Richard W. McCallum

Bio: Richard W. McCallum is an academic researcher from Texas Tech University Health Sciences Center at El Paso. The author has contributed to research in topics: Gastroparesis & Gastric emptying. The author has an hindex of 81, co-authored 531 publications receiving 22088 citations. Previous affiliations of Richard W. McCallum include University of Virginia & Lynn University.

Demography, clinical characteristics, psychological and abuse profiles, treatment, and long-term follow-up of patients with gastroparesis

Abstract: Patients with gastroparesis frequently present challenging clinical, diagnostic, and therapeutic problems. Data from 146 gastroparesis patients seen over six years were analyzed. Patients were evaluated at the time of initial diagnosis and at the most recent follow-up in terms of gastric emptying and gastrointestinal symptomatology. The psychological status and physical and sexual abuse history in female idiopathic gastroparesis patients were ascertained and an association between those factors and gastrointestinal symptomatology was sought. Eighty-two percent of patients were females (mean age: 45 years old). The mean age for onset of gastroparesis was 33.7 years. The etiologies in 146 patients are: 36% idiopathic, 29% diabetic, 13% postgastric surgery, 7.5% Parkinson's disease, 4.8% collagen vascular disorders, 4.1% intestinal pseudoobstruction, and 6% miscellaneous causes. Subgroups were identified within the idiopathic group: 12 patients (23%) had a presentation consistent with a viral etiology, 48% had very prominent abdominal pain. Other subgroups were gastroesophageal reflux disease and nonulcer dyspepsia (19%), depression (23%), and onset of symptoms immediately after cholecystectomy (8%). Sixty-two percent of women with idiopathic gastroparesis reported a history of physical or sexual abuse, and physical abuse was significantly associated with abdominal pain, somatization, depression, and lifetime surgeries. At the end of the follow-up period, 74% required continuous prokinetic therapy, 22% were able to stop prokinetics, 5% had undergone gastrectomy, 6.2% went onto gastric electrical stimulation (pacing), and 7% had died. At some point 21% had required nutrition support with a feeding jejunostomy tube or periods of parenteral nutrition. A good response to pharmacological agents can be expected in the viral and dyspeptic subgroups of idiopathics, Parkinson's disease, and the majority of diabetics, whereas a poorer outcome to prokinetics can be expected in postgastrectomy patients, those with connective tissue disease, a subgroup of diabetics, and the subset of idiopathic gastroparesis dominated by abdominal pain and history of physical and sexual abuse. Appreciation of the different etiologies and psychological status of the patients may help predict response to prokinetic therapy.

Linking clinical variables with health-related quality of life. A conceptual model of patient outcomes

Abstract: HEALTH-related quality of life (HRQL) is increasingly used as an outcome in clinical trials, effectiveness research, and research on quality of care. Factors that have facilitated this increased usage include the accumulating evidence that measures of HRQL are valid and "reliable,"1the publication of several large clinical trials showing that these outcome measures are responsive to important clinical changes,2-5and the successful development and testing of shorter instruments that are easier to understand and administer.6-13Because these measures describe or characterize what the patient has experienced as the result of medical care, they are useful and important supplements to traditional physiological or biological measures of health status. Given this improved ability to assess patients' health status, how can physicians and health care systems intervene to improve HRQL? Implicit in the use of measures of HRQL in clinical trials and in effectiveness research is the concept that clinical

A standardised static in vitro digestion method suitable for food – an international consensus

Abstract: Simulated gastro-intestinal digestion is widely employed in many fields of food and nutritional sciences, as conducting human trials are often costly, resource intensive, and ethically disputable. As a consequence, in vitro alternatives that determine endpoints such as the bioaccessibility of nutrients and non-nutrients or the digestibility of macronutrients (e.g. lipids, proteins and carbohydrates) are used for screening and building new hypotheses. Various digestion models have been proposed, often impeding the possibility to compare results across research teams. For example, a large variety of enzymes from different sources such as of porcine, rabbit or human origin have been used, differing in their activity and characterization. Differences in pH, mineral type, ionic strength and digestion time, which alter enzyme activity and other phenomena, may also considerably alter results. Other parameters such as the presence of phospholipids, individual enzymes such as gastric lipase and digestive emulsifiers vs. their mixtures (e.g. pancreatin and bile salts), and the ratio of food bolus to digestive fluids, have also been discussed at length. In the present consensus paper, within the COST Infogest network, we propose a general standardised and practical static digestion method based on physiologically relevant conditions that can be applied for various endpoints, which may be amended to accommodate further specific requirements. A frameset of parameters including the oral, gastric and small intestinal digestion are outlined and their relevance discussed in relation to available in vivo data and enzymes. This consensus paper will give a detailed protocol and a line-by-line, guidance, recommendations and justifications but also limitation of the proposed model. This harmonised static, in vitro digestion method for food should aid the production of more comparable data in the future.