a prospective multicenter cohort study of 102 genetically confirmed children and adolescents with cf ( 48 males , 54 females ) aged 9.519.0 years was conducted over 24 months . all children underwent  paired testing ,  with ogtt and cgm and the initial ogtt used to classify children and adolescents with cf into three groups : ngt , igt , or cf - related diabetes based on world health organization criteria ( 8) . cgm ( medtronic minimed cgm gold ; medtronic diabetes , watford , u.k . ) was recorded at the start of the study ( cgm1 visit 1 ) and after a minimum of 12 months ( cgm2 visit 2 ) . after the ogtt was complete , the cgm device remained in situ in the home environment for 72 h on all patients . patients entered a minimum of four self - monitored blood glucose samples ( one touch ultra meter ; lifescan , milpitas , ca ) for daily cgm calibration . all data were extracted from the medtronic mini med solutions cgm sensor , mmt-730 version 3.0c ( 3.0.128 ) . validity of cgm in children and adolescents with cf was assessed by determination of reliability , reproducibility , and repeatability . reliability was assessed by bland - altman analysis of agreement ( 9,10 ) along with pearson 's correlation coefficient . reproducibility tested the null hypothesis that the mean difference between the coefficients of variation ( cvs ) of observations was zero using a paired student 's t test . repeatability was derived from bland - altman analysis and calculation of a discriminant ratio ( dr ) ( 11 ) . all data were extracted from the medtronic mini med solutions cgm sensor , mmt-730 version 3.0c ( 3.0.128 ) . mean and sd of the interstitial glucose concentrations for all cgm recordings were derived . validity of cgm in children and adolescents with cf was assessed by determination of reliability , reproducibility , and repeatability . reliability was assessed by bland - altman analysis of agreement ( 9,10 ) along with pearson 's correlation coefficient . reproducibility tested the null hypothesis that the mean difference between the coefficients of variation ( cvs ) of observations was zero using a paired student 's t test . repeatability was derived from bland - altman analysis and calculation of a discriminant ratio ( dr ) ( 11 ) . a total of 104 out of 160 children and adolescents with cf ( aged 9.519.0 years ) were studied . a total of 102 valid cgm results were obtained at cgm1 and 92 at cgm2 . the average number of valid cgm sensor readings used was 710 ( range 4991,410 ) . mean interstitial cgm glucose for all children and adolescents with cf was 6.7  2.3 mmol / l ( means  sd ) on cgm1 and 7.0  2.6 mmol / l cgm2 . mean interstitial cgm glucose for ngt , igt , and cf - related diabetes is shown in table 1 . all values were significantly higher than in normal healthy nondiabetic subjects ( mean 5.1  0.7 mmol / l , p < 0.0001 ) . validity of cgm at visit 1 ( cgm1 ) and visit 2 ( cgm2 ) in 102 children and adolescents with cystic fibrosis ( n = 102 ) data are mean  sd , percent , and dr . validity is based on reliability , reproducibility , and repeatability measures . * the baseline glucose tolerance category is based on standard oral glucose tolerance testing 2-h glucose concentrations : ngt < 7.8 , igt 7.811 , and cfrd > 11.1 ( 8) . normal healthy control subject data shown to be significantly different from all children and adolescents with cf ; bland and altman analysis revealed a mean difference between cgm glucose and ogtt glucose of 0.81  1.47 mmol / l with a 95% ci of the bias  2.90 mmol / l . a significant correlation was found between glucose measured by cgm and the blood glucose at five time points in a standard ogtt ( r = 0.740.91 , p < 0.01 ) . reproducibility was assessed by comparing cvs at five different time points of ogtt and within the subgroups ( table 1 ) . there were no significant differences in the cvs of the cgm assessment between visits , irrespective of glucose tolerance category . the drs ( the variability of an individual to the variability of the group ) for cgm1 and cgm2 were 13.0 and 15.1 , respectively . subgroup drs are shown in table 1 and indicate that cgm has the ability to identify subjects with high variability , such as cf - related diabetes , within this cohort of children and adolescents with cf . bland and altman analysis revealed a mean difference between cgm glucose and ogtt glucose of 0.81  1.47 mmol / l with a 95% ci of the bias  2.90 mmol / l . a significant correlation was found between glucose measured by cgm and the blood glucose at five time points in a standard ogtt ( r = 0.740.91 , p < 0.01 ) . reproducibility was assessed by comparing cvs at five different time points of ogtt and within the subgroups ( table 1 ) . there were no significant differences in the cvs of the cgm assessment between visits , irrespective of glucose tolerance category . the drs ( the variability of an individual to the variability of the group ) for cgm1 and cgm2 were 13.0 and 15.1 , respectively . subgroup drs are shown in table 1 and indicate that cgm has the ability to identify subjects with high variability , such as cf - related diabetes , within this cohort of children and adolescents with cf . bland and altman analysis revealed a mean difference between cgm glucose and ogtt glucose of 0.81  1.47 mmol / l with a 95% ci of the bias  2.90 mmol / l . a significant correlation was found between glucose measured by cgm and the blood glucose at five time points in a standard ogtt ( r = 0.740.91 , p < 0.01 ) . reproducibility was assessed by comparing cvs at five different time points of ogtt and within the subgroups ( table 1 ) . there were no significant differences in the cvs of the cgm assessment between visits , irrespective of glucose tolerance category . mmol / l with 95% ci for the difference of  0.46 mmol / l . the drs ( the variability of an individual to the variability of the group ) for cgm1 and cgm2 were 13.0 and 15.1 , respectively . subgroup drs are shown in table 1 and indicate that cgm has the ability to identify subjects with high variability , such as cf - related diabetes , within this cohort of children and adolescents with cf . this study demonstrates that cgm is a valid method for assessing glycemia in children and adolescents with cf , extending similar observations in adults with cf ( 7 ) . the validation of cgm in children and adolescents with cf is essential before other prospective research can be undertaken with cgm in children andadolescents with cystic fibrosis and is warrantedbecause of the higher glucose concentrations observed in these patients compared with the general population . as expected , there was a linear correlation between five - point ogtt plasma blood glucose and the corresponding cgm glucose readings ( r = 0.740.91 ) . rather than use correlation or clarke error grid analysis , which both describe association , we used bland - altman analysis of agreement ( 9,10 ) . mmol / l with a 95% ci  2.90 mmol / l , which is a reasonably acceptable bias for clinical practice . cgm was reproducible in children with cf with varying degrees of glucose intolerance , since there were no significant differences in the cvs of the cgm assessment between visits , irrespective of diagnosis . finally , we have demonstrated that cgm was repeatable as the mean difference between cgm1 , and cgm2 was 0.09 mmol / l . further , all drs were > 1 , indicating that cgm has the ability to discriminate between different subjects and allow comparison between subjects . in conclusion , cgm is a valid measure of glycemia in children and adolescents with cf . these observations suggest that cgm is not influenced by the cf chloride channel defect and has become a useful tool for the assessment of glycemia in children and adolescents with cf .
objectiveto validate continuous glucose monitoring ( cgm ) in children and adolescents with cystic fibrosis.research design and methodspaired oral glucose tolerance tests ( ogtts ) and cgm monitoring was undertaken in 102 children and adolescents with cystic fibrosis ( age 9.519.0 years ) at baseline ( cgm1 ) and after 12 months ( cgm2 ) . 
 cgm validity was assessed by reliability , reproducibility , and repeatability.resultscgm was reliable with a bland - altman agreement between cgm and ogtt of 0.81 mmol / l ( 95% ci for bias  2.90 mmol / l ) and good correlation between the two ( r = 0.740.9 ; p < 0.01 ) . 
 cgm was reproducible with no significant differences in the coefficient of variation of the cgm assessment between visits and repeatable with a mean difference between cgm1 and cgm2 of 0.09 
 mmol / l ( 95% ci for difference  0.46 mmol / l ) and a discriminant ratio of 13.0 and 15.1 , respectively.conclusionsin this cohort of children and adolescents with cystic fibrosis , cgm performed on two occasions over a 12-month period was reliable , reproducible , and repeatable .