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Prediabetes and Diabetes Type 2: Screening and Making the Diagnosis

Clinical Actions:

Diabetes results from the impaired secretion of insulin or resistance to its peripheral effects, leading to abnormal metabolism of carbohydrates and elevated levels of glucose in the blood and urine. Type 2 diabetes (previously “noninsulin-dependent diabetes” or “adult-onset diabetes”) accounts for 90–95% of all diabetes. Type 2 diabetes is caused by a progressive loss of β-cell insulin secretion, usually associated with insulin resistance. Prediabetes is diagnosed when glucose levels start to rise due to β-cell insulin secretion failure, but diagnostic criteria are not yet met for Type 2 diabetes.

Table of Contents  

Evaluate Patients for Risk Factors

Risk Factors for Type 2 Diabetes (NIDDK)

  • Overweight or obese
    • NIDDK BMI chart (see ‘Primary Sources – Learn More’ below)
      • Not Asian American or Pacific Islander: At-risk BMI ≥ 25
      • Asian American: At-risk BMI ≥ 23
      • Pacific Islander: At-risk BMI ≥ 26
  • ≥45 years
  • Family history of diabetes
  • Race/Ethnicity
    • African American, Alaska Native, American Indian, Asian American, Hispanic/Latino, Native Hawaiian, or Pacific Islander
  • Hypertension (or on therapy for hypertension)
  • Dyslipidemia
  • Personal history of
    • Pregnancy: GDM or macrosomia (BW >4000 g)
    • Physical inactivity
    • Heart disease or stroke
    • Depression
    • PCOS
    • Acanthosis nigricans
    • HIV

Screening and Diagnostic Criteria

Who and When to Screen

ADA

  • Overweight or obesity (BMI ≥25 kg/m2 or ≥23 kg/m2 in Asian Americans) and ≥1 of the following risk factors
    • First-degree relative with diabetes
    • High-risk race/ethnicity (e.g., African American, Latino, Native American, Asian American, Pacific Islander)
    • History of CVD
    • Hypertension (≥140/90 mmHg or on therapy for hypertension)
    • HDL cholesterol level <35 mg/dL (0.90 mmol/L) and/or a triglyceride level >250 mg/dL (2.82 mmol/L)
    • Women with polycystic ovary syndrome
    • Physical inactivity
    • Other clinical conditions associated with insulin resistance (e.g., severe obesity, acanthosis nigricans)
  • People with HIV
    • Screen for diabetes and prediabetes with a fasting glucose test
      • Before starting antiretroviral therapy
      • At the time of switching antiretroviral therapy
      • 3 to 6 months after starting or switching antiretroviral therapy
    • If initial screening results are normal, fasting glucose should be checked annually
  • Patients with prediabetes (A1C ≥5.7% [39 mmol/mol], IGT, or IFG) should be tested yearly
  • Women who were diagnosed with GDM should have lifelong testing at least every 3 years
  • For all other patients, testing should begin at age 35 years
  • If results are normal, testing should be repeated at a minimum of 3-year intervals, with consideration of more frequent testing depending on initial results and risk status

AACE/ACE

  • Begin at age 45 without risk factors
  • Screening based on risk factors: In addition to the above list, AACE/ACE includes the following factors
    • Antipsychotic therapy for schizophrenia and/or severe bipolar disease
    • Chronic glucocorticoid exposure
    • Sleep disorders (e.g., obstructive sleep apnea, chronic sleep deprivation, and night shift occupation) with glucose intolerance
  • Normal glucose values: Every 3 years
  • Consider annual screening for patients with 2 or more risk factors

USPSTF

  • Screen for prediabetes and type 2 diabetes in adults aged 35 to 70 years who have overweight (BMI ≥25) or obesity (BMI ≥30)
  • Clinicians should offer or refer patients with prediabetes to effective preventive interventions
  • Above are Grade B recommendations: Offer or provide this service

Diagnostic Criteria

  • Normal
    • Fasting plasma glucose (FPG) <100 mg/dL (5.6 mmol per L)
    • Oral glucose tolerance test (OGTT) with 75g glucose load
      • 2h (plasma glucose) PG <140 mg/dL (7.8 mmol per L)
  • High Risk for Diabetes (prediabetes)
    • Impaired fasting glucose (IFG): FPG ≥100 to 125 mg/dL (5.6 to 6.9 mmol per L)
    • Impaired glucose tolerance (IGT): 2h PG ≥140 to 199 mg/dL (7.8 to 11.0 mmol per L)
    • A1C 5.7% to 6.4%
    • Note: Patients with prediabetes should be tested yearly
  • Diabetes: Glucose criteria are preferred for the diagnosis of DM
    • FPG ≥126 (7.0 mmol per L) mg/dL
    • OGTT: 2h PG ≥200 mg/dL (11.1 mmol per L)
    • Random PG ≥200 mg/dL (11.1 mmol per L) with the following symptoms of hyperglycemia
      • Polydipsia | Polyuria | Polyphagia | Blurred vision | Weakness | Unexplained weight loss
    • A1C ≥6.5%
    • Note: Always confirm diabetes diagnosis with repeat glucose or A1C testing on another day

SYNOPSIS:

Prediabetes is not a clinical disorder but rather an important risk factor for diabetes and cardiovascular disease. While there are some differences between organizations regarding risk factors for screening and diagnostic cut-offs, all agree as to the importance of identifying those at risk for significant cardiovascular events if diabetes is left untreated. The prognosis for type 2 diabetes varies and is very dependent on glucose control.

KEY POINTS:

Symptoms of Diabetes (related to hyperglycemia)

  • Excessive urination, thirst and hunger 
  • Unexpected weight loss 
  • Increased susceptibility to infections, especially yeast or fungal infections 
  • Weak, tired feeling
  • Dry mouth
  • Blurry vision
  • Deposits of blood, or puffy yellow spots in the retina
  • Decreased sensation in the legs
  • Weak pulses in the feet
  • Blisters, ulcers or infections of the feet 

Complications of Type 2 Diabetes

  • Atherosclerosis
  • Retinopathy 
  • Neuropathy 
  • Nephropathy
  • Dermatologic pathology
    • Infections
    • Feet in particular: Ulcerations with poor healing  

Learn More – Primary Sources:

ADA Standars of Care in Diabetes 2024 

AACE Comprehensive Type 2 Diabetes Mellitus Care Algorithm  

NIDDK: Risk Factors for Type 2 Diabetes 

60-Second Type 2 Diabetes Risk Test 

USPSTF: Screening for Prediabetes and Type 2 Diabetes 

HIV and Diabetes | NIH