# Table 4 Comparison of QDIS-7 means and reliability estimates, five disease groups

Disease Mean (SD)a % with IRT Reliability ≥0.90 by Severity Levelb Alphac Test-retest reliabilityd
Mild Moderate Severe Total
Arthritis 54.24 (8.72) (N = 718) (N = 587) (N = 231) (N = 1536) .94 .88
60.5 93.5 95.7 78.4
CKD 48.97 (9.17) (N = 200) (N = 61) (N = 36) (N = 297) .94 .91
34.5 82.0 94.4 51.5
Cardiovascular 51.65 (9.87) (N = 483) (N = 112) (N = 36) (N = 631) .94 .90
55.5 95.5 91.7 64.7
Diabetes 47.60 (7.75) (N = 921) (N = 329) (N = 63) (N = 1313) .91 .83
38.6 72.0 100.0 49.9
Respiratory 48.45 (9.45) (N = 1152) (N = 306) (N = 112) (N = 1570) .94 .88
36.4 87.3 93.8 50.4
1. Abbreviations: CKD chronic kidney disease
2. aAnalysis of variance indicated that QDIS-7 group means differed across disease groups (F(4,5413) = 152.1, p < 0.0001). QDIS-7 scores have mean = 50, SD = 10 in chronically-ill US general population; higher scores equal worse health
3. bPercent with IRT estimated reliability ≥0.90. Severity defined as Mild (None, Mild), Moderate, or Severe (Severe, Very Severe) in response to item How would you rate the severity of your < condition > in the past 4 weeks?
4. cInternal consistency reliability for arthritis (N = 1113), CKD (N = 261), cardiovascular (N = 578), diabetes (N = 857) and respiratory groups (N = 1156)
5. dIntraclass correlation coefficient (ICC(3,1)) for arthritis (N = 109), CKD (N = 37), cardiovascular (N = 63), diabetes (N = 75) and respiratory groups (N = 92)