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New CGM Targets – Pregnant Women and High-Risk Patients

Dec 31, 2019
 
Editor: David L. Joffe, BSPharm, CDE, FACA

Author: Nour Salhab, Pharm.D. Candidate, USF College of Pharmacy

Getting patients to new standard CGM targets will prevent complications and hypoglycemia.

Continuous glucose monitoring (CGM) has been integrated into the health system for the past few years. It is convenient to use, which can increase adherence and help guide therapy. However, clear targets are yet to be established. As we know, our standard of care is HbA1c. While it is helpful to determine how controlled a patient with diabetes is, it is still limited because of the lack of information about glucose variations. Conditions such as anemia, iron deficiency, pregnancy, and hemoglobinopathies can alter HbA1c.

In contrast, CGM can assess glucose variability and identify patterns of hypoglycemia and hyperglycemia. The utility of CGM, in addition to HbA1c, will help guide therapy. This article will summarize the latest monitoring recommendations.

Key CGM measurements include the percentage of readings and time per day within the target glucose range (TIR), time below target glucose range (TBR), And time above target glucose range (TAR). These targets must be personalized to meet every patient’s need to adjust therapy and prevent side effects and diabetes complications. The percentage of CGM readings or time per day is a way to track these targets. The proposed standardized report lets clinicians determine the percentage of time spent within, below, and above each patient’s range to allow for individualization and shared decision making. With the standardized report, the clinician will be able to use the glucose management indicator metric to view possible discrepancies and compare them to the patient’s HbA1c.

The group reached a consensus on glycemic cut points for pregnant patients, which is a range of 70 to 180 mg/dL for individuals with type one diabetes and 63 to 140 mg/dL for patients with type 2 diabetes. The goal in pregnant patients is to lower the TIR as quickly as possible while reducing the TAR and glycemic variability. However, stringent targets are needed to prevent outcomes and hypoglycemia. For older and high-risk patients, the TIR target has been lowered from >70% to >50%, and TBR has been reduced to <1% at <70 mg/dL to reduce the likelihood of hypoglycemia. For patients who are 25 years or younger, it is recommended to aim for the lowest achievable HbA1c without the burden of care or the risk of hypoglycemia. An Hb1c target of 7% is preferred. This target equals a TIR target of about 60%. Regarding complications, as TIR decreases, the likelihood of diabetic retinopathy and microalbuminuria increases. An increase in TIR of 10% will approximately result in a 0.5% reduction in HbA1c.

Future studies should focus on CGM targets for women with gestational diabetes and type 2 diabetes mellitus. Additionally, longer-term studies are needed to observe time spent within range, diabetes complications, and other outcomes.

Practice Pearls:

  • It is important to get pregnant women with diabetes to the target of TIR 63-140 mg/dL at >70%; TBR <63 mg/dL at <4%; TAR >140 mg/dL at <25%
  • For older and/or high-risk patients, TIR 70-180 mg/dL at >50%; TBR <70 mg/dL at <4%; TAR >180 mg/dL at <25%
  • For patients with T1DM/T2DM, the target of TIR 70-180 mg/dL at >70%; TBR <70 mg/dL at <1%; TAR >250 mg/dL at <10%
  • It is vital to work with each patient to personalize their own targets to get them to therapeutic ranges safely and effectively.

Battelino, Tadej, et al. “Clinical Targets for Continuous Glucose Monitoring Data Interpretation: Recommendations From the International Consensus on Time in Range.” Diabetes Care, vol. 42, no. 8, 2019, pp. 1593–1603.

Nour Salhab, Pharm.D. Candidate, USF College of Pharmacy