the study was approved by the emory university institutional review board and used data from 1,573 adults in the sigt study , described previously ( 5 ) .
briefly , this study recruited participants without known diabetes between january 2005 and march 2008 .
the participants first visits were at different times of the day , without an overnight fast .
rcg and rpg were measured , a 50-g glucose drink was given , and gctcap and gctpl glucose levels were measured 1 h later . at a second visit , a1c was measured and a 75-g oral glucose tolerance test ( ogtt ) was begun before 11:00 a.m. , after an overnight fast .
diabetes included fasting glucose 126 mg / dl ( 7 mmol / l ) or 2-h ogtt glucose 200
mg / dl ( 11.1 mmol / l ) ; a1c 6.5% ( 48 mmol / mol ) was included in sensitivity analyses .
our definition of prediabetes110 included the following : ifg110 , which is fasting glucose 110125 mg / dl ( 6.16.9 mmol / l ) and 2-h ogtt glucose < 140 mg / dl ( 7.8 mmol / l ) ; igt , which is fasting glucose < 110 mg / dl and 2-h ogtt glucose 140199 mg / dl ( 7.811.1 mmol / l ) ; and ifg110 with igt ( ifg plus igt ) , which is fasting glucose 110125 mg / dl ( 6.16.9 mmol / l ) and 2-h ogtt glucose 140199 mg / dl ( 7.811.1 mmol / l ) .
cost components and base - case cost assessment also are shown in supplementary table 1 .
health system costs were costs that would be incurred in a united states health care system with the government - funded medicare program as the primary health insurer
. included were direct medical costs associated with testing , direct medical costs of false - negative results , and direct medical costs for treatment of true - positive results ( including cases of prediabetes110 and diabetes ) with generic metformin .
two cost scenarios were considered , health system costs of screening and treatment for dysglycemia110 and health system costs for screening and treatment of diabetes only .
all cost scenarios were calculated for a 3-year period of time . the direct medical costs of testing included 2007 medicare costs for the laboratory tests , the cost of the glucose challenge test glucose drink , as well as staff costs based on 2007 united states bureau of labor services wages .
we assumed that blood draws for gctpl , rpg , and ogtt assessments would be obtained on - site , and that medical staff would measure rcg and gctcap . because we assumed that initial screening would be opportunistic during a visit , the visit time was not included .
we used 70% specificity cut - offs to define positive screen results for each test to detect diabetes or dysglycemia110 , using the ogtt data , to determine these cut - offs .
for our cost analyses , we assumed that those participants with a positive screen result would have a subsequent confirmatory ogtt with fasting and postchallenge glucose cut - offs for prediabetes110 and diabetes as defined .
the cost of a false - positive result for each screen included the cost of the follow - up ogtt test as per protocol . for the base - case analyses
undetected prediabetes110 or diabetes  as 10% of the projected incremental 3-year medical costs for that condition , assuming that these incremental costs could be decreased by appropriate management , as they were in the diabetes prevention program ( dpp ) ( 8,9 ) .
we assumed that the cost of a false - negative result would include the 3-year direct medical cost of diabetes , prediabetes110 , or prediabetes110 that progressed to diabetes .
we based the direct medical costs for diabetes on medical expenditure panel survey costs from 2000 to 2004 , which was $ 4,174 per year in 2005 united states dollars for a 50-year - old with new - onset diabetes ( 10 ) .
we calculated the costs for prediabetes based on the cost of patients with ifg110 in kaiser permanente northwest who had incremental direct medical costs of $ 1,316 per year ( 11 ) , although igt might incur higher costs ( 12 ) .
we based the direct medical costs for a true positive result ( prediabetes110 or diabetes ) on 3-year costs for the dpp metformin group .
this group s incremental costs for laboratory tests , physician visits , and follow - up were $ 703 ( 9 ) .
we assumed that all true - positive results would be treated with metformin , and we substituted recent pharmacy - based generic costs for metformin 850 mg twice per day .
the direct medical cost incurred outside of the study for the dpp metformin versus placebo arms was used as the other component for the health system cost of true - positive results ( 9 ) ; the direct medical cost outside the study was $329 for the metformin versus placebo arms .
we analyzed costs for subgroups of our study population based on the presence of the following risk characteristics : age < 40 , age 4055 , and age > 55 years ; bmi < 25 , 2535 , > 35
kg / m ; waist circumference with cut - offs of < 88 cm in men and < 102 cm in women ( low - risk ) or 88 cm in men and 102 cm in women ( high - risk ) ; triglycerides < 150 mg / dl ( 1.695 mmol / l ; low - risk ) or 150 mg / dl ( 1.695 mmol / l ; high - risk ) ; hdl 40 mg / dl ( 1.036 mmol / l ) in men and 50 mg / dl ( 1.295 mmol / l ) in women ( low - risk ) or < 40 mg / dl ( 1.036 mmol / l ) in men and < 50 mg / dl ( 1.295 mmol / l ) in women ( high - risk ) ; presence or absence of a family history of diabetes in first - degree relatives ; and presence or absence of elevated blood pressure , defined as systolic blood pressure < 130 ( low - risk ) or 130 mmhg ( high - risk ) . for each characteristic ,
we examined the costs when we included a1c results of 6.5% ( 48 mmol / mol ) in the definition of diabetes .
we examined the following alternatives for the cost components to determine whether our findings were robust : substituting veterans affairs system costs for testing and treatment with metformin to provide a single - payer perspective ; using lower costs for false - negative results , assuming 5% of projected incremental 3-year medical costs , similar to the outside medical care costs of participants in the dpp ( 8) ; and using costs for treatment with lifestyle modification rather than metformin , assuming group intervention costs and costs for other lifestyle changes as described in the dpp protocol ( 13 ) .
societal costs included the additional nonmedical costs of testing , indirect ( lost labor productivity ) costs of false - negative results , and direct nonmedical and indirect costs of true - positive results .
indirect costs for false - negative results ( absenteeism , reduced productivity at work and for those who did not work ) were derived from the american diabetes association 2007 economic assessment and were attributed only to those with diabetes or whose prediabetes progressed to diabetes during the 3 years ( 14 ) .
costs of screening and treatment were expressed as mean  sem for the five types of screens for each risk group .
we compared overall high - risk versus low - risk group costs as average costs for the seven higher - risk or highest - risk versus lower - risk or lowest - risk groups .
we used nonparametric mann - whitney tests for statistical comparisons of cost variables using sas 9.1.3 ( sas institute , cary nc ) ( 15 ) .
diabetes included fasting glucose 126 mg / dl ( 7 mmol / l ) or 2-h ogtt glucose 200 mg / dl ( 11.1 mmol / l ) ; a1c 6.5% ( 48 mmol / mol ) was included in sensitivity analyses .
our definition of prediabetes110 included the following : ifg110 , which is fasting glucose 110125 mg / dl ( 6.16.9 mmol / l ) and 2-h ogtt glucose < 140 mg / dl ( 7.8 mmol / l ) ; igt , which is fasting glucose < 110 mg / dl and 2-h ogtt glucose 140199 mg / dl ( 7.811.1 mmol / l ) ; and ifg110 with igt ( ifg plus igt ) , which is fasting glucose 110125 mg / dl ( 6.16.9 mmol / l ) and 2-h ogtt glucose 140199 mg / dl ( 7.811.1 mmol / l ) .
cost components and base - case cost assessment also are shown in supplementary table 1 .
health system costs were costs that would be incurred in a united states health care system with the government - funded medicare program as the primary health insurer . included were direct medical costs associated with testing , direct medical costs of false - negative results , and direct medical costs for treatment of true - positive results ( including cases of prediabetes110 and diabetes ) with generic metformin .
two cost scenarios were considered , health system costs of screening and treatment for dysglycemia110 and health system costs for screening and treatment of diabetes only .
the direct medical costs of testing included 2007 medicare costs for the laboratory tests , the cost of the glucose challenge test glucose drink , as well as staff costs based on 2007 united states bureau of labor services wages .
we assumed that blood draws for gctpl , rpg , and ogtt assessments would be obtained on - site , and that medical staff would measure rcg and gctcap . because we assumed that initial screening would be opportunistic during a visit , the visit time was not included .
we used 70% specificity cut - offs to define positive screen results for each test to detect diabetes or dysglycemia110 , using the ogtt data , to determine these cut - offs .
for our cost analyses , we assumed that those participants with a positive screen result would have a subsequent confirmatory ogtt with fasting and postchallenge glucose cut - offs for prediabetes110 and diabetes as defined .
the cost of a false - positive result for each screen included the cost of the follow - up ogtt test as per protocol .
for the base - case analyses , we evaluated the cost of a false negative result 
undetected prediabetes110 or diabetes  as 10% of the projected incremental 3-year medical costs for that condition , assuming that these incremental costs could be decreased by appropriate management , as they were in the diabetes prevention program ( dpp ) ( 8,9 ) .
we assumed that the cost of a false - negative result would include the 3-year direct medical cost of diabetes , prediabetes110 , or prediabetes110 that progressed to diabetes .
we based the direct medical costs for diabetes on medical expenditure panel survey costs from 2000 to 2004 , which was $ 4,174 per year in 2005 united states dollars for a 50-year - old with new - onset diabetes ( 10 ) .
we calculated the costs for prediabetes based on the cost of patients with ifg110 in kaiser permanente northwest who had incremental direct medical costs of $ 1,316 per year ( 11 ) , although igt might incur higher costs ( 12 ) .
we based the direct medical costs for a true positive result ( prediabetes110 or diabetes ) on 3-year costs for the dpp metformin group .
this group s incremental costs for laboratory tests , physician visits , and follow - up were $ 703 ( 9 ) .
we assumed that all true - positive results would be treated with metformin , and we substituted recent pharmacy - based generic costs for metformin 850 mg twice per day .
the direct medical cost incurred outside of the study for the dpp metformin versus placebo arms was used as the other component for the health system cost of true - positive results ( 9 ) ; the direct medical cost outside the study was $329 for the metformin versus placebo arms .
we analyzed costs for subgroups of our study population based on the presence of the following risk characteristics : age < 40 , age 4055 , and age > 55 years ; bmi < 25 , 2535 , > 35
kg / m ; waist circumference with cut - offs of < 88 cm in men and < 102 cm in women ( low - risk ) or 88 cm in men and 102 cm in women ( high - risk ) ; triglycerides < 150 mg / dl ( 1.695 mmol / l ; low - risk ) or 150 mg / dl ( 1.695 mmol / l ; high - risk ) ; hdl 40 mg / dl ( 1.036 mmol / l ) in men and 50 mg / dl ( 1.295 mmol / l ) in women ( low - risk ) or < 40 mg / dl ( 1.036 mmol / l ) in men and < 50 mg / dl ( 1.295 mmol / l ) in women ( high - risk ) ; presence or absence of a family history of diabetes in first - degree relatives ; and presence or absence of elevated blood pressure , defined as systolic blood pressure < 130 ( low - risk ) or 130 mmhg ( high - risk ) . for each characteristic ,
we examined the costs when we included a1c results of 6.5% ( 48 mmol / mol ) in the definition of diabetes .
we examined the following alternatives for the cost components to determine whether our findings were robust : substituting veterans affairs system costs for testing and treatment with metformin to provide a single - payer perspective ; using lower costs for false - negative results , assuming 5% of projected incremental 3-year medical costs , similar to the outside medical care costs of participants in the dpp ( 8) ; and using costs for treatment with lifestyle modification rather than metformin , assuming group intervention costs and costs for other lifestyle changes as described in the dpp protocol ( 13 ) .
societal costs included the additional nonmedical costs of testing , indirect ( lost labor productivity ) costs of false - negative results , and direct nonmedical and indirect costs of true - positive results .
indirect costs for false - negative results ( absenteeism , reduced productivity at work and for those who did not work ) were derived from the american diabetes association 2007 economic assessment and were attributed only to those with diabetes or whose prediabetes progressed to diabetes during the 3 years ( 14 ) .
costs of screening and treatment were expressed as mean  sem for the five types of screens for each risk group .
we compared overall high - risk versus low - risk group costs as average costs for the seven higher - risk or highest - risk versus lower - risk or lowest - risk groups .
we used nonparametric mann - whitney tests for statistical comparisons of cost variables using sas 9.1.3 ( sas institute , cary nc ) ( 15 ) .
baseline characteristics of participants have been reported previously and are shown in table 1 ; 366 ( 23% ) had dysglycemia110 and 72 ( 5% ) had diabetes .
more than 75% of participants were 45 years of age or older or had bmi 25 kg / m .
however , only 12% had a triglyceride level 150 mg / dl ( 1.695 mmol / l ) , 26% had systolic blood pressure 130 mmhg , and 46% had a family history of diabetes .
the higher - risk groups were more likely to have diabetes or dysglycemia110 ; the latter was present in 35% of participants with age > 55 years , bmi > 35 kg / m , or systolic blood pressure 130 mmhg compared with 1019% in the corresponding lower - risk groups .
baseline characteristics of 1,573 participants from the sigt study the health system cost components and overall assessment for screening ( and 3 years of treatment ) for dysglycemia110 are shown in supplementary table 1 . these health system costs and the differences in health system costs for screening versus no screening are shown by risk group for each screening test in table 2 and fig . 1 ;
in these analyses ,  negative cost differences  for screening versus no screening indicate projected net 
cost - savings .  the relative cost - savings of screening versus no screening would be greater ( more  negative  ) for the higher - risk groups for every risk group assessed ( p < 0.01 for each higher - risk or highest - risk versus lower - risk or lowest - risk group ) , with average cost - savings of 19% for the highest bmi and 18% for the elevated blood pressure groups ( both p < 0.01 compared with lowest - risk and lower - risk groups ) . among the different tests ,
screening of the higher - risk groups was generally least expensive when gctpl was used for screening , with cost - savings of 21% for the highest bmi and elevated blood pressure groups .
screening lower - risk groups would result in less cost - savings , or a net increase in costs , and in those groups rpg or rcg tended to be the least expensive tests .
health system costs for screening and treatment of dysglycemia110 of 1,573 participants by risk group and percent cost difference for screening and treatment compared with no screening * the average percent cost differences between health system costs for screening and treatment of dysglycemia110 by risk group compared with no screening . shown
are the average percent differences in cost for screening with the five different screens and management of dysglycemia110 compared with no screening for different risk groups .
the 95% cis are depicted by the upper or lower lines or both . for each risk group ,
the prevalence of dysglycemia110 is shown along the top of the chart , and the costs of no screening per person are shown along the bottom of the chart .
the prevalence of dysglycemia110 and the cost of no screening per person increased with higher - risk characteristics among the risk groups .
sbp , systolic blood pressure ; tg , triglycerides ; fam hx , family history .
the health system costs for screening ( and treatment ) for diabetes are shown in table 3 , with the differences in costs for screening versus no screening in table 3 and supplementary fig .
1 . for all of these groups , screening would produce cost - savings compared with no screening , and cost - savings with targeting of diabetes would be greater than with dysglycemia110 ( for all subjects , cost - savings of 26 vs. 9% ; p < 0.01 ) . as with dysglycemia110
, cost - savings resulting from screening for diabetes would be greater with higher - risk and highest - risk groups compared with lower - risk and lowest - risk groups ( 34 vs. 12% , over all groups ; p < 0.01 ) ; screening those with elevated blood pressure , the highest bmi , and the oldest age groups would provide the greatest cost - savings ( 39 , 38 , and 36% , respectively ; all p < 0.01 versus the relevant lowest - risk group ) .
gctpl testing would provide the lowest costs for the higher - risk groups , with cost - savings of up to 46% for those with elevated blood pressure , and rcg or rpg would provide the lowest costs with the lowest - risk groups .
health system costs for screening and treatment of diabetes of 1,573 participants by risk group and percent cost difference for screening and treatment compared with no screening * the impact of screening on overall costs depends on the prevalence of the disease in the population , the cost of undetected disease ( false - negative results ) , the cost of screening , and characteristics of different screening tests . with our study population and base - case assumptions , cost - savings for screening with gctpl versus rcg
would be achieved in screening for diabetes when the prevalence in the population is 4% and for dysglycemia110 when the prevalence is 20% ( supplementary fig .
is shown in supplementary table 2 and is illustrated for screening with gctpl versus rcg in supplementary fig .
greater cost - savings are achieved with gctpl , a more accurate but more expensive test , either when cost of undetected disease is high or when prevalence of disease is high , and especially when both are high .
testing costs per true - positive result also decrease as prevalence of the disease in the population increases .
in screening for dysglycemia110 , average testing costs for the five screens for those with bmi < 25 kg / m would be $ 203  40 per true - positive result compared with $ 64  7 for those with bmi > 35 kg / m ( p < 0.01 ) .
in screening for diabetes , average testing costs per true - positive result would be $ 836  156 for those with bmi < 25
kg / m compared with $ 185  17 for those with bmi > 35 kg / m ( p < 0.01 ) .
when we included a1c 6.5% ( 48 mmol / mol ) in our definition of diabetes , we identified 10 additional participants with diabetes in this cohort ; however , the total number of participants with dysglycemia110 did not change .
screening the higher - risk groups for diabetes continued to be significantly more cost - saving compared with no screening and compared with screening the equivalent low - risk group .
for example , screening with gctpl for those with an elevated blood pressure versus those without an elevated blood pressure resulted in cost - savings of 37.5 versus 2.5% , respectively ( p < 0.01 ) , both compared with no screening . for both higher - risk and lower - risk groups , screening for dysglycemia110 or diabetes from a veterans affairs perspective would result in greater cost - savings compared with medicare - based costs ( supplementary tables 4 and 5 ) if false - negative result costs were only 5% of projected incremental medical costs over 3 years , then health system costs would be cost - neutral for screening for diabetes compared with no screening for some but not all of the higher - risk groups ( supplementary table 6 ) , but screening and treatment of dysglycemia110 would not produce cost - savings for any group ( not shown ) .
the health system costs with a lifestyle change intervention would be similar to costs with generic metformin , with cost - savings particularly for higher - risk groups ( supplementary tables 7 , 8) . from a societal perspective ,
screening ( and treatment with metformin ) for dysglycemia110 ( supplementary table 9 ) would result in cost - savings compared with no screening only in the highest - risk groups with substantial prevalence of disease , particularly for those with bmi > 35 kg / m or elevated blood pressure , with 11% savings compared with no screening . in contrast , societal costs for screening and treatment of diabetes ( supplementary table 10 ) would produce broader cost - savings in both high - risk and lower - risk groups .
when we included a1c 6.5% ( 48 mmol / mol ) in our definition of diabetes , we identified 10 additional participants with diabetes in this cohort ; however , the total number of participants with dysglycemia110 did not change .
screening the higher - risk groups for diabetes continued to be significantly more cost - saving compared with no screening and compared with screening the equivalent low - risk group .
for example , screening with gctpl for those with an elevated blood pressure versus those without an elevated blood pressure resulted in cost - savings of 37.5 versus 2.5% , respectively ( p < 0.01 ) , both compared with no screening . for both higher - risk and lower - risk groups , screening for dysglycemia110 or diabetes from a veterans affairs perspective would result in greater cost - savings compared with medicare - based costs ( supplementary tables 4 and 5 ) if false - negative result costs were only 5% of projected incremental medical costs over 3 years , then health system costs would be cost - neutral for screening for diabetes compared with no screening for some but not all of the higher - risk groups ( supplementary table 6 ) , but screening and treatment of dysglycemia110 would not produce cost - savings for any group ( not shown ) .
the health system costs with a lifestyle change intervention would be similar to costs with generic metformin , with cost - savings particularly for higher - risk groups ( supplementary tables 7 , 8) . from a societal perspective ,
screening ( and treatment with metformin ) for dysglycemia110 ( supplementary table 9 ) would result in cost - savings compared with no screening only in the highest - risk groups with substantial prevalence of disease , particularly for those with bmi > 35 kg / m or elevated blood pressure , with 11% savings compared with no screening .
in contrast , societal costs for screening and treatment of diabetes ( supplementary table 10 ) would produce broader cost - savings in both high - risk and lower - risk groups .
our previous analyses demonstrated that screening the sigt study population for either diabetes or dysglycemia110 would be cost - saving from a health system perspective over a 3-year horizon ( 4 ) .
we now show that the majority of cost - savings would come from screening individuals with higher risk , based on any one of the characteristics of age , bmi , triglycerides , hdl cholesterol , waist circumference , systolic blood pressure , or family history of diabetes . in most of the higher - risk groups ,
however , the greatest cost - savings would be attained with screening of individuals with bmi > 35 kg / m or systolic blood pressure 130 mmhg .
of the five screening tests considered , the gctpl appears to be the least expensive screening test in most higher - risk groups .
higher - risk groups would have higher costs associated with no screening . because these groups have a higher prevalence of diabetes and dysglycemia110 , failure to screen would result in more patients with missed diagnoses , with associated increases in downstream treatment costs . and as the costs of no screening increase , greater cost - savings can be obtained with a more accurate test , i.e. , gctpl compared with rcg ( supplementary fig .
one review concluded that it would be very cost - effective to screen for diabetes using current american diabetes association guidelines among african americans 4554 years of age ( 16 ) .
another study examined screening with fasting plasma glucose on the basis of age or blood pressure or both and found that it would be more cost - effective to screen at 3045 years of age than at older age , and even more cost - effective to screen beginning at 30 years of age in people with hypertension ( 2 ) .
two other studies found that targeted screening for diabetes with fasting or rcg based on hypertension , and for prediabetes based on obesity , would be more cost - effective compared with universal screening ( 17,18 ) , but those studies also did not consider other risk factors or other screening tests . whether screening should target prediabetes as well as diabetes also has been debated .
most analyses have found that it should be cost - effective to screen for and treat prediabetes to reduce both the risk of cardiovascular disease and progression to diabetes ( 1820 ) .
our study confirms that even over a 3-year time period , it should be cost - saving to screen for and treat dysglycemia110 ( prediabetes110 as well as diabetes ) , particularly among higher - risk groups .
the study participants were volunteers , which might have resulted in selection bias from disproportionate participation of those at high risk .
however , the prevalence of prediabetes and diabetes in the study population was similar to or lower than that in recent national surveys , such as nhanes 20052006 ( 21 ) .
although we did gather information regarding risk of diabetes , information on history of gestational diabetes was not collected or used as a risk factor in our analyses .
we also did not calculate costs associated with screening for either dysglycemia110 or diabetes with a fasting glucose alone .
whereas a fasting glucose may be considered an acceptable test for patients who do not mind fasting before a visit , many cases of postchallenge dysglycemia would be missed , leading to a higher number of false - negative results and higher overall costs .
our analyses rely on estimates of testing , treatment , and false - negative result costs , which may not be applicable to every health system .
our estimates for the cost of false - negative results ( that 10% of projected incremental 3-year medical costs of diabetes or dysglycemia110 could be reduced with detection and management ) might be excessive .
however , we project that cost - savings still could be achieved in higher - risk groups with a false - negative result cost of at least 5% , which was achieved in the tightly controlled environment of the dpp study ( 8) .
some groups have found the cost of undiagnosed diabetes and prediabetes to be lower than the costs we used in our analyses , but it is still to be determined how much of these costs could be reduced with detection and management ( 22,23 ) .
we are not aware of other sources for the costs of false - negative results . in sensitivity analyses addressing costs associated with lifestyle changes as treatment for dysglycemia110 or diabetes , we based our costs on group - based interventions designed by the dpp study .
more recent studies have found that community - based interventions based on the dpp protocol could be performed with reduced costs .
these studies generally have found that treatment with lifestyle interventions are cost - effective in the long - term ( 2426 ) and possibly even are cost - saving in the short - term ( 26 ) . finally , our cost estimates projected a 3-year time period .
such a period might be relevant to employer - based health systems in which insurers are changed every few years , but lifetime cost analyses would be needed to determine if the cost - savings found in higher - risk groups are likely to be sustained .
our findings show that screening and treatment for diabetes and dysglycemia110 should be cost - saving from a health system perspective in people with any single risk factor for these conditions .
this likely is a large proportion of the united states adult population , because at least one such risk factor was present in 98% of our study subjects and in 96% of adult african american and white participants in nhanes 20052006 .
we also found that the greatest cost - savings likely would be attained with screening of individuals with bmi > 35 kg / m , systolic blood pressure 130 mmhg , or age > 55 years .
the gctpl , previously shown to have the greatest accuracy for detection of diabetes or dysglycemia110 , appears to be the least expensive screening test in most higher - risk groups and should be considered for use in clinical practice .
 objectivealthough screening for diabetes and prediabetes is recommended , it is not clear how best or whom to screen . 
 we therefore compared the economics of screening according to baseline risk.research design and methodsfive screening tests were performed in 1,573 adults without known diabetes  random plasma / capillary glucose , plasma / capillary glucose 1 h after 50-g oral glucose ( any time , without previous fast , plasma glucose 1 h after a 50-g oral glucose challenge [ gctpl]/capillary glucose 1 h after a 50-g oral glucose challenge [ gctcap ] ) , and a1c  and a definitive 75-g oral glucose tolerance test . 
 costs of screening included the following : costs of testing ( screen plus oral glucose tolerance test , if screen is positive ) ; costs for false - negative results ; and costs of treatment of true - positive results with metformin , all over the course of 3 years . 
 we compared costs for no screening , screening everyone for diabetes or high - risk prediabetes , and screening those with risk factors based on age , bmi , blood pressure , waist circumference , lipids , or family history of diabetes.resultscompared with no screening , cost - savings would be obtained largely from screening those at higher risk , including those with bmi > 35 kg / m2 , systolic blood pressure 130 mmhg , or age > 55 years , with differences of up to 46% of health system costs for screening for diabetes and 21% for screening for dysglycemia110 , respectively ( all p < 0.01 ) . 
 gctpl would be the least expensive screening test for most high - risk groups for this population over the course of 3 years.conclusionsfrom a health economics perspective , screening for diabetes and high - risk prediabetes should target patients at higher risk , particularly those with bmi > 35 kg / m2 , systolic blood pressure 130 mmhg , or age > 55 years , for whom screening can be most cost - saving . 
 gctpl is generally the least expensive test in high - risk groups and should be considered for routine use as an opportunistic screen in these groups . 
RESEARCH DESIGN AND METHODS
Case definitions
Cost perspectives
Costs of testing
Costs of false-positive results
Costs of false-negative results
Costs of true-positive results
Risk group stratification
Sensitivity analyses
Statistical analyses
RESULTS
Sensitivity analyses
CONCLUSIONS