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PubMed2003

[Internal validity in cross-sectional studies: comments based on an investigation on the association between socioeconomic factors and schistosomiasis].

The purpose of this paper was to make some comments on validity based on an investigation developed in an urban area in the Greater Metropolitan Area of Recife, Brazil, the objective of which was to study the association between socioeconomic factors and schistosomiasis. It discusses the distortion in the odds ratio that may be introduced either by the way individuals are selected for the study or by the way the information is collected. The article describes the mechanisms used by the authors to avoid bias when planning or conducting the investigation and considerations were made on how these types of bias could have influenced the results.

English Abstract↗
PubMed2000

The problems of internal validation without a theoretical context: the different conceptual underpinnings of psychopathy and the disruptive behavior disorder criteria.

G. L. Burns (2000) has concluded that the Psychopathy Screening Device's content is limited because it contains items that overlap with criteria for several disorders in the Diagnostic and Statistical Manual of Mental Disorders (DSM). The problem with G. L. Burns's analysis is that it was conducted without an adequate understanding or specification of the conceptual underpinnings of either the construct of psychopathy or the constructs assessed by the DSM criteria. This reply attempts to clarify these conceptual frameworks to illustrate that to judge the adequacy of the content of a measure of psychopathy by comparing it with DSM criteria is inconsistent with the differing theoretical frameworks underlying these classification systems. Forcing measures of psychopathy to be designed around DSM criteria leads to inadequate measures of psychopathy and can limit advances both in our understanding of developmental precursors to psychopathy and in the classification of DSM disorders.

Antisocial Personality Disorder↗
PubMed1994

Sensitivity to change of 3 Systemic Lupus Erythematosus Disease Activity Indices: international validation.

OBJECTIVE: Three indices, the SLE Disease Activity Index (SLEDAI), the Systemic Lupus Activity Measure (SLAM) and the British Isles Lupus Assessment Group (BILAG), have been found to be reliable and valid measures of disease activity in patients with systemic lupus erythematosus (SLE). Our aim was to investigate their use and comparative ability to assess change in disease activity over time. METHODS: Clinical and laboratory features of 8 patients with SLE on each of 3 consecutive visits were abstracted and sent in 3 separate packages to physicians from 8 centers. The order of the patient visit summaries was randomized, and the 3 indices rated in one of 6 specific sequences. RESULTS: The 3 indices were significantly (p < 0.01) correlated: SLEDAI/SLAM = 0.61, BILAG/SLAM = 0.55, SLEDAI/BILAG = 0.35. The sequence presented, the order of patients and order of index scoring did not contribute significantly (p > 0.05) to the variation of any of the 3 indices. All 3 indices detected differences among patients (p < 0.01). Differences between visits were detectable with SLEDAI (p = 0.04) but not with SLAM or BILAG: CONCLUSION: Our study confirms that the SLEDAI, SLAM and BILAG are comparable disease activity measures. SLEDAI appears to be sensitive to change in disease activity over time.

Computers↗
PubMedDate not supplied

International validation study for the determination of chloramphenicol in bovine muscle.

A gas chromatographic (GC) procedure for the quantitation and GC/negative ion chemical ionization mass spectrometric (NICIMS) confirmation of chloramphenicol in calf muscle tissue was the subject of a validation study. Five analysts representing 5 laboratories in 4 countries participated in the quantitative method and analyzed 7 randomly numbered blind triplicates at 4 fortified and 3 incurred tissue concentrations on 3 separate days. The chloramphenicol concentrations ranged from 0 to 2.5 ppb. All data were reported to 3 significant figures. The coefficients of variation were 9.5-28.7% for repeatability and 14.6-38% over the study range for reproducibility. NICIMS data representing 3 laboratories in 3 countries successfully confirmed chloramphenicol in samples at 0.6 ppb or greater with no false positives in blank tissues.

Animals↗
PubMed1993

[Internal validation of a measurement scale: relation between principal component analysis, Cronbach's alpha coefficient and intra-class correlation coefficient].

The objective is to establish a simple relationship between two frequently used validation techniques which have been developed in the literature along the same lines: Principal Component Analysis and Cronbach's alpha. We have shown that under certain conditions, it is possible to estimate the reliability by using the results of a Principal Component Analysis only. Moreover, we report the relation between Cronbach's alpha and intraclass correlation coefficient, which are both used to estimate the reliability of continuous measures.

Data Interpretation, Statistical↗
PubMed2002

Bias and causal associations in observational research.

Readers of medical literature need to consider two types of validity, internal and external. Internal validity means that the study measured what it set out to; external validity is the ability to generalise from the study to the reader's patients. With respect to internal validity, selection bias, information bias, and confounding are present to some degree in all observational research. Selection bias stems from an absence of comparability between groups being studied. Information bias results from incorrect determination of exposure, outcome, or both. The effect of information bias depends on its type. If information is gathered differently for one group than for another, bias results. By contrast, non-differential misclassification tends to obscure real differences. Confounding is a mixing or blurring of effects: a researcher attempts to relate an exposure to an outcome but actually measures the effect of a third factor (the confounding variable). Confounding can be controlled in several ways: restriction, matching, stratification, and more sophisticated multivariate techniques. If a reader cannot explain away study results on the basis of selection, information, or confounding bias, then chance might be another explanation. Chance should be examined last, however, since these biases can account for highly significant, though bogus results. Differentiation between spurious, indirect, and causal associations can be difficult. Criteria such as temporal sequence, strength and consistency of an association, and evidence of a dose-response effect lend support to a causal link.

Bias↗
PubMed1986

The endogenous sub-type of depression: a study of its internal construct validity.

The internal construct validity of the endogenous sub-type of major depression was investigated by statistically modelling the RDC endogenous and DSM-III melancholia diagnostic criteria. Data consisted of symptom ratings on 788 patients with major depression from NIMH Collaborative Depression Study. Results indicated that the symptoms in the criteria do not specify a dichotomous classification, melancholic-non-melancholic or endogenous-nonendogenous. Results did support the existence of two sub-typings, one related to anhedonia, and one related to vegetative symptoms. The vegetative sub-type rarely occurred in non-anhedonic patients. Previous studies may have found support for a simple endogenous sub-type because of this hierarchical relationship and as a result of methodological differences.

Body Weight↗
PubMed2026

The potential of clustering methods for pre-test triage in sleep medicine: A systematic review.

Sleep disorders exhibit substantial heterogeneity, and traditional classifications may not fully capture clinically relevant subtypes. Clustering techniques can identify patient subgroups that improve phenotypic characterization and may support personalized management. This systematic review evaluated the application of clustering in sleep medicine, with particular focus on its potential use as a pre-test triage tool prior to formal sleep testing. PubMed/MEDLINE, Embase, Web of Science, and Scopus were searched to February 2025. Eligible studies applied clustering to classify sleep disorders in adults. Two reviewers independently conducted screening, data extraction, and risk-of-bias assessment using QUADAS-2. The protocol was registered on PROSPERO. Fifty-one studies (1983-2025) were included, predominantly focused on obstructive sleep apnea (OSA) (n&#x202f;=&#x202f;38, 74%). Hierarchical clustering (n&#x202f;=&#x202f;20) and K-means clustering (n&#x202f;=&#x202f;14) were the most frequently used techniques. Internal validation was reported in only 18% of studies, and external validation was reported in only 1 study. Seven studies relied exclusively on baseline clinical, demographic, or questionnaire data, representing pre-test scenarios, whereas most incorporated polysomnography-derived variables, limiting their applicability to early clinical stratification. Hierarchical clustering was the most commonly applied method; however, the overall lack of validation limits confidence in the robustness and clinical applicability of identified phenotypes. The potential role of clustering as a pre-test triage strategy remains largely unexplored, as most studies focused on post-diagnostic phenotyping and were affected by incorporation bias. Future research should prioritize pre-test clinical variables, rigorously validate internally and externally, and adopt standardized methodological and reporting practices to facilitate clinical translation.

Humans↗
PubMed2000

Case study methodology in tissue viability. Part 1: Methodological considerations.

Case studies are often presented in relation to tissue viability problems. Within hierarchies of evidence, case studies are sometimes seen to be on a par with expert opinion. This paper examines the case study as a research method and seeks to determine its value in tissue viability research. The term 'case study' denotes a general strategy for research where several methods of data collection are used to provide an in-depth analysis of an individual, group or institution. Three types of case study are used in research: intrinsic, instrumental and collective. All case studies utilize data triangulation within their design, that is, the use of a variety of sources of data within a study. It is one of the major strengths of the case study method. Data sources include documentary data sources, observation and interviews. As in any research, validity and reliability are important in case study methodology; in particular, construct validity, internal validity and external validity. Case studies are potentially vulnerable to observer error and observer bias. Examples are given of potential case studies in tissue viability and their strengths and weaknesses. If undertaken prospectively, with clearly defined multiple sources of data collection and a documented chain of evidence, case studies can add breadth to our knowledge and experience of caring for patients with tissue viability problems.

Data Collection↗
PubMed1997

Problems and solutions in longitudinal research: from theory to practice.

Longitudinal studies provide the only method for directly studying the natural course of human growth and development and are therefore invaluable, both to public health and clinical medicine. However, longitudinal studies are accompanied by specific problems. The purpose of this final paper is to discuss in two separate sections some of the methodological, analytical and practical issues regarding the relevance of the findings reported. Examples of such problems and their solutions are described. Methodological issues discussed concern statistical conclusion validity, internal validity and construct validity of longitudinal studies. Practical issues discussed concern the design of longitudinal studies, the recruitment and retention of subjects, and the methods used. Finally, examples of the significance of longitudinal research outcomes to public health and clinical medicine are given.

Clinical Medicine↗
PubMed2000

The use of conjoint analysis to elicit community preferences in public health research: a case study of hospital services in South Australia.

AIMS: To demonstrate the use of conjoint analysis (CA) in public health research through a survey of the South Australian community about aspects of their public hospital services. METHODS: A series of focus groups determined the most important attributes in choice of hospital services. These were built into a CA survey, using the discrete choice approach. The survey was posted to a representative sample of 700 South Australians. Theoretical validity, internal consistency and non-response bias were all investigated. RESULTS: Some 231 individuals returned the questionnaire. The attribute, 'improvement in complication rates' was positively associated with choice of hospital. Three attributes were found to be negatively associated with such choice: 'waiting times for casualty', 'waiting times for elective surgery' and, anomalously, 'parking and transport facilities'. 'Travel time' and the cost attribute, 'Medicare levy' were not statistically significant. Trade-offs between the significant attributes were estimated, as were satisfaction or utility scores for different ways of providing hospital services. Results concerning internal consistency and internal validity were encouraging, but some potential for non-response bias was detected. CONCLUSION: A high premium is placed on the quality of hospital care and members of the community are prepared to choose between hospitals largely on the basis of outcomes and length of waiting times for elective surgery and in casualty. IMPLICATIONS: CA can yield potentially policy-relevant information about community preferences for health services.

Adult↗
PubMed2001

Clinical practice guidelines for the care and treatment of breast cancer: 13. Sentinel lymph node biopsy.

OBJECTIVE: To provide information and recommendations to women with breast cancer and their physicians regarding what is now known about sentinel lymph node (SLN) biopsy. OPTIONS: Axillary dissection; SLN biopsy followed by backup axillary dissection; SLN biopsy. OUTCOMES: Accurate determination of cancer stage, resulting in better-informed therapeutic decisions. EVIDENCE: Systematic review of English-language literature published from January 1991 to December 2000 retrieved primarily from MEDLINE and CANCERLIT. RECOMMENDATIONS: Axillary dissection is the standard of care for the surgical staging of operable breast cancer. If a patient requests or is offered SLN biopsy, the benefits and risks as well as what is and is not known about the procedure should be outlined. Patients should be informed of the number of SLN biopsies performed by the surgeon and the surgeon's success rate with the procedure, as determined by the identification of the SLN and the false-negative rate (the presence of tumour cells in the axillary nodes when the SLN biopsy result is negative). Before surgeons replace axillary dissection by SLN biopsy as the staging procedure at their institution, they should (a) familiarize themselves with the literature on the topic and the techniques needed to perform the procedure, (b) follow a defined protocol for all 3 aspects of the procedure (nuclear medicine, surgery, pathology) and (c) perform backup axillary dissection until an acceptable success rate (as determined by the identification of the SLN and the false-negative rate) is achieved. A surgeon who performs breast cancer surgery infrequently should not perform SLN biopsy. A positive SLN biopsy result or failure to identify an SLN should prompt full axillary dissection. SLN biopsy is contraindicated in women who have clinically palpable nodes, locally advanced breast cancer, multifocal tumours, previous breast surgery or previous irradiation of the breast. Staining of tissue sections with hematoxylin and eosin, and not immunohistochemical analysis for cytokeratin, should determine adjuvant therapy. Participation in randomized clinical trials is encouraged. [A patient version of these guidelines appears in Appendix 1.] VALIDATION: Internal validation within the Steering Committee on Clinical Practice Guidelines for the Care and Treatment of Breast Cancer; no external validation.

Axilla↗
PubMed2002

Clinical practice guidelines for the care and treatment of breast cancer: 14. The role of hormone replacement therapy in women with a previous diagnosis of breast cancer.

OBJECTIVE: To provide information and recommendations to women with a previous diagnosis of breast cancer and their physicians regarding hormone replacement therapy (HRT). OUTCOMES: Control of menopausal symptoms, quality of life, prevention of osteoporosis, prevention of cardiovascular disease, risk of recurrence of breast cancer, risk of death from breast cancer. EVIDENCE: Systematic review of English-language literature published from January 1990 to July 2001 retrieved from MEDLINE and CANCERLIT. RECOMMENDATIONS: * Routine use of HRT (either estrogen alone or estrogen plus progesterone) is not recommended for women who have had breast cancer. Randomized controlled trials are required to guide recommendations for this group of women. Women who have had breast cancer are at risk of recurrence and contralateral breast cancer. The potential effect of HRT on these outcomes in women with breast cancer has not been determined in methodologically sound studies. However, in animal and in vitro studies, the development and growth of breast cancer is known to be estrogen dependent. Given the demonstrated increased risk of breast cancer associated with HRT in women without a diagnosis of breast cancer, it is possible that the risk of recurrence and contralateral breast cancer associated with HRT in women with breast cancer could be of a similar magnitude. * Postmenopausal women with a previous diagnosis of breast cancer who request HRT should be encouraged to consider alternatives to HRT. If menopausal symptoms are particularly troublesome and do not respond to alternative approaches, a well-informed woman may choose to use HRT to control these symptoms after discussing the risks with her physician. In these circumstances, both the dose and the duration of treatment should be minimized. VALIDATION: Internal validation within the Steering Committee on Clinical Practice Guidelines for the Care and Treatment of Breast Cancer; no external validation. SPONSOR: The steering committee was convened by Health Canada. COMPLETION DATE: October 2001.

Animals↗
PubMed1995

Questions from practice: a basis for research.

Occupational health nurses in clinical practice are in an excellent position to identify unanswered questions that affect the health and well being of employees. Once these questions have been asked, the occupational health nurses may proceed with structured research to find answers. The research begins with a thorough review of existing literature to learn the background of the issue and clearly define a research question. This question is then framed conceptually to guide the study. The theoretical framework may be supported or refuted by the research project. The study method is dictated by the research question and the theoretical framework. Two basic research methods are intervention and descriptive studies. Intervention studies, with treatment and control groups, attempt to show differences between groups when one receives a certain treatment and the other group does not. Descriptive studies generally survey attitudes or activities, then test for associations. Data analysis is determined by the type of study and type of data collected. Descriptive statistics generate frequencies and correlations; inferential statistics yield stronger information about associations of the variables. Interpretation of research findings must include consideration of threats to validity. Internal validity allows the investigator to state with confidence that the intervention was responsible for the difference between the groups. External validity allows for generalizability of the findings to other populations. The purpose of nursing research is to advance the discipline of nursing. Research refines nursing theories and guides practice. It is through research that occupational health nurses gain confidence to alter procedures and provide interventions that have been shown to be effective.

Clinical Nursing Research↗
PubMedDate not supplied

Using in vitro prediction models instead of the rabbit eye irritation test to classify and label new chemicals: a post hoc data analysis of the international EC/HO validation study.

The international validation study on alternative methods to replace the Draize rabbit eye irritation test, funded by the European Commission (EC) and the British Home Office (HO), took place during 1992-1994, and the results were published in 1995. The results of this EC/HO study are analysed by employing discriminant analysis, taking into account the classification of the in vivo data into eye irritation classes A (risk of serious damage to eyes), B (irritating to eyes) and NI (non-irritant). A data set for 59 test items was analysed, together with three subsets: surfactants, water-soluble chemicals, and water-insoluble chemicals. The new statistical methods of feature selection and estimation of the discriminant functions classification error were used. Normal distributed random numbers were added to the mean values of each in vitro endpoint, depending on the observed standard deviations. Thereafter, the reclassification error of the random observations was estimated by applying the fixed function of the mean values. Moreover, the leaving-one-out cross-classification method was applied to this random data set. Subsequently, random data were generated r times (for example, r = 1000) for a feature combination. Eighteen features were investigated in nine in vitro test systems to predict the effects of a chemical in the rabbit eye. 72.5% of the chemicals in the undivided sample were correctly classified when applying the in vitro endpoints lgNRU of the neutral red uptake test and lgBCOPo5 of the bovine opacity and permeability test. The accuracy increased to 80.9% when six in vitro features were used, and the sample was subdivided. The subset of surfactants was correctly classified in more than 90% of cases, which is an excellent performance.

Animal Testing Alternatives↗
PubMed1998

Methodological issues in the application of conjoint analysis in health care.

This paper adds to an increasing literature on methodological questions addressed in the application of conjoint analysis (CA) in health care. Three issues are addressed: ordering effects; internal validity; and internal consistency. The results of an application of CA in a primary care setting provide no evidence that the ordering of scenarios was important. Evidence was found of both internal validity and internal consistency. In addition, individual preferences were found to be determined by experiences, which raise potentially important questions regarding the elicitation and use of such preferences in economic evaluation.

Appointments and Schedules↗