Judith Ford (a), Mark Donohoe (b), Derek Behrens (a), Tina McCarthy (a), Phil Thomas (a)
(a)Genetic Consulting & Testing (G C.A. T.) Ply. Ltd.
P.O. Box 210
(b) Environmental & Nutritional Medicine
Is there a Role for Cytogenic Studies in CFS?
Cytogenetic aberrations are one of the most reliable tests for measuring in vitro or in vivo exposure to clastogens (agents, usually chemicals or radiation, which break chromosomes)1. Whilst at the initiation stage, aberrations are most easily recognised as breaks, acentric fragments, dicentrics and ring forms; those which survive cell division are found as stable alterations in the structure of chromosomes. "Human studies have illustrated a dose-response, a decrease over time following exposure, and persistence of a percentage of chromosomal aberrations up to 28 years following exposure"2. However the difficulty of recognising stable rearrangements in a small proportion of cells has limited this analysis for toxic chemical exposure, to very few laboratories.
The combined studies from 3 laboratories on 32,300 lymphocytes from 1,402 chromosomally normal individuals, determined a background rate of random structural abnormalities in lymphocytes of 1/587 cells3. These abnormalities were not age-related.
The G.C.A.T. laboratory has undertaken studies of two different groups of patients who had a high incidence of chronic fatigue syndrome (CFS). In some patients only 30 cells were examined but in the majority, 50 or more cells were examined. From the control data, in analyses of 30 cells per subject, we might expect to find 1 abnormality per 20 subjects whilst with 50 cells per subject, we might expect to find 1 abnormality per 11 subjects.
Stem 1: This study included 55 patients who were consecutively referred for cytogenetic analysis, because of either a previous chemical exposure or a diagnosis of chronic fatigue syndrome (CFS). 36 persons (65%) had at least one cell with a significant chromosome abnormality. The percentage of abnormal cells ranged from 1 - 18%. Chromosome abnormalities were only found in those with a previous chemical exposure. Patients with a diagnosis of CFS, but no chemical exposure, had no abnormalities. In this group of patients, the finding of chromosome abnormalities was correlated with both age (p = < .0001) and time since exposure (p = < .0001). These both seemed to reflect the inclusion of persons who had suffered from long and very severe illness, following very significant toxic exposures.
Study 2: A study of 45 patients (2 also included in study 1) comprised chemically exposed persons where clinical assessments have been recorded by Dr. Donohoe, and the details of exposure types and dates recorded. Severity of illness was graded on a scale of 0 (no illness) to 10 (bed bound, extreme) with a mean for the group of 6.5. For statistical analysis this was divided into 2 groups (from the data): less severe (3-6), more severe (7-9). Chromosome abnormalities were found in over 60% of the referred persons. The likelihood of finding a chromosomal abnormality was related to the overall severity of illness (Odds Ratio: 1.75 x, p = 0.02). CFS was not specifically related to the finding of a chromosomal abnormality and 7/8 patients without CFS had chromosome abnormalities.
It is concluded that chromosome analysis is a very useful tool in documenting a history of chemical exposure. Abnormalities are found in more than 60% of persons with histories of chemical exposures compared with 0.17% of an unselected population. CFS is usually found as one of the presenting symptoms in persons with such an exposure but CFS itself is not correlated with the presence, or absence, of chromosome abnormalities.
1. Report of the NTP Ad Hoc Panel on Chemical Carcinogenesis Testing and Evaluation (1984). US Dept. Health & Human Services.
2. Evans H J. (1982) Cytogenetic studies on Industrial Populations exposed to Mutagens", Banbury Report 13: Indictors on Genotoxic Exposure, Eds. B.A. Bridges, B.E. Butterworth and I.B. Weinstein, Cold Spring Harbor Laboratory, pp. 543-552
3. Hecht F. Kaiser McCaw B. Peakman D, Robinson A (1975) Non-random occurrence of 7-14 translocations in human lymphocyte cultures. Nature 255: 242-243
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