Table 1.

 Estimates used to determine parameters for decision model

Parameter	Distribution	Value (SE)	Source(s)
Data for decision tree
Prevalences	Dirichlet	Normal glucose tolerance 83%; impaired glucose tolerance 12%; type 2 diabetes 5%	STAR study24
Screening test efficiency	Multi-nominal	For type 2 diabetes: sensitivity 89.5%, specificity 91.3%; for impaired glucose tolerance and type 2 diabetes: sensitivity 59.4%, specificity 88.0%	STAR study24
Transition rates (per 100 person years)
Normal to impaired glucose tolerance:
<65 years	Log normal	1.66 (0.08)	Baltimore study33
≥65 years	Log normal	2.49 (0.11)
Impaired glucose tolerance to type 2 diabetes	Log normal	1.96 (0.25)	12 studies25-36
Time spent with undetected diabetes (years)	Log normal	1.65 (0.68)	Harris37
Mortality rates (per 100 person years)
45-54 years	—	0.32	DoH statistics (2000)
55-64 years	—	0.84
65-74 years	—	2.36
75-84 years	—	6.09
≥85 years	—	15.68
Increased risk of death with diabetes (hazard ratio)	Log normal	0.756 (0.087)	DECODE38
Increased risk of death for 1% increase in HbA1c (hazard ratio)	Log normal	0.104 (0.039)	Rossing39
Intervention effects on risk of developing type 2 diabetes (hazard ratio)
Lifestyle v standard treatment	Log normal	−0.646 (0.099)	12 studies6
Antidiabetic drugs v placebo	Log normal	−0.425 (0.141)	9 studies6
HbA1c
Undiagnosed diabetes	Normal	9.0% (0.056)	UKPDS40
Screen detected diabetes	Normal	7.0% (0.028)	UKPDS41
Clinically detected diabetes	Normal	7.9% (0.042)	UKPDS41
Utilities
Undiagnosed diabetes	Normal	0.788 (0.020)†	ADDITION34
Screen detected diabetes	Normal	0.788 (0.020)‡	ADDITION34
Clinically detected diabetes	Normal	0.771 (0.035)‡	UKPDS43 44
Costs*
Screening tests:
FPG test	—	£0.40/person	NHS (2006)
OGTT test	—	£1.30/person
Nurse cost	—	£26/hour	Curtis45
Metformin intervention	—	£16.10/year	NHS (2006)
Lifestyle intervention:
Year 1	—	£398/year	Avenell9
Subsequent years	—	£280/year
Undiagnosed diabetes:
Year before diagnosis	—	£114/year	Gulliford,46 Curtis45
Years 2-5 before diagnosis	—	£22/year
Diagnosed diabetes:
Screen detected	Normal	£2490 (53.3)/year	UKPDS47
Clinically detected	Normal	£2756 (63.1)/year

FPG=fasting plasma glucose; OGTT=oral glucose tolerance test.

*Costs are standardised to 2006.⁴⁸

†Constant for all time spent with undetected type 2 diabetes.

‡Starting utility, which was then decreased for each year spent with diabetes because of predicted increases in complications, based on UKPDS data.^{44 45}