Search

The Q-matrix is commonly used in diagnostic classification models and has recently been incorporated into the multidimensional item response theory (MIRT) models to add information about the relati...

We investigate the relationship between Bayesian inference networks (BayesNets) and diagnostic classification models (DCMs). Specifically, we demonstrate and empirically examine the equivalency of parameterizations between BayesNets and DCMs. Then, we propose a model-comparison framework for testing the model fit of BayesNets, in which we show how BayesNets are nested within the saturated DCM structural models. Additionally, we show when attributes feature a linear hierarchy, the Hierarchical DCM is nested within both BayesNets and saturated DCMs. The usefulness of proposed framework and model-fit testing strategy was supported by the results of analyzing both simulated and empirical data.

Purpose Fabry disease belongs to lysosomal storage disorders and can be successfully treated today. On the contrary, the correct diagnostic classification of its symptoms can be challenging and most patients suffer from pain for years, until they are diagnosed correctly. The aim of this project was to characterize patients with unclassified extremity pain and to present a simple algorithm for a retrospective stratification approach. Patients and methods The FabryScan includes a bedside-test and a questionnaire, consisting of 10 symptom-orientated and anamnestic questions. For the stratification of patients according to the likelihood for Fabry disease two different approaches were conducted. First, a prospective subgrouping based on the previously invented FabryScan evaluation system was conducted. The second retrospective approach consisted of a factor analysis and a subsequent two-way cluster analysis. Further on, 4 patients diagnosed with Fabry disease were stratified according to both approaches. Results In total, 183 completed datasets were included in the statistical analysis. The first approach prospectively classified patients into 3 subgroups (n=40 [likely], n=96 [possible], n=47 [unlikely]) according to the FabryScan evaluation system. The second approach retrospectively stratified patients into 3 subgroups (n=47 [cluster 1], n=95 [cluster 2], n=41 [cluster 3]). Finally, the Fabry patients were sorted to the subgroups, indicative for the highest possibility of Fabry disease in both stratification approaches A and B. Conclusion Both stratification approaches sorted patients with confirmed Fabry disease to the subgroups, indicative for the highest likelihood for Fabry. These results indicate validity of the initially selected FabryScan outcome parameters.

Background Despite improvements in neonatal cardiac surgery and postoperative care, hospitalized death for infants with low birth weight remains high. Objective This study sought to identify predictors of postoperative outcomes in low-birth-weight infants undergoing congenital heart surgery and establish nomograms to predict postoperative intensive-care unit (ICU) stay. Methods From June 2009 to June 2018, a retrospective review of 114 infants with low birth weight (≤2.5 kg) undergoing congenital heart surgery was conducted at Guangdong Provincial People's Hospital. Purely surgical ligation of patent ductus arteriosus was excluded from this study. A total of 26 clinical variables were chosen for univariate, multivariate, and Cox regression analysis, and 14 variables were analyzed as predictors of postoperative outcomes. Nomograms were established to predict risk of postoperative cardiac ICU (CICU) stay, postoperative neonatal ICU (NICU) stay, and total ICU length of stay in infants with cardiac diseases. Results Two variables were independent predictors in multiple logistic regression analysis of hospitalized death: operation weight and Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery (STAT) risk categories. Six variables were independent predictors in the Cox model of postoperative ICU length of stay, including sex, prematurity, birth weight, preoperative stay time in NICU, diagnostic classification, and STAT risk categories. We calculated concordance-index values to estimate the discriminative ability of models of risk of postoperative CICU stay, postoperative NICU stay, and total ICU length of stay, with values of 0.758 (95% CI 0.696-0.820), 0.604 (95% CI 0.525-0.682), and 0.716 (95% CI 0.657-0.776), which indicated the possibility of true-positive results. Conclusion Our findings might help clinicians predict postoperative outcomes and optimize therapeutic strategies.

More than three decades after their introduction, diagnostic classification models (DCM) do not seem to have been implemented in educational systems for the purposes they were devised. Most DCM research is either methodological for model development and refinement or retrofitting to existing nondiagnostic tests and, in the latter case, basically for model demonstration or constructs identification. DCMs have rarely been used to develop diagnostic assessment right from the start with the purpose of identifying individuals’ strengths and weaknesses (referred to as true applications in this study). In this article, we give an introduction to DCMs and their latest developments along with guidelines on how to proceed to employ DCMs to develop a diagnostic test or retrofit to a nondiagnostic assessment. Finally, we enumerate the reasons why we believe DCMs have not become fully operational in educational systems and suggest some advice to make their advent smooth and quick.

Over the last decade, advances in molecular and imaging-based biomarkers have induced a more versatile diagnostic classification and prognostic evaluation of glioma patients. This, in combination with a growing therapeutic armamentarium, enables increasingly individualized, risk-benefit-optimized treatment strategies. This path to precision medicine in glioma patients requires surgical procedures to be reassessed within multidimensional management considerations. This article attempts to integrate the surgical intervention into a dynamic network of versatile diagnostic characterization, prognostic assessment, and multimodal treatment options in the light of the latest 2016 World Health Organization (WHO) classification of diffuse brain tumors, WHO grade II, III, and IV. Special focus is set on surgical aspects such as resectability, extent of resection, and targeted surgical strategies including minimal invasive stereotactic biopsy procedures, convection enhanced delivery, and photodynamic therapy. Moreover, the influence of recent advances in radiomics/radiogenimics on the process of surgical decision-making will be touched.

Diagnostic classification models (DCMs) can provide multidimensional diagnostic feedback about students’ mastery levels of knowledge components or attributes. One advantage of using DCMs is the abi...

Diagnostic classification models (DCMs, also known as cognitive diagnosis models) hold the promise of providing detailed classroom information about the skills a student has or has not mastered. Sp...

We review the GIDNA and CDM packages in R for fitting cognitive diagnosis / diagnostic classification models. We first provide a summary of their core capabilities and then use both simulated and r...

Diagnostic classification models (DCMs) classify examinees based on the skills they have mastered given their test performance. This classification enables targeted feedback that can inform remedial instruction. Unfortunately, applications of DCMs have been criticized (e.g., no validity support). Generally, these evaluations have been brief and not the study’s focus. Thus, the literature of DCM applications was extensively analyzed. Results mostly supported criticisms. For example, most DCM applications lacked strong reliability and validity evidence and were not used to give feedback to examinees. We provide possible explanations for these results and suggest how to advance the application and usage of DCMs.

Evaluating test scores is an essential process, critical in both educational research and practice. To scientifically understand and utilize test scores, educators and researchers need to choose appropriate psychometric models to analyse and interpret assessment data. In this paper, we discuss two classes of psychometric models that have been widely used in educational measurement: item response theory (IRT) models and diagnostic classification models (DCMs). Specifically, the IRT discussion focuses on producing scores on a numerical continuum using the two-parameter logistic model. We then discuss methods for producing scores based on ordinal classifications with DCMs and compare and contrast such scores with those from IRT models. In addition, through step-by-step examples, we demonstrate how to obtain estimates from and interpret results from each model we present. We conclude the paper with considerations in and suggestions for choosing an appropriate psychometric model.

Reliance on a single informant method in the evaluation of autism spectrum disorder (ASD) can increase misclassification. Yet, current ASD screening instruments predominately rely on a single informant approach. This study combined scores from two ASD screening instruments, the clinician administered Autistic Behavioural Indicators Instrument (ABII) and its parent questionnaire equivalent (ABII-PQ), to examine whether a combination score improved ASD classification in a sample of children with ASD (n=51, Mchild age= 3.6 years, SD= 1.01, range = 2-6 years). Results showed the ABII and ABII-PQ were significantly associated, r= .62, p= .01, and did not differ significantly on final correct ASD classification. However, final agreement on ASD classification between instruments was poor, κ=.19, p=.184. One method of combining scores from the ABII and ABII-PQ significantly improved classification, correctly classifying 100% of children with ASD. Results show combining scores from parent and clinician rated screening instruments could improve ASD classification.

Background Having a child with intellectual disability impacts all family members, with both parents and siblings having to adjust. Negative impact on the typically developing sibling, specifically, has been shown to vary based on caregiving responsibilities and mothers’ stress level.Method This study gathered information from 238 Latina and Anglo mothers of young adults with intellectual disability to explore sibling negative impact related to maternal stress, positive feelings about parenting, sibling diagnostic category, and cultural group.Results Mothers experiencing more stress reported higher levels of sibling impact; mothers with more positive feelings about parenting reported lower levels of negative impact, with Latina mothers reporting higher levels of stress and positive feelings about parenting. Anglo mothers, however, were less likely to designate a sibling as a future caregiver.Conclusions These findings suggest culture and diagnostic classification should be given more attention rel...

The publication of DSM-5 has been accompanied by a fair amount of controversy. Amongst DSM’s most vocal ‘insider’ critics has been Thomas Insel, Director of the US National Institute of Mental Health. Insel has publicly criticised DSM’s adherence to a symptom-based classification of mental disorder, and used the weight of the NIMH to back a rival research strategy aimed at a more biology-based diagnostic classification. This strategy is part of Insel’s vision of a future, more preventative psychiatry in which mental disorders are not only understood as biological disorders of the brain, but also as neurodevelopmental disorders. This paper examines the interest and merit of Insel’s views of mental and neurodevelopmental disorder for the philosophy of psychopathology, with a special focus of his neurodevelopmental model of schizophrenia. Pitman’s ‘moderate materialism’ will be used both as a philosophical lens through which to examine Insel’s position, as well as an example of a philosophical framework that may require updating and revision in the light of moves towards a neurodevelopmental conception of mental disorder. South African Journal of Philosophy 2014, 33(2): 131–144

In Unique Characteristics of Diagnostic Classification Models: A Comprehensive Review of the Current State-of-the-Art, Rupp and Templin (2008 hereafter RT) undertake the ambitious task of providing...

In their paper Unique Characteristics of Diagnostic Classification Models: A Comprehensive Review of the Current State-of-the-Art, Andre Rupp and Jonathan Templin (2008) provide a comparative analy...

Rupp & Templin (2008) have done a remarkable job with their paper. The overview tries and to a large extent succeeds in being a balanced one—one that does not only include developments originating ...

Rupp and Templin (2008) provide an extensive review of the literature on diagnostic classification models (DCMs). They provide a multidisciplinary audience with a valuable attempt to define and cla...

Educational and psychological measurement are undergoing significant development and change as interdisciplinary forces stemming from cognitive science, instructional technology, mathematical stati...

What is the nature of latent predictors that facilitate diagnostic classification? Rupp and Templin (this issue) suggest that these predictors should be multidimensional, categorical variables that...

As psychoanalytic clinicians, we do not believe that assessment should be diagnosis based. However, we are supportive of attempts to create a diagnostic classification system that reflects something essential about human nature and also serves clinical purposes. In this article, we present a psychoanalytic diagnostic scheme that combines a more descriptive characterological diagnosis with a more structural level of personality organization diagnosis. The scheme is applied to a clinical case and then we discuss it in terms of the functions such a scheme provides for assessment.

Diversity in nomenclature and on-going dilemmas over the conceptual bases for the classification of voice disorders make it virtually impossible for the collation and accurate comparison of evidence-based data across different clinical settings. This has significant implications for treatment outcome studies. The first aim of this study was to develop a modified diagnostic classification system for voice disorders with clearly defined operational guidelines by which we might reliably distinguish voice disorders from one another. The second aim was to establish the face validity and reliability of the system as an effective diagnostic tool for the allocation of patients to different diagnostic groups for clinical and research purposes. After the Diagnostic Classification System for Voice Disorders (DCSVD) had been developed, it was used in an inter-rater reliability study for the independent assessment of 53 new consecutive patients referred to the Voice Analysis Clinics of three tertiary hospitals. There were three raters present for the assessment and diagnostic allocation of each patient. The high levels of inter-rater reliability suggest this may be a robust classification system that has good face validity and even at this early stage, strong construct validity.

A previous study compared socio-demographic characteristics, health problem characteristics, and primary process data between a database sample of patients referred to physical therapy (PT) versus a sample of patients referred for specific manual physical therapy (MPT) diagnosis and management. This study did not differentiate between patients based on affected body region or diagnosis. The present study is a secondary analysis of these data for patients with non-specific low-back pain (LBP). Statistical analysis indicated that the MPT patient sample was significantly (P

The diagnostic validity of new demographically corrected WAIS-III norms was investigated using a sample of 100 patients with traumatic brain injury (TBI) and a matched control group from the standardization sample. Demographically corrected norms were compared to traditional age-corrected norms. Although education accounted for incremental variance in WAIS-III factor scores in patients with TBI, above and beyond the effects of injury severity, the demographically corrected norms did not yield statistically different diagnostic classification of individuals with moderate-severe TBI than the traditional norms. In participants with relatively low levels of educational attainment, sensitivity to length of coma was less for demographically corrected norms then for traditional age-corrected norms. Nevertheless, when using a discrepancy between Verbal Comprehension and Processing speed, diagnostic accuracy rates were again similar for both sets of norms. It is concluded that the demographically corrected WAIS-III norms do not offer a clear advantage or disadvantage compared to traditional age-corrected norms in the assessment of patients with TBI who are Caucasian and who have at least a middle school level of education.

Dizziness is a frequent complaint in patients presenting to orthopaedic physical therapists. Differential diagnosis of dizziness is complex but essential and requires knowledge of musculoskeletal, vestibular, cardiovascular, neurological, metabolic, and psychiatric conditions, thus transcending the musculoskeletal boundaries of orthopaedic physical therapy clinical practice. Physical therapy intervention is not indicated for many causes of dizziness. Some types of dizziness present contra-indications to certain orthopaedic physical therapy interventions. This article presents a diagnostic classification system and relevant pathophysiology that may facilitate orthopaedic physical therapy diagnosis, screening, and subsequent appropriate physical therapy management or medical referral.

The etiology of psychotic states is traced to dissociative elements in infantile emotional development, utilizing case examples from psychotherapeutic work with child and adult patients. A live infant observation is also reported, in which an infant manifests a dissociative reaction in the wake of a discrete trauma. Specific attention is devoted to the route of aggression in the psychotic case, as well as to the need of certain psychotic patients to find “stillness” in the treatment if there is to be hope for recovery. Issues relevant to the diagnostic classification of psychotic illness in children are also considered.

The accurate diagnosis of clinical conditions that include language disorders (e.g., developmental disabilities, autism, and specific language impairment) rests squarely on the accurate measurement of language and related abilities. In addition, because the goal of any treatment program is to generate measurable progress in language function, it is essential that treatment programs be designed within the context of state-of-the-art measurement. Therefore, both diagnosis and treatment of language disorders in children are founded on measurement. However, recent advances in the measurement of language abilities have outpaced changes in diagnostic classification and treatment methods. This should not imply that diagnosis be solely guided by available subtests on an intelligence battery or that treatment be designed primarily to teach the items used in measurement. Rather the goal should be to diagnose with an eye on the results of measurement and develop treatments that result in advances in the underlying s...

Diagnostic assessment is currently a very active research area in educational measurement. Literature related to diagnostic modeling has been in existence for several decades, but a great deal of r...

In general, I feel that diagnostic classification modeling (DCMs; also commonly referred to as cognitive diagnosis models) holds great potential in low stake situations because of the promise of pr...

Since their official introduction, the International Classification of Diseases, 10th Revision (ICD-10),1 and the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV),2 operational classification systems have largely become an integral part of the body of knowledge of psychiatrists throughout the world and instruments they constantly refer to. In this article I look at some of the questions that have been raised in connection with these classifications, both as a result of the growing number of critical analyses and of my own experience. This short contribution does not claim to provide exhaustive answers, but merely to stimulate further discussion. Psychiatrists probably all started adopting operational diagnostic classification systems, such as the ICD and DSM classifications, on the assumption that the reliability of the diagnoses therein defined was unequivocally demonstrated to be very high across the centers and even countries of evaluation, without realizing that the general consensus was based on the lowest level of validity conceivable, since it resulted from the mutual agreement of experts rather than on any proven facts concerning the etiology of mental disorders. This means that in the absence of biological markers for most psychopathological disorders, diagnostic features were based on clinical descriptions, resulting in “official” nosological groupings. One of the main objections raised by clinical psychiatrists was that in many instances diagnoses were based on the numbers of certain symptoms.3 Nevertheless, in spite of initial warnings of oversimplification, the two most widely used official classifications - DSM and ICD - came to be largely regarded as nosologically valid by medical doctors, official institutions, and even the public at large. The interesting, but logical, paradox is that those least satisfied with these so universally acclaimed classifications are probably the psychiatrists. In this article, I would like to briefly discuss two frequently asked questions: (i) what is the validity of the current diagnostic process? and (ii) what are the weak points of the DSM and ICD classifications?

One hundred years of progress in the study of interstitial nephritis has expanded our diagnostic entities, resulted in identification of numerous pathogenic events, and defined the nature of the inflammatory infiltrate in ways that are useful both for general understanding and for diagnostic classification. We stand poised to enter the next hundred years with new techniques applicable to renal biopsies that detect specific biologic activities in situ in tissue sections. In the future, the information gained from these techniques is likely to result in refined and more accurate assessments of prognosis in patients with kidney disease, and to guide therapeutic interventions designed to interrupt specific sequences of active renal injury.

This study examined the level of agreement between raters in the diagnosis of headache using the Ad Hoc Committee (AHC) on the Classification of Headache and the Headache Classification Committee of the International Headache Society (IHS) classification criteria. In addition, differences in classification of headache between the AHC and IHS classification systems were considered. Analyses indicated that both the AHC and IHS classification systems were adequate in allowing clinicians to reach 100% agreement in diagnosis of headache cases (N = 36). Additionally, there was 91.7% diagnostic agreement between the two sets of criteria as applied by the raters. Differences in diagnostic classification between the two sets of criteria were believed to be the result of IHS exclusionary criteria in the classification of Tension-type headache.

The diagnostic utility of objective measures of inattention, impulsivity, and activity level was assessed by examining the classification of ADHD and non-ADHD patients, as well as normal children. Discriminant function analyses correctly classified 72.4% of subjects in the ADHD versus normal control comparison, and 66.2% in the ADHD versus non-ADHD comparison. Poor performance on objective measures was generally indicative of ADHD relative to normal controls, but “average” performance could not be used to rule out ADHD. Diagnostic classification indices were much lower in the ADHD versus non-ADHD patient discrimination. CPT-inattention scores had moderate sensitivity, but low specificity; CPT-impulsivity and actigraph scores had low sensitivity but high specificity. These findings are discussed in terms of the utility of these objective measures for assessing ADHD in clinical and nonclinical populations.

German clinicians began describing individuals with some form of gender discomfort over 160 vears ago. This culminated with the publication of Die Transvestiten by Magnus Hirschfeld in 1910. Currently, the most commonly used terms for these conditions are transsexualism, gender dysphoia, and gender identity disorders (GID). With the publication of the 3rd edition of The Diagnostic and Statistical Manual (DSM-III) of the American Psychiatric Association in 1980, one finds mention of these GID for the first lime in a formal diagnostic classification system. These GID were further legitimized in 1987, with the publication of DSM-III-Revised. Currently, DSM-IV is under preparation by a subcommittee on GID. There is considerable controversy about revisions in terminology and classification of these GID currently under discussion. This paper also deals with the relationship between gender identity and sexual orientation. There is some evidence to suggest a correlation between age of onset of gender dysphoria an...

A controlled study assessed the reliability of retinal nerve fibre layer defects as paraclinical evidence for use in the diagnostic classification of multiple sclerosis (MS). The retinal nerve fibr...

The process of classification is examined in a southern U.S. prison system. Staff directly involved in classification activities in the seven prisons for males, one prison for females and the diagnostic center reported on their classification activities. Factors thought by staff to be important in classifying an offender, use of the diagnostic classification summary, and staff knowledge of the capabilities of other institutions in the system were examined. Staff perceptions of the importance and accuracy of different sources of information and the discrepancy between the two at initial classification and reclassification were used to develop hypotheses regarding possible changes to facilitate the classification process.

(1995). Diagnostic Classification Task Force (1994). Diagnostic Classification: 0–3, Diagnostic Classification of Mental Health and Developmental Disorders of Infancy and Early Childhood.. TCA Journal: Vol. 23, No. 1, pp. 68-69.

From its first clear description in the late 17th century, the concept of anorexia nervosa has undergone numerous descriptive and ideologic changes, culminating in the present diagnostic classification which includes weight loss, disturbed body image, fear of obesity and refusal to maintain body weight in the absence of physical illness. Numerous associated clinical features are described, thereby aiding the assessment of the magnitude of the disorder and the development of an integrated treatment program. A differential diagnosis is presented.

Twenty five male and 25 female heterosexual patients and their partners presenting with sexual dysfunction at a Psychosexual Clinic were assessed, before treatment, using a questionnaire measure of Sexual Interest, (Quinn et at, 1974). The relationship of the diagnostic classification of patients was examined. It was found that the difference in total sexual interest between the patients and partner discriminated between sexual dysfunctions, as categorised in this investigation. This tendency was more marked with male sexual dysfunction than female.

A nationwide study has been carried out linking the National Birth Register and the National Psychiatric Register, using the identification of the mother as linkage. The study comprises all women who during the period from 1 January 1973 to 31 December 1983 gave birth to a child, and who during a period from 2 years before to 2 years after the childbirth were admitted to a Danish psychiatric institution. All information from both registers is included in the study. The material consists of 6671 women having 10,291 childbirths and 26,235 psychiatric admissions. The methodologic problems relating to delineation of study interval, diagnostic classification, choice of diagnosis, psychosocial factors, and mother-child relationship are discussed.

A retrospective analysis of the case records of 60 pupils at a Speech and Language Unit was used to examine the predictive power of a diagnostic classification system based on deviance and delay. In addition to showing that neither early age of admission nor long duration of stay were associated with favourable outcomes, and that girls were more likely than boys to suffer from additional handicaps, the study identified three major assessment dimensions and linked diagnostic category with both severity of disorder and response to the treatment programme.

Guidance officers who received referral information in which a child's sex, age, reason for referral, attainment and IQ levels were systematically varied, were asked to indicate the likelihood that the child was emotionally disturbed (ED), learning disabled (LD), mildly intellectually handicapped (MIH), or perceptually‐motor impaired (PMI). There was inconsistency in their identification of children as ED, LD and PMI; most cases were classified as MIH with IQ as the main influencing factor. The least exceptional children were the most likely to be categorized as PMI.

Using the DIS, we examined DSM-III alcoholism criteria and final diagnostic classification in a sample of youths and adults who were about to begin inpatient treatment for alcohol and/or substance abuse. We found differences between adults and youths in the percentage of subjects endorsing several of the criterion indicators used to derive the DSM-III alcoholism diagnosis. For the most part, a larger percentage of adults had experienced alcohol-related disturbances, but the high levels of item endorsement among the youths surprised us. On the average, youths endorsed fewer DSM-III crieterion items than did adults, and the incidence of alcohol dependency, as measured by diagnostic classification, was lower for youths than for adults. Overall, 76% of youths were diagnosed as either alcohol abusing or alcohol dependent, as compared to 86% of adults who were so diagnosed. We speculate that the figures for both groups would have been even higher had the sample been restricted to individuals seeking treatment f...

This paper offers a working diagnostic classification scheme that is intended for use at the first clinical appointment for patients with TM disorders. It does not differentiate between muscle-induced and nonmuscle-induced disk interference disorders. This study was designed to measure the occurrence of specific diagnoses in one clinical practice, delineate what to expect from conservative management, and analyze resultant data to determine the predominance of any malocclusion types in the development of TM disorder symptoms. The sample comprised 295 patients, producing 351 specific diagnoses.

Neurobehavioral evaluation of the high-risk neonate represents an important advance in early detection of behavioral anomalies which may give rise to later neuropsychological sequelae. In the present study neonates comprising three diagnostic categories (i.e., respiratory distressed, seizure-disordered, normals) were evaluated with the Brazelton Neonatal Behavior Assessment Scale (BNBAS) to determine the extent to which differences in neurobehavioral organization could be detected with the scale, and how they were related to diagnostic classification. Average conceptional age at testing for the three groups was within the range usually considered full term: e.g., 38.81 weeks (respiratory distressed), 40.18 weeks (normal healthy) and 42.54 weeks (seizure disorder). Infants who had been diagnosed with neonatal seizures exhibited consistently less optimal behavior than did either of the other two groups. Infants with respiratory distress and normal controls did not differ significantly on most summary measures of neurobehavioral organization scored with the BNBAS. The study offers support for the discriminative validity of the BNBAS and its potential usefulness in the assessment of clinically ill newborns.

Three pedigrees were selected from the literature for their compatibility with the hypothesis of linkage between the X‐chromosome marker color blindness and bipolar affective disorder. We compared the results of linkage analyses of these pedigrees when both penetrance function and diagnostic classification were varied. The analyses show that the incorporation of age‐of‐onset information into a penetrance function significantly increased the evidence for linkage. In addition, assumptions about diagnostic classification affected the lod scores. These results demonstrate the need for careful consideration of diagnostic criteria and variable age‐of‐onset when pursuing linkage analysis of complex traits.

This paper describes the use of the "delegate scoring" system of Sandler in combination with the diagonal method of factor analysis and presents the rationale for its application in G analysis. Using selected empirical data for a demonstration study, the system was applied to the test score responses of 17 schizophrenic persons. Three Q factors representing regressive, latent, and paranoid schizophrenics were obtained.