The weighted rank pairwise correlation statistic for linkage analysis: Simulation study and application to Alzheimer's disease

The weighted rank pairwise correlation (WRPC) statistic has been proposed as a robust test of genetic linkage, particularly adapted to the analysis of large and complex pedigrees and for age-dependent and heterogeneous diseases. In this paper a simulation study is presented. Validity and power of the WRPC test are studied and compared to the Haseman-Elston sibpair method for various types of problems. The power of the WRPC test is slightly lower than the Haseman-Elston method for analyzing a large number of small randomly chosen pedigrees. It is higher however in presence of genetic heterogeneity or for analyzing large individual pedigrees. Recently, evidence of linkage of Alzheimer's disease with a locus on chromosome 14, D14s43, has been obtained by the Lod-score method. We reanalyze these data using the WRPC test, essentially confirming the results of the Lod-score method. The WRPC test statistic is higher than the equivalent Lod-score statistic for the two pedigrees which show strong evidence of linkage with the two methods. The global WRPC test statistic is slightly lower than the Lod-score test statistic. The WRPC test, however, makes no hypothesis of a specific genetic transmission model and can be computed very quickly; in addition, an exact P-value can be computed by simulation for individual pedigrees. © 1994 Wiley-Liss, Inc.     

The structure of wandering in dementia

‘Wandering’ is one of the most troublesome of behavioural problems in dementia. The term ‘wandering’ covers many different types of behaviour. We examined the hypothesis that the different types of wandering behaviour seen in dementia from a scale using data collected on 83 elderly subjects suffering from either Alzheimer's disease or multiinfarct dementia. We reject the scaling hypothesis. Our data suggest that there are three main categories of wandering behaviour, and that one of these categories is usefully divided into four subcategories.     

Immunohistochemical characterization of cellular infiltrates in squamous cell carcinoma and Bowen's disease occurring in one patient.

We investigated populations of the infiltrating cells in Bowen's disease (BD) and squamous cell carcinoma (SCC), both of which arose in the same patient, using the Avidin-Biotin-peroxidase complex method with eight monoclonal antibodies. T lymphocytes were most predominant among infiltrating cells; NK cells, B cells, and monocytes were rarely seen in either BD or SCC. Analysis of subsets of the infiltrating T lymphocytes revealed that the number of suppressor/cytotoxic (s/c) T cells was twice that of helper/inducer (h/i) T cells in BD, while the number of s/c T cells was lower than that of h/i T cells in SCC. The immunohistochemical results in the present case differed from those of predominant infiltration of h/i T cells and of s/c T cells in three other reports of BD and SCC. These results suggest that the population of the cellular infiltrates may be modulated by the nature of tumors and by the immuno-competent state of the hosts.     

Altered corticomotor representation in patients with Parkinson's disease.

In 6 patients with Parkinson's disease (PD) and 6 age-matched controls, transcranial magnetic stimulation was applied at 56 regions over the motor cortex and premotor cortex of each hemisphere, with the first dorsal interosseous (FDI) muscle of both hands activated at 15% maximum voluntary contraction during stimulation. For each site, motor evoked potential (MEP) landmarks were recovered, including MEP amplitude, MEP onset latency, and silent period duration. Scaled MEP amplitudes were used to construct individual cortical maps of the FDI muscles. The maps revealed an anterior displacement of the muscle representation in PD patients. This anterior shift over motor cortical areas may reflect increased contributions of corticocortical connections between motor cortex and premotor cortical areas, possibly enhanced by the visual feedback aspect of the task. These alterations may reflect adaptations to the impairments in striatocortical circuits in PD.     

Development of quality of care indicators for Parkinson's disease.

Parkinson's disease (PD) is a major cause of disability. To date, there have been no large-scale efforts to measure the quality of PD care because of a lack of quality indicators for conducting an explicit review of PD care processes. We present a set of quality indicators for PD care. Based on a structured review of the medical literature, 79 potential indicators were drafted. Through a two-round modified Delphi process, an expert panel of seven movement disorders specialists rated each indicator on criteria of validity, feasibility, impact on outcomes, room for improvement, and overall utility. Seventy-one quality indicators met validity and feasibility thresholds. Applying thresholds for impact on outcomes, room for improvement, and overall utility, a subset of 29 indicators was identified, spanning dopaminergic therapy, assessment of functional status, assessment and treatment of depression, coordination of care, and medication use. Multivariable analysis showed that overall utility ratings were driven by validity and impact on outcomes (P < 0.01). An expert panel can reach consensus on a set of highly rated quality indicators for PD care, which can be used to assess quality of PD care and guide the design of quality improvement projects.     

Assessment of autonomic dysfunction in Parkinson's disease: the SCOPA-AUT.

We developed a questionnaire to assess autonomic symptoms in patients with Parkinson's disease (PD) and evaluated its reliability and validity. Based on the results of a postal survey in 46 PD patients, 21 multiple system atrophy patients, and 8 movement disorders specialists, items were included according to their frequency, burden, and clinical relevance. The questionnaire was evaluated in 140 PD patients and 100 controls, and test-retest reliability was established in a sample of 55 PD patients. The SCOPA-AUT consists of 25 items assessing the following regions: gastrointestinal (7), urinary (6), cardiovascular (3), thermoregulatory (4), pupillomotor (1), and sexual (2 items for men and 2 items for women) dysfunction. Test-retest reliability was good. Autonomic problems increased significantly with increasing disease severity for all autonomic regions, except sexual dysfunction. We conclude that SCOPA-AUT is a reliable and valid questionnaire that evaluates autonomic dysfunction in PD.     

Depression symptoms in movement disorders: comparing Parkinson's disease, dystonia, and essential tremor.

Depression is common in Parkinson's disease (PD) and affects 30 to 50% of all patients. In contrast to the wealth of research on depression in PD, little is known about the occurrence of depression in other movement disorders. The primary objective of the current study was to determine whether the high prevalence of depression symptoms seen in PD is also found in other movement disorders, by directly comparing rates of specific depression symptoms and depression severity across PD, dystonia, and essential tremor (ET). Three hundred and fifty-four patients with PD, 83 patients with dystonia, and 53 patients with ET completed the Beck Depression Inventory (BDI). We found no significant between-groups differences for depression severity, frequency, or endorsement of specific depression symptoms. Forty-eight percent of PD patients, 37.3% of dystonia patients, and 34% of ET patients were found to be at least mildly depressed (BDI score of 10 or higher). The most commonly endorsed symptoms were fatigability, difficulty with work, anhedonia, and sleep disturbance. Clinicians should be aware that depression is a frequent problem in dystonia and ET, in addition to PD, and inquire about depression symptoms in these patients so that they can be appropriately treated.     

Inter-rater reliability of the International Cooperative Ataxia Rating Scale (ICARS).

We assessed the inter-rater reliability of the 100-point International Cooperative Ataxia Rating Scale (ICARS). Three neurologists independently rated videotaped ICARS examinations of 22 subjects with genetically determined ataxias (spinocerebellar ataxia [SCA] Type 1 in 11; SCA Type 2 in 1; Friedreich's ataxia in 10) and 4 controls. Scores on live ICARS assessment had ranged from 0 to 7 for controls and 11 to 74 for ataxic subjects (clinically very mildly affected to wheelchair-bound). Inter-rater correlation was very high for the total score (Kendall's omega 0.994, 95% confidence interval, 0.988-0.997), and high to very high for each component subscore (0.791 for speech to 0.994 for posture/gait). All correlations were significant at P < 0.00001. The ICARS exhibits very high inter-rater reliability even without prior observer standardisation and is sensitive to a range of ataxia severities from very mild to severe.     

Proteasome inhibitor model of Parkinson's disease in mice is confounded by neurotoxicity of the ethanol vehicle.

Defects in the ubiquitin-proteasome system have been implicated in Parkinson's Disease (PD). Recently, a rat model of PD was developed using a synthetic proteasome inhibitor (PSI), (Z-lle-Glu(OtBu)-Ala-Leu-al). We attempted to transfer this model to mouse studies, where genetics can be more readily investigated due to the availability of genetically modified mice. We treated C57BL/6 (B6) mice with six intraperitoneal injections of 6 mg/kg PSI in 50 mul of 70% ethanol over a 2-week-period. We found significant decreases in nigrostriatal dopamine in PSI-treated mice compared with saline-treated mice. However, we observed similar decreases in the ethanol-treated vehicle control group. Administration of ethanol alone led to significant long-term alterations in dopamine levels. Ethanol significantly eclipses the effects of PSI in the dopamine system, and therefore is a confounding vehicle for this model.     

Identifying incident cases of parkinsonism among veterans using a tertiary medical center.

To better understand the impact of incident Parkinson's disease (PD) on the Veteran's Health Administration (VHA) and to develop methods applicable to future epidemiological research, we performed a medical record review study at a tertiary referral VHA medical center. Searching the local data base, we identified 782 veterans with diagnostic codes for PD or secondary parkinsonism (SP) between 1998 and 2000. Based on structured medical record review, a movement disorders specialist confirmed diagnoses for incident parkinsonism cases. Among the 782, 191 incident parkinsonism cases were identified (100 PD, 75 SP, and 16 Parkinson's Plus). Incident PD cases were older at diagnosis (74.5 vs. 70.4 yr; P < 0.05) and more likely to be white (81% vs. 62; P < 0.07) than incident SP cases. Diagnostic codes were insufficient to distinguish between incident PD and SP (positive predictive value, 57% and 39%, respectively), and VHA sources failed to identify 21% of confirmed deaths among the incident PD cohort by November 2004. Although the large number of incident cases identified suggests PD is an important cause of disability among elderly VHA users, observed limitations of VHA sources for identifying incident PD cases and determining their vital status should be considered when designing future studies.