If you've got plenty of time, you'll find this section much better explained here. But please, trust me, in 3-5 minutes you'll find the gist of it reading this post.
HBA1C
- ADA recommends, with no scientific evidence whatsoever, to perform A1c every 6 months if glycemic targets (see later) are met, or every 3 if not.
- A1c could be (not clear) a little higher in people of African origin. Some genetic variants could lead to lower values, like HbS (-0.3%) or GDPDH deficiency (-0.8%).
- A1c(%)-SMBG (mg/dL) correlations are: 5-97, 6-126, 7-154, 8-183, 9-212, 10-240, 11-269. They're easy to memorize and very useful in clinical practice.
GLYCEMIA
- Self-monitored blood glycemia (SMBG) and continued glucose monitoring (CGM) are key for diabetes control. It helps evaluating efficacy of therapies and lifestyle, like foods, physical activities, and other.
- CGM results must be presented in a validated and standarized way that includes:
- Number of evaluated days (recommended >=14)
- % time device is measuring (rec. >70%)
- Mean glycemia
- Variability (rec. <36%)
- GMI Glucose Management Indicator
- % time >250 mg/dL (Time Above Range TAR level 2)
- % time >180 mg/dL (Time Above Range TAR level 1)
- % time 70-180 mg/dL (Time in Range TIR)
- % time <70 mg/dL (Time Below Range TBR level 1)
- % time <54 mg/dL (Time Below Range TAR level 2)
A1C AND GLYCEMIC GOALS
Leaving apart pregnants, older adults and children and adolescents, main goals are:
- <7% as a general rule. That means pre-prandial values of 80-130 and peak post-prandial <180 mg/dL. Before 2015 pre-prandial suggested values were 70-130.
- <6,5% if can be achieved safely, without hypogluycemia or adverse effects
- <8% in these cases:
- History of severe hypoglycemia
- Limited life expectancy
- Advanced micro or macrovascular complications
Rationale:
Microvascular complications
- DCCT, Kumamoto and UKPDS trial showed that lowering A1c is associated to reduction of microvascular disease, particularly at high A1c levels.
- Reducing A1c <7% is also beneficial as to microangiopathy, but not so much, and sometimes at the expense of hypoglycemia (T1D) or polypharmacy (T2D), and is only cost-effective if can be safely achieved.
- In diabetes >10 years with macrovascular disease, ACCORD, VADT and ADVANCE trials showed that microvascular benefits of lowering A1c <7% do not make up for mortality costs and is not recommended.
Macrovascular disease
- In T1D (DCCT), as well asrecently diagnosed T2D (UKPDS), A1c reduction lead to CVD event reduction.
- In advanced T2D, A1c reduction does not reduce CVD nor mortality. Hypoglycemia must be avoided, and GLP-RAs and SGLT2-1 are recommended in established CVD because they reduce CV events and mortality.
Postprandial glycemia
- Although post-prandial peak is correlated to CV disease, intervention studies have not showed that its reduction has CV benefits beyond A1c reduction
- The closer to 7% A1c is, the highest contribution postprandial glycemia has. So, in cases with A1c around 7%, to improve control, focus in reducing PP glucose.
HYPOGLYCEMIA
- Hypoglycemia is classified in 3 levels:
- Level 1: <70 mg/dL, it is the level for contrarregulatory response
- Level 2: <54 mg/dL, it is the level for neuroglycopenia. Asymptomatic level 2 hypoglucemia strongly suggests HU (failure of contraregulatory and autonomic response).
- Level 3: need assistance irrespective of glycemia.
- Fasting, delayed meals, alcohol, exercise, and sleep are precipitants for hypos.
- Patients at risk for hypo (insulina, secretagogues) should be screened for hypoglycemia unawareness (HU)
- Glucagon must be prescribed for patiens at risk for level 2 (severe) hypoglycemia. Apart from glucagon powder, intranasal and SC solutions have been recently approved by FDA.
- Patients with history of level 3 hypo, HU or several level 2 hypos should relax A1c for several weeks to avoid HU.
- Patients with cognitive impairment must be screened for hypoglycemia and monitored for cognitive progression. In older subjects with DM, level 3 hypoglycemia is associated with CogImp, but not in DCCT population: Causal relation is not clear.
- Concious patients with glycemia <70 mg/dL must be treated with 15-20 g of oral glucose, although other glucose-containing CH are also useful, although not protein-rich food in type 2 diabetes because it raises insulin secretion. In any case, glycemia should be monitored in 15 min, and treatment repeated if not resolved. after resolution, eat a snack.
- Hypoglycemia training programs must be provided to patients with level 3 hypo or HU.
- In T1D, Real-Time CGM reduces time spent in range 54-70 mg/dL (level 1 hypo) but not in level 3. Little data are for flash devices and for type 2 diabetes.
INTERCURRENT ILLNESS
- Acute events like illness, surgery, trauma, raise glycemia and may precipitate DKA or NHH.
- Glycemia and, if indicated, ketonemia must be frequently measured
- Glycemia correction, usually with insulin, even in non-insulin dependent individuals, as well as adequate nutrition and hydration, is neccesary.
- Hospitalization for acute illness is more frequent in diabetes than in individuals without it. For correct in-hospital care see here.
