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ARTICLES: Ben Z. Katz, Yukiko Shiraishi, Cynthia J. Mears, Helen J. Binns, and Renee Taylor Chronic Fatigue Syndrome After Infectious Mononucleosis in Adolescents Pediatrics 2009; 124: 189-193 [Abstract] [Full text] [PDF]

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Figures quoted should be considered lower bounds given they have not been adjusted for refusals, etc

Tom Kindlon   (6 July 2009)

Figures quoted should be considered lower bounds given they have not been adjusted for refusals, etc 6 July 2009
Tom Kindlon, Information Officer (voluntary position) Irish ME/CFS Association Send letter to journal: Re: Figures quoted should be considered lower bounds given they have not been adjusted for refusals, etc tomkindlon{at}oceanfree.net Tom Kindlon	This is a useful contribution to the field and again shows that viruses (in this case EBV) can trigger Chronic Fatigue Syndrome (CFS). One point which I don't think is sufficiently clear to anyone who just reads the abstract is that these figures have not been adjusted for refusals, etc. In epidemiology in particular, numbers matter. All the percentages were calculated on the basis of the initial 301 patients but we do not have information on a percentage of these. For example: - "Six months after their IM diagnosis, 286 (95%) completed a telephone screening interview." (i.e. 5% did not) - "On the basis of the screening interview, 70 of these adolescents (24%) were considered not fully recovered. A clinical evaluation was completed for 53 (76%) of these 70 not fully recovered adolescents; 12 refused, 3 had exclusionary diagnoses (primary depression, transverse myelitis, or anorexia), and 2 did not meet the study criteria (the fatigue predated the IM or the subject was not able to complete the 6-month evaluation in a timely manner)" - I am not going to break down the list of others lost to follow-up as Figure 1 does it quite clearly: in total, of the 53 (of 70 who were considered not fully recovered), there was a cumulative loss of 10 at 24 months. Figure 1 has the caption, "Follow-up summary for screened nonrecovered participants (n=70). Three-digit numbers represent unique patient identifiers that were used throughout the study.". However in fact, it only includes information on 53. Note, this is not a criticism of patients being lost to follow-up, just demonstrating that the figures could be adjusted. For example, if we look at the 12 who refused clinical examination at six months and also include the patient who was not able to complete the 6 -month evaluation in a timely manner, we have a total of 13 patients. If the same proportion of them had CFS (i.e. 39/53) as the group that was evaluated, then a further 9.57 on average would have CFS on average. (Of course, one can't have half a person but given we do not know the exact figure, I will use the unrounded figure). This would give a figure of (39+9.57)/301 or 16.13% at 6 months rather than the 13% quoted. Other figures would also proportionally increase on average. If one used the percentage who completed the initial telephone screening instrument, the percentage would actually be (39+9.57)/286 or 16.98% (i.e. 17%) at 6 months. Conflict of Interest: None declared