home 
 testing for chlamydia and gonorrhea has high sensitivity ( about 90% ) and 
 specificity ( > 99% ) , and is well accepted in adolescent and young adult 
 populations [ 13 ] .
studies in the us and in denmark demonstrate that 
 home testing significantly increases the likelihood that tests will occur [ 1 , 2 ] .
it is well established that office - based screening 
 for chlamydia is a cost - effective intervention for sexually active young women [ 35 ] , as is screening 
 for gonorrhea in women with individual or population risk factors [ 6 , 7 ] , however 
 screening in clinical settings is not performed as often as is recommended [ 8 , 9 ] .
home 
 screening , while increasing test frequency , might decrease screening costs , by 
 avoiding clinical facility and clinician fees .
the indirect costs of clinic - based screening , 
 such as time off work or school , childcare , transportation , and other costs resulting 
 from a clinic visit , could also be averted . 
 in this analysis
, we use test frequency and cost data from a randomized 
 trial of home testing for chlamydia and gonorrhea in high - risk young women to 
 examine cost differences between home - based and clinic - based testing and the 
 cost - effectiveness of a home testing intervention .
the data source for this analysis was the detection acceptability intervention for 
 std s in young women ( daisy ) study , a randomized controlled trial .
briefly , 398 young women aged 1524 at high 
 risk for std were recruited from clinics and surrounding communities , 
 representing a group where frequent testing is recommended .
women were randomized to an 
 intervention group , who received home testing kits for chlamydia and gonorrhea by 
 mail at 6 , 12 , and 18 months , or a control group , who received a postcard at 6 , 
 12 , and 18 months inviting them to attend one of the participating study 
 clinics for a routine test for women s health infections at no cost .
participants were urged to maintain their 
 usual health patterns , including evaluation for genital symptoms or std s . women with positive home tests
were notified , 
 counseled about partner notification , and referred to a participating clinic 
 for treatment at no cost .
significantly 
 more screening tests were performed in the home screening intervention group , 
 and no differences in std incidence rates were seen between intervention and 
 control groups over the study period . all participants 
 completed a questionnaire at enrollment , which included questions about out - of - pocket 
 costs for seeking or receiving care at the clinic , time off work or school due 
 to clinic visits , and time donated by others to allow the participant to attend 
 clinic .
these questions and the number of tests performed in clinic and at home 
 in the trial are the focus of this analysis .
the 
 direct and indirect costs of receiving screening tests were calculated for 
 women randomized to the intervention ( testing at home ) and for those in the 
 control group ( clinic testing ) .
direct 
 costs of clinic - based testing were the costs for clinician time and for the 
 test kit ( nucleic acid amplification for chlamydia and gonorrhea ) , along with 
 required supplies .
the panel on 
 cost - effectiveness in health and medicine recommends including the following as 
 indirect costs of care : payments made by the patient in the course of seeking 
 or receiving care , and time required by the patient and others to allow care to 
 be received . in this analysis ,
indirect costs for the clinic 
 visits included costs of parking or transportation and of babysitting or childcare .
indirect costs for time missed from school or 
 work to receive care and for time donated by others ( e.g. , for rides or 
 babysitting ) to allow care to occur were quantified based on patient responses , 
 then valued based on the average hourly wage in 2005 for nonfarm workers in the 
 us   to avoid bias against intervention in this 
 young population ; the effects of 
 other time costs were examined in sensitivity analyses .
direct costs for home screening were the cost 
 of the test , packaging costs , and postage to and from the patient , costing a 
 total of 25 .
testing cost alone ( including 
 materials and technician time ) in either setting was 21 .
these costs were then applied to clinic - based 
 and home - based tests as quantified in the daisy study , and costs compared 
 between intervention and control groups . 

alternative values for all cost components , varied individually and 
 collectively over plausible ranges , were examined in one - way and multiway 
 sensitivity analyses .
direct costs per subject for the intervention group and the control group were 
 calculated as follows : direct cost ( clinic test ) * clinic test frequency + direct cost ( home test ) * home test frequency divided by the number of subjects in each group .
cost - effectiveness 
 calculations were performed to estimate the cost per additional test performed 
 per subject , using the formula ( 1)total cost per subject ( intervention)total cost per subject ( control)tests per subject ( intervention)tests per subject ( control ) .
the model assumes equal std 
 incidence and diagnosis with home- and clinic - based testing , as seen in the 
 daisy trial , and hence the advantage of home testing from a cost - effectiveness 
 standpoint ( if any ) is that , compared to the clinic testing group , more tests are 
 performed overall due to testing at home ( at a relatively low cost ) while fewer 
 tests are performed in clinic ( at higher cost ) .
cost and time parameters were varied 
 individually to examine effects on model results . in the probabilistic sensitivity analysis , 

these parameters were varied simultaneously , along with testing frequencies from 
 the daisy study , through their 95% confidence intervals , with values for each 
 parameter randomly chosen from distributions 10,000 times and cost - effectiveness 
 ratios calculated for each parameter set chosen .
uniform distributions , where all values in the range were equally likely 
 to be chosen , were used for time cost per hour , nonclinician direct costs for 
 clinic - based testing , and home - based testing costs .
gamma distributions , based on daisy study mean 
 and standard deviation ( sd ) data , were used for indirect monetary costs , time 
 required to receive care , and for clinician costs .
responses 
 to these questions were similar regardless of randomization group , therefore 
 results are reported for 388 subjects   ( 10 of the original 398 subjects had no 
 questionnaire data available ) .
slightly 
 more than one - fifth of subjects had no insurance , took more than 2 hours off school or work to attend 
 clinic , or traveled more that 30 minutes to attend clinic ; more than a third 
 paid for parking / transportation or had another person donate time so that care 
 could be obtained . costs 
 per test received are summarized in table 2 . 

direct costs for clinic - based testing , including clinician and test 
 costs , were estimated at 49 per test received . 

on average , subjects paid 2.97 for parking / transportation and 
 childcare , and 3.7 hours were spent by the subject and others to allow care to be received per clinic visit .
table 3 displays tests performed , testing costs , and cost - effectiveness results for 
 all study subjects and for subgroups based on recruitment site .
more tests and more asymptomatic tests were 
 performed among the home screening group ( p<.0001 ) , with greater differences 
 in testing rates seen in women recruited from neighborhoods .
women recruited from clinics had high testing 
 rates and a smaller differential between home and clinic - based testing .
no difference in std incidence was noted 
 between intervention groups ( 20.4 [ home testing ] versus 24.1 [ clinic testing ] per 
 100 woman - years , p=.28 ) .
considering total costs 
 for all subjects and all testing , and assuming equal std detection between 
 groups , the home testing intervention was cost saving , because fewer 
 clinic - based tests were performed and the resulting cost savings were not 
 completely offset by the costs of increased home testing ( table 3 ) .
total testing costs per infection found were 
 estimated at 702 in the intervention group and 717 in the control group .
however , cost savings were not noted for the neighborhood 
 recruitment subgroup , where each additional test obtained by the intervention 
 group compared to the control group cost about 24.50 , due to more frequent home - based 
 testing and no decrease in clinic testing with the intervention .
when only asymptomatic testing was considered 
 in all subjects , the intervention cost was 12.51 per additional test performed , since 
 the costs of increased home testing were not offset by the relativity small 
 decreases in clinic - based testing in the intervention group . in one - way 
 sensitivity analyses , four parameter values varied individually through their 
 listed ranges ( table 2 ) made the total cost per subject of all testing in the 
 intervention group greater than the total cost per subject in the control group ( table 4 ) .
the model was most sensitive to changes in home testing costs , with increases in this cost of 5 making the home testing intervention more expensive than clinic testing ; to have similar effects , time spent 
 seeking / receiving care , the cost of that time , or clinic testing cost would 
 need to decrease by about a third .
most 
 importantly , if infection detection frequency is not equal between groups , unlike 
 the equal detection seen in the daisy trial and assumed in this analysis , between - group differences 
 in infection costs and complication effects would need to be explicitly 
 accounted for in the analysis . in the 
 probabilistic sensitivity analysis , where all cost and testing parameters were 
 varied simultaneously , the intervention was cost saving in 52% of model 
 iterations when all testing was considered . 

when considering only asymptomatic testing , there was a 22% likelihood that 
 the intervention would be cost saving .
figure 1 
 illustrates the relationship of changes in testing rates to cost savings with a 
 home testing program if infection detection rates are equal between groups .
if per - patient clinic testing rates decrease 
 by more than 22.5% of the increase seen in home testing rates due to program 
 adoption , a home testing program will be cost saving .
for example , if a home 
 testing intervention increases home testing in a population by 1 test per 
 patient per year and decreases yearly clinic testing by 0.4 tests per patient 
 ( denoted by the 
x  in figure 1 ) , then the intervention would be cost 
 saving .
however , with the same increase 
 in home testing , if the clinic testing rate only decreases by 0.1 test per 
 patient ( denoted by the open square ) , then a home testing program is not cost 
 saving . in 
 this analysis of a program encouraging home testing for chlamydia and gonorrhea 
 in a high - risk group of young women
, we found that , when all costs and all 
 tests were considered , a home testing program was cost saving in the daisy study , 
 a randomized , controlled trial , while , at the same time , significant increases 
 in all tests and in asymptomatic tests were seen . however , whether cost savings occurred with 
 home testing depended on the patient group and clinical situation studied , 
 based on changes in clinic - based testing resulting from the intervention when std 
 detection is the same with either testing program .
cost savings were seen in clinic - recruited subjects , 
 a group that utilized clinic services more frequently , due to decreases in 
 clinic - based testing resulting from the availability of home testing . in subjects recruited from neighborhoods 
 surrounding the clinics , home testing was not cost saving , because of increased 
 home testing without proportionate clinic testing reductions or std detection improvements .
when only asymptomatic tests were considered , 
 home testing was again not cost saving .
finally , 
 the indirect costs of seeking or receiving care , that is , monetary costs for 
 childcare , parking , and other expenses ; time costs from missed work or school ; 
 and time donated by others were considerable and could present barriers to 
 receiving recommended testing and care . as suggested by 
 this analysis and by the daisy study itself ,
the decision to implement a home 
 testing intervention for chlamydia and gonorrhea is more complex than merely 
 seeking to maximize tests performed or to minimize costs .
home testing programs have been well 
 demonstrated to increase testing volume [ 13 ] , by decreasing some barriers to std testing 
 through the use of a relatively expensive test . 

unless direct costs incurred by individual clinics could be decreased as 
 a result of a home testing intervention , in times of budgetary limitations clinics 
 would have no incentive or means to implement such an intervention .
indirect cost savings ( when the intervention 
 is considered from the broader , societal standpoint ) and the public health 
 benefits of increased testing suggest that financial support for home testing 
 would need to come from higher levels for these societal benefits to be 
 obtained . for individual clinics with a 
 high proportion of frequently utilizing patients , a home testing intervention could 
 decrease the visit frequency by this patient group , increasing capacity for 
 other needed services and patient groups . 
 in different populations where care - related indirect costs might be 
 higher , for example
, due to clinic inaccessibility or unavailability , home 
 testing might prove more useful from clinical and economic standpoints by 
 increasing testing rates through decreasing individual disincentives for testing .
cost savings were not 
 seen when only asymptomatic tests are considered , implying that home testing 
 for screening purposes may not be economically favorable . however , the distinction of symptomatic and 
 asymptomatic testing might be somewhat artificial when a population is 
 considered , since the availability of home tests could have benefits beyond 
 those of screening . for example , delays 
 in seeking care when symptomatic are common , and the availability of home 
 testing may allow infections to be diagnosed sooner , potentially decreasing 
 untreated illness burden and pid risk .
no 
 differences in infection detection were seen between randomization groups in 
 the daisy study , where an urban population with relatively easy and frequent 
 access to care was investigated ; populations with less access could benefit 
 more from home screening .
finally , few 
 screening interventions are cost saving , with some cost per health benefit 
 gained absorbed by society or payers based on the magnitude of screening costs 
 and benefits gained . for example , hu 
 et al
.   found that annual chlamydia screening cost 2350 per quality adjusted life year gained compared to no screening and thus 
 would be considered very cost - effective compared to other health care 
 interventions . in our analysis , where equal 
 infection rates are seen between intervention groups , the cost per health 
 benefit gained depends on the benefits of greater testing frequency for infected 
 women and their partners .
unfortunately , 
 these benefits can not be estimated based on present data , a limitation of our 
 analysis .
a home testing 
 intervention for chlamydia and gonorrhea , while increasing testing rates , has 
 the potential to be cost saving when the direct and indirect costs of avoided 
 clinic visits are considered .
the cost 
 equation depends in large part on whether changes in clinic testing frequency and 
 std detection occur as a result .
home 
 testing effects on clinic testing frequency in other populations and on 
 individual and population health in localities with more limited health 
 services require further research .
 home testing for chlamydia and gonorrhea increases 
 screening rates , but the cost consequences of this intervention 
 are unclear . 
 we examined the cost differences between home - based 
 and clinic - based testing and the cost - effectiveness of home 
 testing based on the daisy study , a randomized controlled trial . 
 
 direct and indirect costs were estimated for home and clinic 
 testing , and cost - effectiveness was calculated as cost per 
 additional test performed . in the clinic testing group , direct 
 costs were 49/test and indirect costs ( the costs of seeking 
 or receiving care ) were 62/test . 
 home testing cost was 
 25/test . 
 we found that home testing was cost saving when all 
 testing for all patients was considered . 
 however cost savings were 
 not seen when only asymptomatic tests or when patient subgroups 
 were considered . 
 a home testing program could be cost saving , 
 depending on whether changes in clinic testing frequency occur 
 when home testing is available . 
1. INTRODUCTION
2. MATERIALS AND METHODS
3. RESULTS AND DISCUSSION
4. CONCLUSIONS