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Table 3 Summary statistics for assessment of criterion and construct validity.

From: A questionnaire for determining prevalence of diabetes related foot disease (Q-DFD): construction and validation

  Kappa Sensitivity % Specificity % LR+ LR-
Samples B and C combined
(any diagnosis of DRFD)
0.64 85.0 (63.9, 94.8) 79.2 (59.5, 90.8) 4.1 (2.7, 6.2) 0.19 (0.09, 0.37)
Samples B and C combined
(all components of DRFD)
     
PN 0.70 85.7 (65.4, 95.0) 84.6 (66.5, 94.0) 5.6 (3.4, 9.3) 0.2 (0.09, 0.32)
PVD 0.60 83.3 (55.2, 95.3) 83.3 (68.1, 92.1) 5.0 (3.5, 7.2) 0.2 (0.07, 0.54)
Ulcer 0.90 91.7 (64.6, 98.5) 97.2 (85.8, 99.5) 33.0 (4.6, 238.0) 0.08 (0.01, 0.61)
Amputation 0.83 85.7 (48.7, 88.7) 97.5 (87.1, 99.6) 34.3 (4.6, 257.0) 0.14 (0.02, 1.04)
Deformity **      
Sample B
(any diagnosis of DRFD)
0.43 60.0 (23.1, 88.2) 84.6 (57.8, 95.7) 3.9 (0.95, 16.1) 0.47 (0.17, 1.3)
Sample B
(all components of DRFD)
     
PN 0.57 75.0 (40.9, 92.9) 84.6 (57.8, 95.7) 4.9 (1.6, 14.5) 0.29 (0.12, 0.8)
PVD 0.77 66.8 (20. 8, 93.9) 94.8 (75.4, 99.1) 12.7 (1.1, 147) 0.35 (0.05, 2.5)
Deformity 0.72 90.9 (62.3, 98.4) 72.7 (43.4, 90.3) 3.3 (1.7, 6.5) 0.13 (0.02, 1.0)
Sample C
(any diagnosis of DRFD)
0.67 93.0 (70.2, 98.8) 72.7 (43.4, 90.3) 3.4 (1.8, 6.6) 0.09 (0.01, 0.71)
Sample C
(all components of DRFD)
     
PN 0.84 92.3 (66.7, 98.6) 84.6 (57.8, 95.7) 6.0 (2.2, 16.2) 0.09 (0.01, 0.7)
PVD 0.61 88.9 (56.5, 98.0) 70.6 (46.9, 86.7) 3.0 (2.0, 4.6) 0.16 (0.02, 1.2)
Ulcer 1.00 91.7 (64.6, 98.5) 93.3 (70.2, 98.8) 13.8 (1.9, 99.0) 0.09 (0.01, 0.6)
Amputation 0.90 85.7 (48.7, 97.4) 94.7 (75.4, 99.1) 16.3 (2.2, 122.0) 0.14 (0.02, 1.0)
Sample C
(complications group, all components of DRFD)
     
PN 0.75 90.9 (62.3, 98.4) 66.7 (20.8, 93.9) 2.7 (0.38, 19.8) 0.14 (0.01, 1.6)
PVD 0.41 85.7 (48.7, 97.4) 42.9 (15.8, 75.0) 1.5 (0.9, 2.6) 0.33 (0.02, 5.7)
Ulcer 1.00 90.9 (62.3, 98.4) 75.0 (30.1, 95.4) 3.6 (0.5, 26.3) 0.12 (0.01, 1.1)
Amputation 0.85 85.7 (48.7, 97.4) 85.7 (48.7, 97.4) 6.0 (0.8, 45.0) 0.17 (0.02, 1.2)
Sample C
(no complications group, all components of DRFD)
     
PN 0.75 66.7 (20.8, 93.9) 90.0 (59.6, 98.2) 6.7 (0.6, 77.3) 0.4 (0.05, 2.7)
PVD 0.75 66.7 (20.8, 93.9) 90.0 (59.6, 98.2) 6.7 (0.6, 77.3) 0.4 (0.05, 2.7)
Ulcer 1.00 50.0 (9.5, 90.6) 91.7 (64.6, 98.5) 6.0 (0.12, 302.0) 0.55 (0.07, 3.9)
Amputation 1.00 50.0 (9.5, 90.6) 92.3 (66.7, 98.6) 6.5 (0.13, 328.0) 0.54 (0.07, 3.9)
  1. CI set at 95%, LR+ = positive likelihood ratio, LR- = negative likelihood ratio. No analysis for sample B for ulcer and amputation as no respondent reported either component. ** no combined analysis completed due to lack of deformity data in Sample C
  2. For Sample B (n = 21) correlation between survey findings and clinical assessment were analysed and for Sample C (n = 25) correlation between survey findings and medical record were analysed. Analysis was also undertaken for two subgroups of Sample C, one with known foot complications (n = 13) and one with no known foot complications (n = 12). Findings are reported for any diagnosis of DRFD (where any one of PN, PVD, ulcer, amputation or deformity were identified) and for the diagnosis of individual DRFD components.