Problem statement: Several investigators have indicated that case definitions for Chronic Fatigue Syndrome (CFS) are characterized by vaguely worded criteria that lack operational definitions and guidelines. The most widely used CFS case definition is the Fukuda et al. criteria, which uses polythetic criteria (i.e., patients are only required to have four out of a possible eight symptoms). Yet two of these eight symptoms (post-exertional malaise and memory/concentration problems) are an essential feature of this illness and the Fukuda et al. criteria do not require that these symptoms be present among all patients. Significant methodological problems could occur if investigators in different settings recruit samples with different percentages of these core symptoms. In contrast, the Canadian clinical case definition does require specific ME/CFS symptoms such as post-exertional malaise and memory/concentration problems. The provision of operationally explicit, objective criteria on specific key symptoms might reduce criterion variance as a source of unreliability. In addition, the use of structured interview schedules will ensure that symptoms are assessed in a consistent way across settings. Conclusion/Recommendations: In this article, we specified explicit rules for determining whether critical symptoms meet ME/CFS criteria using a revised Canadian case definition and a questionnaire has been developed to assess core symptoms. It is hoped that these developments will lead to increased reliability of this revised Canadian case definition as well as more frequent use of these criteria by investigators.

Helicobacter pylori is a gram-negative bacterium, which colonizes the gastric mucosa of humans and is implicated in a wide range of gastroduodenal diseases. The genomic sequences of two H.pylori strains, 26695 and J99, have been published recently. About two dozen potential restrictionmodification (R-M) systems have been annotated in both genomes, which is far above the average number of R-M systems in other sequenced genomes. Here we describe a functional analysis of the 16 putative Type II R-M systems in the H.pylori J99 genome. To express potentially toxic endonuclease genes, a unique vector was constructed, which features repression and antisense transcription as dual control elements. To determine the methylation activities of putative DNA methyltransferases, we developed polyclonal antibodies able to detect DNA containing N6-methyladenine or N4-methylcytosine. We found that <30% of the potential Type II R-M systems in H.pylori J99 strain were fully functional, displaying both endonuclease and methyltransferase activities. Helicobacter pylori may maintain a variety of functional R-M systems, which are believed to be a primitive bacterial 'immune' system, by alternatively turning on/off a subset of numerous R-M systems.

Aid in understanding issues surrounding the construct validity of fatigue including the distinction between pathological versus nonpathological fatigue. Fatigue is a universal symptom reported by individuals in the general population as well as by those suffering from different medical and psychological illnesses, including cancer, multiple sclerosis, chronic fatigue syndrome, depression, and anxiety. Chronic fatigue is a significant problem in many primary care settings, and the debilitating and prolonged nature of fatigue can pose significant economic consequences for society. Researchers have struggled to better assess and understand the etiology and classification of fatigue within different illness groups.

Objective To review and synthesize findings across qualitative studies on Myalgic Encephalomyelitis/chronic fatigue syndrome (ME/CFS). Methods Articles were systematically reviewed and analyzed within a meta-analytic framework. Analyses included a multi-perspective (e.g., individual, physician, familial) examination of ME/CFS, as well as a comparative analysis of ME/CFS versus other chronic conditions. Results Thirty-four (34) qualitative studies on ME/CFS were identified and included. Findings include three substantive thematic areas that focus on studies concerning: (1) experiences of people with ME/CFS, (2) experiences of physicians, and (3) themes that intersect both of these groups. For patients, illness development influenced identity, reductions in functioning, and coping. Physician-specific themes described lack of awareness about the illness and recommended improvement in medical education. Themes that intersected expressed issues with diagnosis which creates tensions and fuels the stigmatization of ME/CFS. Conclusions Findings indicate multilayered, context-specific experiences and ways in which both people with ME/CFS, as well as the people involved in their lives, such as family or the medical community, understand their illness. Future qualitative studies should coalesce the various facets of the ME/CFS experience, the network members of people with ME/CFS, and the sociocultural environment through which the illness is understood. Practice implications Health care professionals can gain unique insight from patient experiences, allowing for more accurate diagnoses and treatment recommendations.

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