.

Adolescent↗

PubMed2006

Development and usefulness of an instrument for the standard description and comparison of services for disabilities (DESDE).

OBJECTIVE: Mental health research has made significant progress in international comparison and instrument development. This study reports the adaptation of the European Service Mapping Schedule (ESMS) to the assessment of services for persons with disabilities. METHOD: Qualitative groups were used to develop the Description and Evaluation of Services for Disabilities in Europe (DESDE). The psychometric analysis of DESDE covered: feasibility, inter-rater reliability, descriptive validity and internal validity. A demonstration study was also carried out. RESULTS: Compared to the original ESMS, a new main branch and several sub-branches were added. We identified 826 services for persons with disabilities, which provided 1284 main types of care. The feasibility and reliability was good for the majority of codes. Only 6% of services were not properly classified. The Boolean factor analysis supported the internal validity of DESDE. CONCLUSION: DESDE is a useful and reliable instrument for the assessment of services for persons with disabilities.

Disability Evaluation↗

PubMed2003

Validation of the International Restless Legs Syndrome Study Group rating scale for restless legs syndrome.

BACKGROUND: There is a need for an easily administered instrument which can be applied to all patients with restless legs syndrome (RLS) to measure disease severity for clinical assessment, research, or therapeutic trials. The pathophysiology of RLS is not clear and no objective measure so far devised can apply to all patients or accurately reflect severity. Moreover, RLS is primarily a subjective disorder. Therefore, a subjective scale is at present the optimal instrument to meet this need. METHODS: Twenty centers from six countries participated in an initial reliability and validation study of a rating scale for the severity of RLS designed by the International RLS study group (IRLSSG). A ten-question scale was developed on the basis of repeated expert evaluation of potential items. This scale, the IRLSSG rating scale (IRLS), was administered to 196 RLS patients, most on some medication, and 209 control subjects. RESULTS: The IRLS was found to have high levels of internal consistency, inter-examiner reliability, test-retest reliability over a 2-4 week period, and convergent validity. It also demonstrated criterion validity when tested against the current criterion of a clinical global impression and readily discriminated patient from control groups. The scale was dominated by a single severity factor that explained at least 59% of the pooled item variance. CONCLUSIONS: This scale meets performance criteria for a brief, patient completed instrument that can be used to assess RLS severity for purposes of clinical assessment, research, or therapeutic trials. It supports a finding that RLS is a relatively uniform disorder in which the severity of the basic symptoms is strongly related to their impact on the patient's life. In future studies, the IRLS should be tested against objective measures of RLS severity and its sensitivity should be studied as RLS severity is systematically manipulated by therapeutic interventions.

Adult↗