Diagnostic accuracy and confusability analyses: an application to the Diagnostic Interview for Genetic Studies

Concurrent validation of schizotaxia: a pilot study

BACKGROUND

Many first-degree relatives of patients with schizophrenia show deficits in clinical, neuropsychological, neurobiological and social domains, in the absence of psychosis. We recently reformulated Meehl's concept of schizotaxia to conceptualize the liability to schizophrenia, and we proposed preliminary criteria based on the presence of negative symptoms and neuropsychological deficits. Here we investigate the concurrent validity of schizotaxia by comparing a group of subjects who met criteria for schizotaxia with a group who did not on independent measures of clinical function, and on lifetime rates of selected comorbid psychiatric disorders.

METHODS

Twenty-seven adults who were first-degree, biological relatives of patients with schizophrenia were evaluated for schizotaxia based on our predetermined criteria involving negative symptoms and neuropsychological deficits. Subjects also received portions of the Diagnostic Interview for Genetic Studies, the Structured Interview for Schizotypy, the Family Interview for Genetic Studies, the DSM-IV Global Assessment of Functioning, the Physical Anhedonia Scale, the Social Adjustment Scale and the Symptom Checklist-90-Revised. Subjects who met criteria for schizotaxia were compared with those who did not on each of the clinical measures, and on their rates of comorbid DSM-IV psychiatric diagnoses.

RESULTS

Eight subjects met criteria for schizotaxia, and 19 did not. Subjects with schizotaxia showed significantly lower levels of function on each of the clinical scales. Differences in comorbid psychiatric diagnoses were not significant, although the rate of lifetime substance abuse diagnoses in the schizotaxic group (50%) approached levels that are often seen in schizophrenia.

CONCLUSIONS

These findings provide the first evidence of concurrent validation for a proposed syndrome of schizotaxia. They are also consistent with the view that the vulnerability to schizophrenia may be defined, at least partially, although larger studies to assess both the concurrent and predictive validity of schizotaxia will be required to confirm these results.

Multicenter linkage study of schizophrenia candidate regions on chromosomes 5q, 6q, 10p, and 13q: schizophrenia linkage collaborative group III

Schizophrenia candidate regions 33-51 cM in length on chromosomes 5q, 6q, 10p, and 13q were investigated for genetic linkage with mapped markers with an average spacing of 5.64 cM. We studied 734 informative multiplex pedigrees (824 independent affected sibling pairs [ASPs], or 1,003 ASPs when all possible pairs are counted), which were collected in eight centers. Cases with diagnoses of schizophrenia or schizoaffective disorder (DSM-IIIR criteria) were considered affected (n=1,937). Data were analyzed with multipoint methods, including nonparametric linkage (NPL), ASP analysis using the possible-triangle method, and logistic-regression analysis of identity-by-descent (IBD) sharing in ASPs with sample as a covariate, in a test for intersample heterogeneity and for linkage with allowance for intersample heterogeneity. The data most supportive for linkage to schizophrenia were from chromosome 6q; logistic-regression analysis of linkage allowing for intersample heterogeneity produced an empirical P value <.0002 with, or P=.0004 without, inclusion of the sample that produced the first positive report in this region; the maximum NPL score in this region was 2.47 (P=.0046), the maximum LOD score (MLS) from ASP analysis was 3.10 (empirical P=.0036), and there was significant evidence for intersample heterogeneity (empirical P=.0038). More-modest support for linkage was observed for chromosome 10p, with logistic-regression analysis of linkage producing an empirical P=. 045 and with significant evidence for intersample heterogeneity (empirical P=.0096).

Department of Veterans Affairs Cooperative Studies Program genetic linkage study of schizophrenia: ascertainment methods and sample description

To help clarify the genetics of schizophrenia, the Department of Veterans Affairs Cooperative Studies Program has completed data collection for a genetic linkage study of schizophrenia. This article describes the methodological details of the data collection. Subsequent articles will describe the results of our genome scan, which is now in progress. The data collection protocol included the Diagnostic Interview for Genetic Studies, the Family Interview for Genetic Studies, a review of medical records, and the collection of blood for transformation into lymphoblast cell lines. Among relatives of schizophrenic probands, we assessed auditory attention and verbal memory with neuropsychological tests. Among the 166 families ascertained for the study, 143 had a single affected sib-pair, 17 had three affected siblings, one had five affected siblings and five had two sets of affected siblings. There was a total of 216 affected sib-pairs in these families. Using the n-1 rule, these families contain 188 independent affected sib-pairs.

Estimation of sensitivity and specificity of diagnostic tests and disease prevalence when the true disease state is unknown

The performance of a new diagnostic test is frequently evaluated by comparison to a perfect reference test (i.e. a gold standard). In many instances, however, a reference test is less than perfect. In this paper, we review methods for estimation of the accuracy of a diagnostic test when an imperfect reference test with known classification errors is available. Furthermore, we focus our presentation on available methods of estimation of test characteristics when the sensitivity and specificity of both tests are unknown. We present some of the available statistical methods for estimation of the accuracy of diagnostic tests when a reference test does not exist (including maximum likelihood estimation and Bayesian inference). We illustrate the application of the described methods using data from an evaluation of a nested polymerase chain reaction and microscopic examination of kidney imprints for detection of Nucleospora salmonis in rainbow trout.

Treatment of schizoaffective disorder and schizophrenia with mood symptoms

OBJECTIVE

Patients with concurrent schizophrenic and mood symptoms are often treated with antipsychotics plus antidepressant or thymoleptic drugs. The authors review the literature on treatment of two overlapping groups of patients: those with schizoaffective disorder and those with schizophrenia and concurrent mood symptoms.

METHOD

MEDLINE searches (from 1976 onward) were undertaken to identify treatment studies of both groups, and references in these reports were checked. Selection of studies for review was based on the use of specified diagnostic criteria and of parallel-group, double-blind design (or, where few such studies addressed a particular issue, large open studies). A total of 18 treatment studies of schizoaffective disorder and 15 of schizophrenia with mood symptoms were selected for review.

RESULTS

For acute exacerbations of schizoaffective disorder or of schizophrenia with mood symptoms, antipsychotics appeared to be as effective as combination treatments, and there was some evidence for superior efficacy of atypical antipsychotics. There was evidence supporting adjunctive antidepressant treatment for schizophrenic and schizoaffective patients who develop a major depressive syndrome after remission of acute psychosis, but there were mixed results for treatment of subsyndromal depression. There was little evidence to support adjunctive lithium for depressive symptoms and no evidence concerning its use for manic symptoms in patients with schizophrenia.

CONCLUSIONS

Empirical data suggest that both groups of patients are best treated by optimizing antipsychotic treatment and that atypical antipsychotics may prove to be most effective. Adjunctive antidepressants may be useful for patients with major depression who are not acutely ill. Careful longitudinal assessment is required to ensure identification of primary mood disorders.