Table 3: Illness characteristics by exercise test status (N = 177).

Normal results Abnormal results
(N = 66) (N = 111)
% (N) % (N)
Diagnosed by
    Medical doctor 89.4 (59) 98.2 (109)
    Alternative practitioner 1.5 (1) 0.0 (0)
    Self-diagnosed 9.1 (6) 1.8 (2)
Fatigue/Energy problem duration
    6-12 months 1.5 (1) 0.9 (1)
    1-2 years 3.0 (2) 2.7 (3)
    Longer than 2 years 80.3 (53) 81.1 (90)
    Since childhood or adolescence 15.2 (10) 15.3 (17)
Illness onset
    Within 24 hours 20.0 (13) 29.1 (32)
    Over 1 week 10.8 (7) 10.0 (11)
    Over 1 month 7.7 (5) 12.7 (14)
    Over 2-6 months 9.2 (6) 12.7 (14)
    Over 7-12 months 9.2 (6) 5.5 (6)
    Over 1-2 years 10.8 (7) 9.1 (10)
    Longer than 2 years 21.5 (14) 13.6 (15)
    Since childhood or adolescence 10.8 (7) 7.3 (8)
Course of illness
    Constantly getting worse 15.2 (10) 28.8 (32)
    Constantly improving 3.0 (2) 1.8 (2)
    Persisting 13.6 (9) 14.4 (16)
    Relapsing & remitting 12.1 (8) 9.0 (10)
    Fluctuating 56.1 (37) 45.9 (51)
Functional status *
    Bedridden/Walk around the house 27.3 (18) 44.5 (49)
    Can do light housework 43.9 (29) 38.2 (42)
    Able to work 28.8 (19) 17.3 (19)
Had PEM in past 6 months
    Yes 98.5 (65) 100.0 (111)
    No 1.5 (1) 0.0 (0)
PEM onset after activities
    1 hour or less 33.3 (9) 20.0 (8)
    2-3 hours 22.2 (6) 20.0 (8)
    4-10 hours 25.9 (7) 10.0 (4)
    11-13 hours 3.7 (1) 5.0 (2)
    14-23 hours 3.7 (1) 10.0 (4)
    More than 24 hours 11.1 (3) 35.0 (14)
Pre-illness level of exertion leads to PEM
    Yes 87.9 (58) 82.9 (92)
    No 12.1 (8) 17.1 (19)

*p < 0.05.