Evaluation of Rules for Coping with Insufficient Data in Constraint-Based Search Algorithms

A fundamental step in the PC causal discovery algorithm consists of testing for (conditional) independence. When the number of data records is very small, a classical statistical independence test is typically unable to reject the (null) independence hypothesis. In this paper, we are comparing two conflicting pieces of advice in the literature that in case of too few data records recommend (1) assuming dependence and (2) assuming independence. Our results show that assuming independence is a safer strategy in minimizing the structural distance between the causal structure that has generated the data and the discovered structure. We also propose a simple improvement on the PC algorithm that we call blacklisting. We demonstrate that blacklisting can lead to orders of magnitude savings in computation by avoiding unnecessary independence tests

Genetic Studies of Autistic Disorder and Chromosome 7

Genome-wide scans have suggested that a locus on 7q is involved in the etiology of autistic disorder (AD). We have identified an AD family in which three sibs inherited from their mother a paracentric inversion in the chromosome 7 candidate region (inv(7)(q22–q31.2)). Clinically, the two male sibs have AD, while the female sib has expressive language disorder. The mother carries the inversion, but does not express AD. Haplotype data on the family suggest that the chromosomal origin of the inversion was from the children's maternal grandfather. Based on these data, we have genotyped 76 multiplex (≥2 AD affecteds/family) families for markers in this region of 7q. Two-point linkage analysis yielded a maximum heterogeneity lod score of 1.47 and maximum lod score (MLS) of 1.03 at D7S495. Multipoint MLS and NPL analyses resulted in peak scores of 1.77 at D7S2527 and 2.01 at D7S640. Examination of affected sibpairs revealed significant paternal (P = 0.007), but not maternal (P = 0.75), identity-by-descent sharing at D7S640. Significant linkage disequilibrium was detected with paternal (P = 0.02), but not maternal (P = 0.15), transmissions at D7S1824 in multiplex and singleton families. There was also evidence for an increase in recombination in the region (D7S1817 to D7S1824) in the AD families versus non-AD families (P = 0.03, sex-averaged; and P = 0.01, sex-specific). These results provide further evidence for the presence of an AD locus on chromosome 7q, as well as provide evidence suggesting that this locus may be paternally expressed

Public health medicine and primary health care: convergent, divergent, or parallel paths?

Historically, general medical practitioners and public health doctors have striven for health goals by different means. General practice has concentrated on personal, continuing health care focused on the consultation, usually at the request of the patient. Public health doctors have emphasised changes in the environment, society, and health service provision and organisation as the basis of interventions impacting on whole populations, or on marginalised groups of the population. Changes in medical practice, social and health care organisation, and political and public expectation have forced a radical reappraisal of the traditional relationship between these two branches of medical practice. These changes include the incorporation within general practice of staff such as health visitors and district nurses spurring on the concept of primary health care; the deliberate and successful shift, continuing to gather momentum, towards preventive health care in general practice; and the move towards greater administrative involvement of general practitioners in the management, organisation, and development of health services, hastened by the NHS reforms and best exemplified by fund holding general practices. The increasing focus of public health medicine on the assessment of health and health care needs, the development of policy and strategy, the promotion of health, the control and prevention of disease, and the organisation of services (activities undertaken at the expense, in practice if not in principle, of the control of environmental hazards and the advocacy role) has coincided with these changes in general practice. In the UK the fusion of the district and family health services authorities, and the increasing involvement of general practitioners in commissioning, and the requirement of health authority staff to support general practice commissioners make a strong relationship between the two medial specialties essential. In what direction has the relationship been moving