All available specimens were used in study, per CDC paper; "empirical" criteria used
I imagine that the CDC used patients that fit both the Empirical and Fukuda criteria and this cut down the number substantially..but there must've been more filtering involved I would think.
Apparently, there aren't very many suitable specimens archived from the CDC's studies in Wichita and Georgia, including the provider Registry. According to the paper, they tested ALL the specimens that were available from these studies - at least those that had enough "volume" to do their tests. This is what they say at pages 19-20 of the provisional pdf at
http://www.retrovirology.com/content/pdf/1742-4690-7-57.pdf (emphasis is mine):
Specimens were available from 89 persons (33 CFS and 56 well controls) from
the population-based case-control studies and 18 CFS persons from the Registry study
described above. Subjects were included based on availability of specimens, and
comprised 11 of 43 persons with CFS and 26 of 53 healthy controls from Wichita, KS
and 22 of 32 persons with CFS and 30 of 51 healthy controls from Georgia. ...Clinical and demographic characteristics of subjects with specimens available
for this study did not differ from those persons who did not have ample specimen
volumes and case-control matching was maintained.
And, remember, there is no distinction between "empiric / Reeves" and "Fukuda" in this or other current CDC papers. "Pre-Reeves Fukuda" has no independent meaning to Reeves or CDC any more.
If I remember correctly, the "Reeves / empirical" criteria were developed from the Wichita studies. Dolphin has some good posts on the "empirical" or "Reeves" criteria I should look back at, but I think the gist of one of his posts was speculating that the Wichita study came up with so embarrassingly few CFS cases under the "unfiltered" Fukuda criteria, that they came up with the "empirical / Reeves" criteria to get a larger number of CFS cases out of the study, or they wouldn't have had anything worth publishing about (please feel free to jump in and correct me or clarify here). I don't think there's any verified explanation for how they came up with the criteria.
So, when Reeves and CDC now talk about Fukuda criteria in current publications, they mean the Reeves / empirical criteria, which they rationalize as simply "operationalizing" Fukuda - though they have done absolutely no studies to validate that assertion.
Look at around pages 19 - 20 of the paper where they describe the study population, and you'll see them using the "Reeves/empirical" version of the criteria. That is what allows them to include as CFS (as severely impaired) at least one person who scored 100 out of 100 on the physical functioning scale of SF-36. (emphasis mine):
Subjects with CFS had been ill on average 13.9 years (median 11.15 yrs, range 3 - 40 yrs), were
severely fatigued (MFI General Fatigue 16.5, range 10 - 20; MFI Reduced Activity 12.8,
range 4 20) and severely impaired (SF-36 physical functioning 65.5, range 10 -100);
SF-36 bodily pain 48.8, range 12 84), and 3/33 (9%) reported sudden onset to their
illness.
Sorry for the long post.