Christopher Snell

Source:Workwell

Christopher R. Snell, PhD, is the Scientific Director of Workwell Foundation, Ripon, California. Dr. Snell was Chair of the Health and Human Services's CFSAC committee from 04/01/07-04/01/11.

Open Letter to The Lancet

Two open letters to the editor of The Lancet urged the editor to commission a fully independent review of the PACE trial, which the journal had published in 2011. In 2016, Dr. Snell, along with 41 colleagues in the ME/CFS field, signed the second letter.

• 10 February 2016, An open letter to The Lancet, again - Virology blog

Notable studies

• 2012, Minimum data elements for research reports on CFS. Full text

  Abstract: "Chronic fatigue syndrome (CFS) is a debilitating condition that has received increasing attention from researchers in the past decade. However, it has become difficult to compare data collected in different laboratories due to the variability in basic information regarding descriptions of sampling methods, patient characteristics, and clinical assessments. The issue of variability in CFS research was recently highlighted at the NIH's 2011 State of the Knowledge of CFS meeting prompting researchers to consider the critical information that should be included in CFS research reports. To address this problem, we present our consensus on the minimum data elements that should be included in all CFS research reports, along with additional elements that are currently being evaluated in specific research studies that show promise as important patient descriptors for subgrouping of CFS. These recommendations are intended to improve the consistency of reported methods and the interpretability of reported results. Adherence to minimum standards and increased reporting consistency will allow for better comparisons among published CFS articles, provide guidance for future research and foster the generation of knowledge that can directly benefit the patient."

• 2010, Post-exertional malaise in women with chronic fatigue syndrome
• 2007, Legal and Scientific Considerations of the Exercise Stress Test

  "Abstract - This article examines the legal and scientific bases on which an exercise stress test can provide medically acceptable evidence of disability for the Chronic Fatigue Syndrome (CFS) patient. To qualify for disability benefits, a claimant must establish the existence of a serious medically determinable impairment (MDI) that causes the inability to work. The single stress test has been used to objectively establish whether a claimant can engage in “substantial gainful employment” and is an important determinant of the award or denial of benefits. A review of case law indicates problems associated with a single test protocol that may be remedied by a “test-retest” protocol. The results of a preliminary study employing this approach indicate that the test-retest protocol addresses problems inherent in a single test and therefore provides an assessment of CFS related disability consistent with both medical and legal considerations."

• 2007, Diminished Cardiopulmonary Capacity During Post-Exertional Malaise

  "Abstract - Reduced functional capacity and post-exertional malaise following physical activity are hallmark symptoms of Chronic Fatigue Syndrome (CFS). That these symptoms are often delayed may explain the equivocal results for clinical cardiopulmonary exercise testing with CFS patients. The reproducibility of VO2 max in healthy subjects is well documented. This may not be the case with CFS due to delayed recovery symptoms. Purpose: To compare results from repeated exercise tests as indicators of post-exertional malaise in CFS. Methods: Peak oxygen consumption (VO2 peak), percentage of predicted peak heart rate (HR%), and VO2 at anaerobic threshold (AT), were compared between six CFS patients and six control subjects for two maximal exercise tests separated by 24 hours. Results: Multivariate analysis showed no significant differences between control and CFS, respectively, for test 1: VO2 peak (28.4 ± 7.2 ml/ kg/min; 26.2 ± 4.9 ml/kg/min), AT (17.5 ± 4.8 ml/kg/min; 15.0 ± 4.9 ml/ kg/min) or HR% (87.0 ± 25.4%; 94.8 ± 8.8%). However, for test 2 the CFS patients achieved significantly lower values for both VO2 peak (28.9 ± 8.0 ml/kg/min; 20.5 ± 1.8 ml/kg/min, p = 0.031) and AT (18.0 ± 5.2 ml/kg/min; 11.0 ± 3.4 ml/kg/min, p = 0.021). HR% was not significantly different (97.6 ± 27.2%; 87.8 ± 9.3%, p = 0.07). A follow-up classification analysis differentiated between CFS patients and controls with an overall accuracy of 92%. Conclusion: In the absence of a second exercise test, the lack of any significant differences for the first test would appear to suggest no functional impairment in CFS patients. However, the results from the second test indicate the presence of a CFS related post-exertional malaise. It might be concluded then that a single exercise test is insufficient to demonstrate functional impairment in CFS patients. A second test may be necessary to document the atypical recovery response and protracted malaise unique to CFS."

• 2004, Immunologic Aspects of Chronic Fatigue Syndrome: Report on a Research Symposium Convened by The CFIDS Association of America and Co-Sponsored by the US Centers for Disease Control and Prevention and the National Institutes of Health

  "Abstract - Chronic fatigue syndrome (CFS) is a serious health concern affecting over 800,000 Americans of all ages, races, socioeconomic groups and genders. The etiology and pathophysiology of CFS are unknown, yet studies have suggested an involvement of the immune system. A symposium was organized in October 2001 to explore the possibility of an association between immune dysfunction and CFS, with special emphasis on the interactions between immune dysfunction and other abnormalities noted in the neuroendocrine and autonomic nervous systems of individuals with CFS. This paper represents the consensus of the panel of experts who participated in this meeting. Data suggest that persons with CFS manifest changes in immune responses that fall outside normative ranges, but current research does not provide definitive evidence on whether these immune abnormalities are a cause or result of the illness. It has become clear that CFS cannot be understood based on single measurements of immune, endocrine, cardiovascular, or autonomic nervous system dysfunction. This panel encourages a new emphasis on multidisciplinary research into CFS."

• 2001, Assessment of Functional Impairment by Cardiopulmonary Exercise Testing in Patients with Chronic Fatigue Syndrome

  "Summary - Functional impairment in a population of patients with chronic fatigue syndrome (CFS) was determined by exercise testing. The criteria established by Weber and Janicki (1) were employed because impairment levels are based on maximal oxygen consumption. Oxygen consumption was obtained by cardiopulmonary exercise testing and was used to classify subjects according to the severity of impairment. All the subjects in this study met the CDC case definition (2) for CFS. All patients underwent at least two maximal graded exercise tests in which expired air was collected for assessment of V02max. Data are included for eighty-seven CFS patients, the highest V02 was used for determining impairment. Although all patients met the CDC case definition for CFS, only 35 (40%) would be classified as having greater than “Mild” functional impairment. The highest V02 of any of the patients in this study was 29.5 ml/kg/min, very close to what normative data predicts to be the average maximal value for the entire group. Without a sedentary control group it is unclear if the low V02 in this population is due to the pathology of CFS or results from the inactivity that accompanies the disease. However, use of maximal V02 during exercise can clearly discriminate between levels of functional impairment and may be efficacious for diagnosis of CFS. Additionally, in cases where cardiopulmonary analysis is unavailable, exercise duration on a standardized test may also be employed."

• 2001, Chronic Fatigue Syndrome, Ampligen, and Quality of Life: A Phenomenological Perspective

  "Summary - The purpose of this investigation was to identify significant quality-of-life issues for two women previously diagnosed with chronic fatigue syndrome (CFS), and their families. Both women were participants in a cost-recovery, clinical trial of the antiviral and immuno-modulatory drug, Ampligen. A qualitative, case study approach was adopted to access information not normally available from clinical trials. Specifically, semi-structured, in-depth interviews were conducted with the CFS patients, and their spouses, to discover if these families perceived any changes in their patterns of daily living contingent with participation in the Ampligen trial. Patient diaries were also analyzed for the purpose of triangulation. Content analysis of the interview transcripts and diary entries revealed a number of significant quality of life improvements for the women and their families, for which they perceived the drug therapy responsible. After an initial acclimation period, and with the exception of the day when the drug was administered, both women reported a reduction in pain, increased energy levels, and improved cognitive functioning. They each cited numerous cases to illustrate their improvement."

Talks and interviews

• 2016, 12th International IACFS/ME Biennial Clinical and Research Conference, Emerging Science and Clinical Care, How Cardiopulmonary Exercise Testing Informs Pathology and Treatment(Workshop given with Mark VanNess, Ph.D. and Betsy Keller, Ph.D.)
• 2012,

Learn more

• 2012, Clinical exercise testing in CFS/ME research and treatment

See Also

• Staci Stevens
• Workwell Foundation
• Two-day cardiopulmonary exercise testing
• Exercise
• Mark VanNess

National Institutes of Health (NIH) - A set of biomedical research institutes operated by the U.S. government, under the auspices of the Department of Health and Human Services.

stress Stress can by either physical or psychological, or both. Stress is either 1) a state of emotional or psychological strain or 2) the physical stress (pressure or tension) that a physical object such the human body is placed under, e.g., a stress test is a medical test that monitors the cardiovascular system during strenuous exercise.

post-exertional malaise (PEM) - A notable exacerbation of symptoms brought on by small physical or cognitive exertions. PEM may be referred to as a "crash" or "collapse" and can last for days or weeks. Symptoms can include cognitive impairments, muscle pain, trouble remaining upright (orthostatic intolerance), sleep abnormalities, and gastro-intestinal impairments, and others.

VO2 Max (VO2max) - the maximum amount of oxygen the body can utilize during a specified period of usually intense exercise (Volume of O2 Maximal)

heart rate (HR) - the number of times the heart beats within a certain time period, usually a minute

heart rate (HR) - the number of times the heart beats within a certain time period, usually a minute

accuracy The "closeness of an observation to the true clinical state". With respect to diagnostic tests, "accuracy" means how specific and sensitive the test is.

etiology The cause of origin, especially of a disease.

neuroendocrine relating to hormones that influence the nervous system

VO2 Max (VO2max) - the maximum amount of oxygen the body can utilize during a specified period of usually intense exercise (Volume of O2 Maximal)

Centers for Disease Control and Prevention (CDC) - The Centers for Disease Control and Prevention is a U.S. government agency dedicated to epidemiology and public health. It operates under the auspices of the Department of Health and Human Services.

cognition Thought processes, including attention, reasoning, and memory.

Chronic Fatigue and Immune Dysfunction Syndrome (CFIDS) - Chronic Fatigue and Immune Dysfunction Syndrome is another term for Chronic Fatigue Syndrome, but one which emphasizes the immunological aspects of the disease. Popular in the 1990s, this term has apparently fallen into disuse.

Centers for Disease Control and Prevention (CDC) - The Centers for Disease Control and Prevention is a U.S. government agency dedicated to epidemiology and public health. It operates under the auspices of the Department of Health and Human Services.