4.0.0.0 CON­TIN­U­OUS GLU­COSE MON­I­TORS

4.1.0.0 In­tro­duc­tion

Rec­om­men­da­tions

7.10 Sen­sor-‍aug­ment­ed pump ther­a­py may be con­sid­ered for chil­dren, ado­les­cents, and adults to im­prove glycemic con­trol with­out an in­crease in hy­po­glycemia or se­vere hy­po­glycemia. Benefits cor­re­late with ad­her­ence to on­go­ing use of the de­vice. A

7.11 When pre­scrib­ing con­tin­u­ous glu­cose mon­i­tor­ing, ro­bust di­a­betes ed­u­ca­tion, train­ing, and sup­port are re­quired for op­ti­mal con­tin­u­ous glu­cose mon­i­tor im­ple­men­ta­tion and on­go­ing use. E

7.12 Peo­ple who have been suc­cess­ful­ly using con­tin­u­ous glu­cose mon­i­tors should have con­tin­ued ac­cess across third-‍party pay­ers. E

CGM mea­sures in­ter­sti­tial glu­cose (which cor­re­lates well with plas­ma glu­cose). There are two types of CGM de­vices. Most CGM de­vices are real-‍time CGM, which con­tin­u­ously re­port glu­cose lev­els and in­clude alarms for hy­po­glycemic and hy­per­glycemic ex­cur­sions. The other type of de­vice is in­ter­mit­tent­ly scan­ning CGM (isCGM), which is ap­proved for adult use only. isCGM, dis­cussed more fully below, does not have alarms and does not com­mu­ni­cate con­tin­u­ously, only on de­mand. It is re­ported to have a lower cost than sys­tems with au­to­mat­ic alerts.

For some CGM sys­tems, SMBG is re­quired to make treat­ment de­ci­sions, al­though a ran­dom­ized con­trolled trial of 226 adults sug­gest­ed that an en­hanced CGM de­vice could be used safe­ly and ef­fec­tive­ly with­out reg­u­lar confirma­to­ry SMBG in pa­tients with well-‍con­trolled type 1 di­a­betes at low risk of se­vere hy­po­glycemia (59). Two CGM de­vices are now ap­proved by the FDA for mak­ing treat­ment de­ci­sions with­out SMBG confirma­tion, some­times called ad­junc­tive use (60,61).

The abun­dance of data pro­vided by CGM of­fers op­por­tu­ni­ties to an­a­lyze pa­tient data more gran­u­lar­ly than was pre­vi­ous­ly pos­si­ble, pro­vid­ing ad­di­tion­al in­for­ma­tion to aid in achiev­ing glycemic tar­gets. A va­ri­ety of met­rics have been pro­posed (62). As re­cent­ly re­ported, the met­rics may in­clude: 1) av­er­age glu­cose; 2) per­cent­age of time in hy­po­glycemic ranges, i.e., <54 mg/dL (level 2), 54–70 mg/dL (level 1) (62); 3) per­cent­age of time in tar­get range, i.e., 70–180 mg/dL (3.9–9.9 mmol/‍L); 4) per­cent­age of time in hy­per­glycemic range, i.e., ≥180 mg/dL (62). To make these met­rics more ac­tionable, stan­dardized re­ports with vi­su­al cues, such as an am­bu­la­to­ry glu­cose profile (62), may help the pa­tient and the pro­vider in­ter­pret the data and use it to guide treat­ment de­ci­sions.

In ad­di­tion, while A1C is well es­tab­lished as an im­por­tant risk mark­er for di­a­betes com­pli­ca­tions, with the in­creas­ing use of CGM to help fa­cil­i­tate safe and ef­fective di­a­betes man­agement, it is im­por­tant to un­der­stand how CGM met­rics, such as mean glu­cose and A1C cor­re­late. Es­ti­mat­ed A1C (eA1C) is a mea­sure con­vert­ing the mean glu­cose from CGM or self-‍mon­i­tored blood glu­cose read­ings, using a for­mu­la de­rived from glu­cose read­ings from a pop­u­la­tion of in­di­vid­u­als, into an es­ti­mate of a si­mul­ta­ne­ous­ly mea­sured lab­o­ra­to­ry A1C. Re­cent­ly, the eA1C was re­named the glu­cose man­agement in­di­ca­tor (GMI), and a new for­mu­la was gen­er­at­ed for con­vert­ing CGM-‍de­rived mean glu­cose to GMI based on re­cent clin­i­cal tri­als using the most ac­cu­rate CGM sys­tems avail­able. This pro­vided a new way to use CGM data to es­ti­mate A1C (63).