Table 3

Ability of FPG and RPG to predict suboptimal glucose control among patients with type 2 diabetes without medical conditions thought to alter HbA1c reliability using different HbA1c thresholds

HbA1c cut-offTestNAUROC
(95% CI)
Equivalent threshold
(mmol/L)
Sensitivity
(95% CI)
Specificity
(95% CI)
PPV
(95% CI)
NPV
(95% CI)
Correctly classified (%)
48
(6.5%)
FPG1420.84
(0.77 to 0.92)
6.679.5
(70.8 to 86.5)
73.3
(54.1 to 87.7)
91.8
(84.4 to 96.4)
48.9
(33.7 to 64.2)
78.2
RPG1450.86
(0.80 to 0.92)
9.679.1
(70.6 to 86.1)
71.0
(52.0 to 85.8)
91.0
(83.6 to 95.8)
47.8
(32.9 to 63.1)
77.4
53
(7.0%)
FPG1420.87
(0.81 to 0.93)
7.181.0
(71.9 to 88.2)
71.4
(55.4 to 84.3)
87.1
(78.5 to 93.2)
61.2
(46.2 to 74.8)
78.2
RPG1450.88
(0.83 to 0.94)
10.581.6
(72.7 to 88.5)
72.1
(56.3 to 84.7)
87.5
(79.2 to 93.4)
62.0
(47.2 to 75.3)
78.8
58
(7.5%)
FPG1420.85
(0.79 to 0.91)
7.776.7
(66.6 to 84.9)
76.9
(63.2 to 87.5)
85.2
(75.6 to 92.1)
65.6
(52.3 to 77.3)
76.8
RPG1450.84
(0.77 to 0.90)
11.478.5
(68.8 to 86.3)
71.7
(57.7 to 83.2)
83.0
(73.4 to 90.1)
65.5
(51.9 to 77.5)
76.0
64
(8.0%)
FPG1420.86
(0.80 to 0.92)
8.474.0
(62.8 to 83.4)
81.5
(70.0 to 90.1)
82.6
(71.6 to 90.7)
72.6
(60.9 to 82.4)
77.5
RPG1450.84
(0.78 to 0.90)
12.478.8
(68.2 to 87.1)
80.3
(68.7 to 89.1)
82.9
(72.5 to 90.6)
75.7
(64.0 to 85.2)
79.5
69
(8.5%)
FPG1420.85
(0.79 to 0.91)
9.073.5
(61.4 to 83.5)
83.8
(73.4 to 91.3)
80.6
(68.6 to 89.6)
77.5
(66.8 to 86.1)
78.9
RPG1450.85
(0.79 to 0.91)
13.376.1
(64.5 to 85.4)
78.7
(67.7 to 87.3)
77.1
(65.6 to 86.3)
77.6
(66.6 to 86.4)
77.4
75
(9.0%)
FPG1420.85
(0.78 to 0.92)
9.674.1
(60.3 to 85.0)
80.7
(70.9 to 88.3)
70.2
(56.6 to 81.6)
83.5
(73.9 to 90.7)
78.2
RPG1450.85
(0.78 to 0.92)
14.475.0
(61.6 to 85.6)
77.8
(67.8 to 85.9)
67.7
(54.7 to 79.1)
83.3
(73.6 to 90.6)
76.7
  • AUROC, sensitivity, specificity, % correctly classified, PPV and NPV are given for the respective optimal thresholds of the test. This was restricted to HbA1c where there were no conditions thought to alter HbA1c reliability like anemia, sickle cell traits, and renal impairment.

  • The units used are mmol/L for fasting and random non-fasting glucose.

  • AUROC, area under receiver operating characteristic curve; FPG, fasting plasma glucose; HbA1c, glycosylated hemoglobin; NPV, negative predictive value; PPV, positive predictive value; RPG, random non-fasting plasma glucose.