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Table 3 Final cluster solution–demographic, genetic and CFS criteria adherence differences

From: Are there subgroups of chronic fatigue syndrome? An exploratory cluster analysis of biological markers

Cluster 1: Pain tolerant & good cognitions (n = 40) 2: Restored HPA dynamics (n = 15) 3: Orthostatic intolerance (n = 20) 4: Low-grade inflammation (n = 4) 5: Pain intolerant & poor cognitions (n = 33) 6: High vagal activity (n = 3) p-valuec
Sex-no. of males (%) 7 (17.5) 4 (26.7) 7 (35.0) 1 (25.0) 10 (30.3) 1 (33.3) 0.639
Age, years-mean [95% CI] 15.7 [15.3, 16.3] 15.7 [14.9, 16.5] 15.0 [14.2, 15.7] 16.5 [15.1, 18.0] 14.8 [14.3, 15.4] 15.4 [11.2, 19.6] 0.074
BMI, kg/m2-mean [95% CI] 22.3 [21.0, 23.1] 23.2[20.4, 26.1] 20.4 [17.9, 22.6] 22.8 [11.6, 33.9] 20.7 [19.4, 22.0] 18.3 [11.4, 25.1] 0.128
Disease duration, months-mean [95% CI] 19.4 [15.9, 22.9] 25.1 [10.8, 39.5] 22.0 [16.0, 27.9] 28.0 [n.a.] 19.3 [14.8, 23.9] 30.3 [n.a.] 0.538
Fukuda-no. fulfilling criteria (%)a 27 (71.1) 9 (60.0) 16 (80.0) 4 (100.0) 25 (78.1) 3 (100.0) 0.564
Canada-no. fulfilling criteria (%)b 13 (35.1) 3 (20.0) 6 (30.0) 1 (25.0) 22 (68.8) 1 (33.3) 0.006
COMT [SNP rs4680]-no. (%)
 AA 10 (25.0) 4 (26.7) 8 (40.0) 1 (25.0) 13 (39.4) 0 (0) 0.616
 AG/GG 30 (75.0) 11 (73.3) 12 (60.0) 3 (75.0) 20 (60.6) 3 (100.0)
SLC6A4 [5-HTTLPR allele & SNP rs25531]-no. (%)
 SS/SLG 11 (27.5) 3 (20.0) 2 (10.0) 3 (75.0) 9 (27.3) 1 (66.7) 0.139
 SA/LALG/LALA 29 (27.5) 20 (80.0) 18 (90.0) 1 (25.0) 24 (72.7) 2 (33.3)
  1. HPA: hypothalamus–pituitary–adrenal; BMI: Body mass index; SD: Standard deviation; ADRA2A: alpha-2A adrenergic receptor gene; COMT: Catechol-O-methyltransferase gene; ADRB2: beta-2 adrenergic receptor gene; SLC6A4: serotonin transporter (5-HTT) gene; C: Cytosine; G: Guanine; A: Adenosine; LPR: long tandem repeats; S: short allele; L: long allele
  2. aNumber of patients fulfilling the CDC Fukuda 1994 diagnostic criteria for Chronic Fatigue Syndrome [Fukuda 1994]
  3. bNumber of patients fulfilling the Canada 2003 diagnostic criteria for Chronic Fatigue Syndrome [Carruthers 2003]
  4. cUnadjusted p-values. The p-values are based on the Fischer exact test or one-way ANOVA, as appropriate. Only group 1–3 and 5 were used in the statistical analyses of continuous variables due to few participants in group 4 and 6